Method and unit for end sealing elongated wrappings

Abstract: Elongated wrappings (2) made of sheet material comprising a first metal component (4) and a second heat-sealable component (5) are end sealed by successively feeding the wrappings (2), by means of a conveyor (6), in a first given direction (8) and along a given path (9) through a sealing station (10); varying the traveling speed of the wrappings (2) in relation to the conveyor (6) at the sealing station (10); and induction heating, for a given length of time during a relative pause, the first component (4) at the ends (23) of each wrapping (2), to melt the second component (5).

Description: The present invention relates to a method of end sealing elongated wrappings. GB-A-2229156 discloses a unit for end closing elongated tubular wrappings, wherein each tubular wrapping is mated with a relevant seat arranged on a drum conveyor rotating at substantially constant speed about its axis for successively feeding the tubular wrappings in a first given direction and along a given path extending through an end closing station having a closing device arranged in a fixed position. At the end closing station, the traveling speed of each tubular wrapping is varied in relation to the drum conveyor by oscillating the relevant seat in respect to the drum conveyor to substantially stop the tubular wrapping in respect to the closing device. Since the aforementioned closing device is arranged in a fixed position, each seat is kept in a substantially fixed position (which is not a totally fixed position very difficult to obtain) in relation to the end closing device for the time period during which this device engages the tubular wrapping carried by the relevant seat. In practice, each seat vibrates about the aforementioned fixed position when the relevant tubular wrapping is engaged by the closing device, but this vibration is not detrimental since mechanical end closing devices do not need absolute precision for good operation. However, the aforementioned unit cannot be used with a heating end closing device, which needs to be maintained precisely in a given position in respect to a relevant tubular wrapping during the heat sealing of the ends of such wrapping. More specifically, the present invention relates to a straightforward, effective method of end heat-sealing elongated wrappings fed by a conveyor along a given path and made of sheet material comprising a metal component and a heat-sealable component. The present invention is particularly suitable for use in the food industry, for end sealing elongated, not necessarily cylindrical, wrappings or so-called "sticks" on wrapping machines, to which the following description refers purely by way of example. According to the present invention, there is provided a method of end sealing elongated wrappings made of sheet material comprising a first metal component and a second heat-sealable component; the method comprising the steps of mating each wrapping with a relevant grip arranged on a drum conveyor; successively feeding the wrappings in a first given direction and along a given path extending through an end sealing station by rotating said drum conveyor at substantially constant speed about its axis; and varying the traveling speed of each wrapping in relation to the drum conveyor at the sealing station by oscillating the relevant grip in respect to the drum conveyor; characterized in that it further comprises the steps of imparting, at the sealing station, to each wrapping a movement along a trajectory extending in a second direction substantially radial in relation to the drum conveyor; moving at least one sealing head, arranged at said sealing station, to and from a respective end of a relevant wrapping, as well as along said trajectory; and heating, by means of said sealing head and at said sealing station, said end of the wrapping for a given length of time, to melt said second component at said end and seal the end itself. The present invention also relates to a unit for end sealing elongated wrappings. According to the present invention, there is provided a unit for end sealing elongated wrappings made of sheet material comprising a first metal component and a second heat-sealable component; the unit comprising grips, each of which is able to house a respective said wrapping; a drum conveyor supporting said grips and rotating at substantially constant speed about its axis for successively feeding the wrappings housed in said grips in a first given direction and along a given path; an end sealing station located along said path; and speed varying means for varying the traveling speed of each wrapping in relation to the drum conveyor at the sealing station by oscillating the relevant grip in respect to the drum conveyor; characterized by further comprising second actuating means interposed between the drum conveyor and each said grip, and for so oscillating the grip that, in use and at the sealing station, the respective wrapping travels along a trajectory extending in a second direction substantially radial in relation to the drum conveyor; at least one sealing head arranged at said sealing station; actuating means for moving said sealing head to and from a respective end of a relevant wrapping, as well as along said trajectory; and heating means arranged on said sealing head for heating an end of a relevant wrapping for a given length of time, to melt said second component at said end and seal the end itself. A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a schematic side view, with parts removed for clarity, of a preferred embodiment of the sealing unit according to the present invention; Figure 2 shows a larger-scale detail of Figure 1; Figure 3 shows a section along line III-III in Figure 2. Number 1 in the accompanying drawings indicates a unit for end sealing normally, but not necessarily, cylindrical elongated wrappings 2 presenting a longitudinal axis 3, and made of sheet material comprising a metal layer 4, preferably of foil, and a cover layer 5 of heat-sealable material, preferably lacquer. Unit 1 comprises a conveyor drum 6 rotating at substantially constant angular speed about its axis 7 to successively feed wrappings 2 in a given direction 8 and along an annular path 9 extending through a sealing station 10 where wrappings 2 are end sealed. As shown clearly in Figure 1, drum 6 comprises a number of grips 11 connected to it in rotary manner by respective pins 12 parallel to, and equally spaced along a circumference coaxial with, axis 7. At its free end opposite that connected to respective pin 12, each grip 11 defines a seat 13 for receiving a respective wrapping 2 with its axis 3 parallel to axis 7; and each grip 11 forms part of a speed varying device 14 comprising a fixed cam 15 with an annular face groove 16 extending about axis 7. For each grip 11, device 14 also comprises a lateral lever 17 integral with grip 11 and fitted on its free end, a given distance from respective pin 12, with a tappet roller 18 rotating, in relation to respective lever 17, about its axis parallel to axis 7, and engaged in rolling manner inside groove 16. As shown in Figure 1, to maintain grips 11 in a substantially radial position in relation to drum 6, groove 16 is substantially circular, except for a portion in the region of station 10 where groove 16 is so shaped as to first rotate each grip 11 about pin 12 in the same direction as drum 6 about axis 7, and then rapidly rotate each grip 11 in the opposite direction to drum 6, so as to cause, for a given length of time at station 10, a pause in the movement of seat 13 in direction 8. Since pin 12 of each grip 11 continues to rotate continuously about axis 7 even during the pause of respective seat 13, this, during the pause, acts as a link which travels back and forth along a trajectory 19 extending outwards from path 9 in a direction 20 substantially perpendicular to direction 8 at station 10. In practice, trajectory 19 extends along an arc, the axis 21 of which is parallel to axis 7 and located outside the circle defined by path 9. At station 10, drum 6 cooperates with an end sealing device 22 which, as shown in Figure 3, cooperates with opposite ends 23 (only one shown) of wrapping 2 to end seal the wrapping. Device 22 comprises a fixed support 24 located outwards of the outer periphery of drum 6, and presenting a cylindrical through hole 25 coaxial with axis 21 and engaged in rotary manner by a through sleeve 26. Each end of sleeve 26 projects from hole 25, and is fitted with a radial appendix 27, the free end of which is fitted with a respective movable sealing element 30 (only one shown) by means of a hinge 28 presenting an axis 29 crosswise to axis 21. As sealing elements 30 are specularly identical, are located on either side of, and move simultaneously and in the same manner in relation to, drum 6, only one element 30 will be described. In this connection, it should be pointed out that certain wrappings 2 present only one end 23 for sealing, in which case, device 22 comprises only one movable sealing element 30. Element 30 comprises an arm 31 connected at one end to appendix 27 by hinge 28, extending along an axis 32 perpendicular to axis 21 and crosswise to axis 29, and facing the relative end of sleeve 26. On the side opposite that facing sleeve 26, arm 31 is fitted with a casing 33 with which it defines a chamber 34 extending along axis 32. At the opposite end to that connected to appendix 27, arm 31 presents a through hole 35 with an axis 36 perpendicular to axis 32, and which receives in axially-sliding manner, in opposition to a Belleville washer 37 cooperating with casing 33, a cylindrical block 38 forming the base of an induction sealing head 39 located at station 10. Head 39 comprises a ferrite core 40 coaxial with axis 36; a winding 41 wound about core 40 and in turn comprising a copper tube 42 defining the end portion of a cooling fluid, e.g. air, circuit 43 for maintaining head 39 within a given temperature; and a cap 44, preferably made of synthetic material, and for preventing direct contact between core 40 and wrappings 2. Tube 42 comprises an input portion 45 and an output portion 46, both extending along chamber 34 and connected to opposite poles of a mains-connected control unit 47, the first directly, and the second via at least a condenser 48 housed inside a chamber 49 formed in the thickness of arm 31 and communicating with chamber 34. As shown, particularly in Figure 2, appendix 27 presents a lateral arm 50, the free end of which is possibly integral with the corresponding arm 50 (not shown) of the other element 30 (if provided), and is connected, by a hinge 51 with an axis parallel to axis 21, to the free end of the output rod of an axial actuator 52 for rotating sleeve 26 and arm 31 about axis 21 by such a given maximum angle as to enable head 39 to travel both ways along trajectory 19 at station 10. An intermediate portion of arm 31 presents a further through hole 53 coaxial with axis 21 and housing in a fixed position a cup-shaped body 54; one end of body 54, partly engaged inside sleeve 26, is closed by an end wall 55 presenting a hole 56 coaxial with axis 21 and engaged in axially-sliding manner by a rod 57; and an intermediate portion of rod 57 is fitted with a plate 58 sliding inside body 54 in opposition to a damping spring 59 interposed between plate 58 and end wall 55. At the end facing arm 31, rod 57 presents a tip 60 cooperating frontally with a cover 61 fitted to arm 31 to close the end of hole 53 facing casing 33. Rod 57 forms a link of a double-link actuating crank mechanism 62 comprising a double crank 63 housed inside sleeve 26 and oscillated by a drive shaft (not shown) about an intermediate axis 64 perpendicular to axis 21; and two connecting rods 65 hinged to opposite ends of double crank 63 and respectively connected to the end of rod 57 opposite that presenting tip 60, and to the other rod 57 (not shown) of the other element 30 (not shown) if provided. In actual use, as each wrapping 2 arrives at station 10, control unit 47 activates head 39 to supply a given current through winding 41 and generate, at station 10, a variable magnetic field capable of inducing, in layer 4 of wrapping 2 at station 10, sufficient current to heat layer 4 and melt the heat-seal material of layer 5 to end seal wrapping 2. To ensure perfect sealing, as each wrapping 2 enters station 10, element 30 is oscillated by actuator 52 in direction 20 and about axis 21 to enable sealing head 39 to accompany wrapping 2 as it travels along trajectory 19. At the same time, element 30 is also oscillated by crank mechanism 62 in a further direction 66, crosswise to direction 20, and to and from path 9, to enable head 39 to move parallel to axis 3 and to and from the respective end 23 of wrapping 2. The above method and unit are equally applicable in the event wrapping 2, more generally speaking, presents at least one layer of material comprising a metal or conductive component and a heat-sealable component.

Claims: A method of end sealing elongated wrappings (2) made of sheet material comprising a first metal component (4) and a second heat-sealable component (5); the method comprising the steps of mating each wrapping (2) with a relevant grip (11) arranged on a drum conveyor (6); successively feeding the wrappings (2) in a first given direction (8) and along a given path (9) extending through an end sealing station (10) by rotating said drum conveyor (6) at substantially constant speed about its axis (7); and varying the traveling speed of each wrapping (2) in relation to the drum conveyor (6) at the sealing station (10) by oscillating the relevant grip (11) in respect to the drum conveyor (6); characterized in that it further comprises the steps of imparting, at the sealing station (10), to each wrapping (2) a movement along a trajectory (19) extending in a second direction (20) substantially radial in relation to the drum conveyor (6); moving at least one sealing head (39), arranged at said sealing station (10), to and from a respective end (23) of a relevant wrapping (2), as well as along said trajectory (19); and heating, by means of said sealing head (39) and at said sealing station (10), said end (23) of the wrapping (2) for a given length of time, to melt said second component (5) at said end (23) and seal the end (23) itself. A method as claimed in Claim 1, characterized in that each grip (11) feeds a respective wrapping (2) crosswise to the longitudinal axis of the wrapping (2); said sealing head (39) being oscillated in two substantially Perpendicular directions (66, 20) to move it, parallel to the longitudinal axis (3) of the wrapping (2), to and from the respective said end (23) of each said wrapping (2), as well as along said trajectory (19). A method as claimed in Claim 1 or 2, characterized in that said step of heating at least one end (23) of the wrapping (2) is performed by means of heating said first component (4) by magnetic induction. A unit for end sealing elongated wrappings (2) made of sheet material comprising a first metal component (4) and a second heat-sealable component (5); the unit (1) comprising grips (11), each of which is able to house a respective said wrapping (2); a drum conveyor (6) supporting said grips (11) and rotating at substantially constant speed about its axis (7) for successively feeding the wrappings (2) housed in said grips (11) in a first given direction (8) and along a given path (9); an end sealing station (10) located along said path (9); and speed varying means (14) for varying the traveling speed of each wrapping (2) in relation to the drum conveyor (6) at the sealing station (10) by oscillating the relevant grip (11) in respect to the drum conveyor (6); characterized by further comprising second actuating means (15-18) interposed between the drum conveyor (6) and each said grip (11), and for so oscillating the grip (11) that, in use and at the sealing station (10), the respective wrapping (2) travels along a trajectory (19) extending in a second direction (20) substantially radial in relation to the drum conveyor (6); at least one sealing head (39) arranged at said sealing station (10); actuating means (62, 52) for moving said sealing head (39) to and from a respective end (23) of a relevant wrapping (2), as well as along said trajectory (19); and heating means (41) arranged on said sealing head (39) for heating an end (23) of a relevant wrapping (2) for a given length of time, to melt said second component (5) at said end (23) and seal the end (23) itself. A unit as claimed in Claim 4, characterized in that each grip (11) feeds a respective wrapping (2) crosswise to the longitudinal axis of the wrapping (2); said induction sealing head (39) being mounted so as to oscillate in relation to the drum conveyor (6) about two axes (29, 21), a first (29) of which is crosswise and a second (21) parallel to the axis (7) of the drum conveyor (6); first actuating means (62) being provided to move said head (39), parallel to the longitudinal axis (3) of the wrapping (2), about said first axis (29) and to and from the respective said end (23) of each said wrapping (2); and second actuating means (52) being provided to move said head (39) about said second axis (21) and along said trajectory (19). A unit as claimed in Claim 4 or 5, characterized in that said heating means (41) are magnetic induction heating means. A unit as claimed in Claim 6, characterized in that characterized in that said heating means (41) comprises at least an electric winding (41) defined by a coiled electrically conductive tube (42). A unit as claimed in Claim 7, characterized in that said tube (42) forms part of a heat-exchange fluid circuit (43).

Inventors: BERTI ANDREA, SPATAFORA MARIO, BERTI, ANDREA, SPATAFORA, MARIO
Applicants: AZIONARIA COSTRUZIONI ACMA SPA, AZIONARIA COSTRUZIONI MACCHINE AUTOMATICHE-A.C.M.A.-S.P.A.
Application year: 1996
Main classification: B65B51
IPC codes: B29C65, B65B51