[0001] The present invention relates to a forming and sealing unit for a packaging machine
for packaging pourable food products.
[0002] Machines for packaging pourable food products, such as fruit juice, wine, tomato
sauce, pasteurized or long-life (UHT) milk, etc., are known in which the packages
are formed from a continuous tube of packaging material defined by a longitudinally
sealed web.
[0003] The packaging material has a multilayer structure comprising a layer of paper material
coated on both sides with layers of heat-seal material, e.g. polyethylene. For aseptic
packaging of preserved products such as UHT milk, the packaging material comprises
a layer of barrier material defined, for example, by an aluminium foil, which is superimposed
on a layer of heat-seal plastic material and is in turn coated with another layer
of heat-seal plastic material defining the inner face of the package contacting the
food product.
[0004] Aseptic packages are produced by unwinding the web of packaging material off a roll
and through an aseptic chamber, where it is sterilized, for example, by applying a
sterilizing agent such as hydrogen peroxide, which is subsequently evaporated by heating,
and/or by subjecting the packaging material to radiation of appropriate wavelength
and intensity. The sterilized web is then folded into a cylinder and sealed longitudinally
to form, in known manner, a continuous vertical longitudinally sealed tube. That is,
the tube of packaging material forms an extension of the aseptic chamber, and is filled
continuously with the pourable food product and fed to a forming and (transverse)
sealing unit for forming the individual packages, and which grips the tube between
pairs of jaws for transversely sealing the tube into pillow packages.
[0005] The pillow packages are separated by cutting the sealing portion in between the packages,
and are then transferred to a final folding station where they are folded mechanically
into the final shape.
[0006] EP-B-O 091 712 illustrates and describes a forming and sealing unit of the above
type, in which the reciprocating movement of the jaws is controlled by a cam system.
That is, the system comprises an electric motor, the output shaft of which is fitted,
for each pair of jaws, with two cams with appropriately differing profiles. By means
of respective rocker arms, the cams control the axial reciprocating movement of respective
vertical rods, one of which is connected to a slide supporting the jaws and to which
the jaws are hinged; while the other rod extends through the slide, without being
connected functionally to it, and controls, by means of articulated arms, the reciprocating
opening and closing movement of the jaws.
[0007] Two mutually facing forming flaps are hinged to respective jaws in each pair, and
are movable between an open position, into which they are pushed by elastic means,
and a closed position in which they mate to define a space defining the form and volume
of the package to be formed. The forming flaps are closed by cams fixed to the machine
frame and which interact with respective rollers carried by the flaps. The specific
configuration of the forming flaps is described, for example, in EP-B-O 460 540.
[0008] At the same time, the tube portion compressed between the jaws is sealed transversely
by heating means, e.g. induction or ultrasonic, carried by the jaws; and, once sealing
is complete, a cutter is activated to cut the tube of packaging material along the
center of the sealed portion and so detach a pillow package from the bottom end of
the tube. As the bottom end is sealed transversely, the jaws, on reaching the bottom
dead center position, may be opened to prevent interfering with an upper portion of
the tube. At the same time, another pair of jaws, operated in the same way, moves
down from the top dead center position, and the above gripping/forming, sealing and
cutting operations are repeated.
[0009] Though highly successful and reliable, even to the extent of requiring very little
maintenance even after many years' service, machines of the above type have several
drawbacks, particularly as regards adaptability to production changes and the limited
extent to which the position of the designs may be corrected, as explained below.
[0010] Machines of the above type do in fact cater for producing packages of various shapes
and sizes, but only at the expense of substantially reconstructing some parts of the
machine and replacing many others, thus resulting in considerable cost and downtime.
[0011] EP-A-O 140 280 describes a device for producing packages containing a pourable food
product, wherein the vertical travel of the slides is controlled, via a rocker arm,
by a pulse motor for adjusting the amount of travel. This solution provides for a
certain amount of adjustment of the device to produce packages of different heights,
but of the same cross section, so that any change in the configuration of the package
also involves substantial alterations to the machine.
[0012] To minimize downtime of the machine, a demand therefore exists in this particular
field for a forming and sealing unit which provides not only for rapidly adjusting
the height of the package, but also for adjusting the configuration of the package
as required, to switch, for example, from a package of a given width and depth to
one of greater or lesser width and/or depth, or from a square-cornered to a beveled-cornered
package in the shortest time possible.
[0013] Another technical drawback of known forming and sealing units lies in the so-called
"design correction" system.
[0014] As the web of packaging material normally comprises a series of equally spaced printed
images or designs on the portions eventually defining the outer surfaces of the packages,
the web must be so supplied to the forming and sealing unit that the package forming,
sealing and cutting operations are "registered" accurately with respect to the succession
of designs. In actual use, however, despite the designs being equally spaced, the
position of each design with respect to the jaws on the forming and sealing unit may
vary due to varying deformation of the packaging material by the mechanical pressure
exerted by the jaws, or due to the pulsating pressure of the pourable food product
inside the tube of packaging material, so that a device is required to correct the
position of the designs.
[0015] On modern packaging machines, such a device comprises an optical sensor for detecting
the position of a bar code on the package; and a control unit for comparing the detected
position with a theoretical position.
[0016] Each pair of jaws is provided with a pair of drawing members for pulling the tube
of packaging material, and which are movable with respect to the jaws to form triangular
flaps at the top and bottom corners of the pillow package. On detecting a design position
error, the control unit adjusts the speed of the motor supplying the web of packaging
material, and, if this correction is not enough, the drawing members are also controlled
to slightly increase or reduce the pull exerted on the packaging material. The above
operation is repeated until the position of the design matches the theoretical position,
in which case, any packages produced in the meantime must be rejected. At times, even
this method fails to ensure correct positioning of the designs, as, for example, when
replacing the roll of packaging material with one in which the design pitch is different.
In which case, the machine must be stopped and reset manually to the design pitch
of the new roll.
[0017] A further object of the present invention, therefore, is to provide a forming and
sealing unit enabling fast effective correction to minimize the number of rejects
and eliminate the downtime involved in resetting the machine manually.
[0018] According to the present invention, the aforesaid objects are achieved by a forming
and sealing unit as claimed in Claim 1.
[0019] A preferred, non-limiting embodiment of the present invention will be described by
way of example with reference to the accompanying drawings, in which:
Figures 1 and 2 show a side and front view respectively of a forming and sealing unit
for a machine for packaging pourable food products, in accordance with the teachings
of the present invention;
Figure 3 shows a larger-scale partial side view of the Figure 1 and 2 unit in a different
operating condition;
Figure 4 shows a view in perspective of an actuating assembly of the unit;
Figure 5 shows an exploded view in perspective of a transmission unit of the Figure
4 assembly;
Figures 6 and 7 show a front and side view respectively of a detail of the Figure
5 transmission unit.
[0020] Number 1 in Figures 1 and 2 indicates as a whole a forming and sealing unit for a
machine (not shown) for packaging pourable food products, such as pasteurized or UHT
milk, fruit juice, wine, etc..
[0021] Unit 1, in particular, provides for producing aseptic sealed packages, containing
a pourable food product, from a tube 2 of packaging material formed by folding and
longitudinally sealing a web of heat-seal sheet material, and filled with the food
product upstream from unit 1.
[0022] Tube 2 is fed to unit 1 in known manner along a vertical path defined by an axis
A.
[0023] Unit 1 comprises a supporting structure 3 defining a pair of vertical guides 4 located
symmetrically with respect to the longitudinal vertical mid plane α of the unit through
axis A.
[0024] Unit 1 comprises, in known manner, a pair of forming assemblies 5, 5' movable vertically
along respective guides 4, and which interact alternately with tube 2 of packaging
material to grip and heat seal cross sections of the tube.
[0025] As assemblies 5, 5' are known and symmetrical with respect to plane α, only one (assembly
5) will be described herein, and only as regards the parts pertinent to the present
invention, using the same reference numbers for the corresponding parts of both assemblies
5, 5'.
[0026] Assembly 5 substantially comprises a slide 6 which runs along respective guide 4;
and a pair of jaws 7 substantially in the form of appropriately ribbed quadrangular
plates, and which are hinged to the slide at the bottom about respective horizontal
axes 8a, 8b perpendicular to plane α, and have respective control brackets 9 projecting
from respective opposite faces.
[0027] Jaws 7 are fitted integrally with respective supporting arms 10, which are fixed
to the top ends of respective jaws 7 and project towards and beyond plane α so as
to be positioned on either side of tube 2 (Figure 2).
[0028] The projecting portions of arms 10 are fitted with respective bar-shaped sealing
elements (not shown) for interacting with tube 2. Which elements may be defined, for
example, by an inductor for generating current in the aluminium layer of the packaging
material and melting the thermoplastic layer by virtue of the Joule effect; and by
a contrast pad enabling the necessary gripping pressure to be applied to the tube.
[0029] The movement of jaws 7 is controlled in known manner by a pair of vertical rods 15,
16.
[0030] Rod 15 is connected rigidly to slide 6 and therefore controls the vertical movement
of assembly 5; while rod 16 extends through, without being connected to, slide 6,
and is connected at the bottom end 17 to the control brackets 9 of jaws 7 by means
of respective connecting rods 18, so that the downward movement of rod 16 with respect
to rod 15 opens jaws 7 (Figure 3).
[0031] Jaws 7 are movable between a closed position (shown in Figure 3 relative to assembly
5') and a fully-open position (shown in Figure 3 relative to assembly 5). As this
movement is superimposed on the vertical reciprocating movement of slides 6, rods
15 move reciprocatingly, while rods 16 perform a periodic axial movement defined by
a combination of the reciprocating movement of rods 15 and a further periodic movement
for opening and closing jaws 7. Respective known forming flaps 19 are also hinged
to arms 10.
[0032] According to the present invention, rods 15, 16 of each forming assembly 5, 5' are
controlled independently by respective servomotors 20, 21, 20', 21' (Figure 4).
[0033] All four servomotors 20, 21, 20', 21' are housed in side by side pairs at the top
of structure 3. More specifically, motors 20, 21 of assembly 5 are mounted on one
side of structure 3, and have respective output shafts (not shown) facing and coaxial
with each other, with the respective axes parallel to plane α; and servomotors 20',
21' of assembly 5' are mounted in the same way on the other side of structure 3 and
symmetrically with servomotors 20, 21 with respect to plane α.
[0034] Each servomotor 20, 21, 20', 21' is conveniently fitted to a supporting frame 22,
which is connected to a respective bracket 24, projecting laterally from structure
3, by means of a respective vertical hinge 23. This provides for troublefree access
to servomotors 20, 21, 20', 21' for maintenance purposes, by enabling each to be substantially
"extracted", without being dismantled completely, from structure 3 by rotating it
outwards about respective hinge 23.
[0035] Each pair of motors is provided with a respective transmission unit 25, 25'. As both
units are identical and located symmetrically with respect to plane α, only unit 25,
shown in detail in Figure 5, will be described, the same considerations obviously
also applying, mutatis mutandis, to unit 25'.
[0036] Transmission unit 25 comprises a supporting frame 27, in turn comprising an annular
base flange 28 fitted to supporting structure 3 of unit 1, over motors 20, 21, and
a gantry structure 29 extending upwards from flange 28.
[0037] Frame 27 houses and supports two belt transmissions 33a, 33b interposed respectively
between motor 20 and respective rod 15, and between motor 21 and respective rod 16.
As transmissions 33a, 33b are substantially identical, only transmission 33a will
be described, the elements of transmission 33b being indicated using the same reference
numbers as for the corresponding elements of transmission 33a.
[0038] Transmission 33a comprises a toothed belt 34, which meshes with a drive pulley 35
fitted to the output shaft of motor 20, and with a transmission pulley 36 fitted idly
to a supporting fork 37 connected to a top cross member 38 of gantry structure 29
by means of a tensioning device 39 shown in Figures 6 and 7 and described in detail
later on. The axes of pulleys 35 and 36 lie in a vertical plane parallel to plane
α, so that belt 34 comprises a pair of vertical parallel branches.
[0039] One of said branches of the belt is fitted rigidly with a shoe or runner block 42
defined by a slide element 43 inwards of the belt and meshing with the toothing, and
by a fastening element 44 outwards of the belt and connected rigidly to element 43
to sandwich the belt.
[0040] Element 43 cooperates in sliding manner with a vertical guide section 55 carried
integrally by a supporting frame 56 fixed rigidly inside frame 27.
[0041] Element 44 comprises a fastening portion 45 to which is connected the top end of
rod 15.
[0042] With reference to Figures 6 and 7, tensioning device 39 comprises a tubular body
46, which is fitted to the top cross member 38 of gantry structure 29 of frame 27,
through an opening 47 in the cross member (Figure 5).
[0043] Device 39 also comprises a vertical shaft 48 fitted through and sliding axially with
respect to tubular body 46; and a fastening portion 49 is formed at the bottom end
of shaft 48 and connected rigidly to fork 37.
[0044] A coil spring 50, coaxial with shaft 48, is compressed axially between tubular body
46 and a stop ring 51 fitted rigidly to and close to the top end of shaft 48, so as
to push shaft 48 and, hence, fork 37 elastically upwards.
[0045] Tensioning device 39 also comprises a pair of cylindrical bushes 52 located diametrically
opposite each other with respect to body 46, with their respective axes extending
radially with respect to the axis of body 46 and lying along a common straight line
C.
[0046] Bushes 52 are fitted in rotary manner to respective pins (not shown), and house respective
springs (not shown) for torquing the bushes in opposite directions (e.g. clockwise,
with reference to the bush 52 shown in Figure 6). Advantageously, bushes 52 are mounted
on non-return needle bearings for uni-directional rotational movement.
[0047] Each bush 52 carries an integral cam 54 extending circumferentially along a fraction
of the lateral surface of bush 52; and each cam 54 has a lift profile increasing in
the opposite direction to the torque acting on the bush.
[0048] Stop ring 51 comprises a pair of diametrically opposite arms 57, each projecting
towards a respective bush 52; and, at the free end, each arm 57 defines a respective
internally threaded bush 58 in which is screwed a respective adjustment or setting
screw 59 cooperating at the end with respective cam 54.
[0049] Servomotors 20, 21, 20', 21' are connected to a control unit 60, which may be programmed
to vary the parameters governing operation of the motors, and therefore to vary the
operating cycles of unit 1.
[0050] Unit 1 operates as follows.
[0051] The vertical movement of rods 15, 16 controlling forming assemblies 5, 5' is controlled
by servomotors 20, 21, 20', 21'. Rotation of the output shaft 33 of each servomotor
is transmitted, via respective drive pulley 35, to toothed belt 34, which produces
a vertical movement of respective shoe or runner block 42 and hence respective rod
15, 16.
[0052] Servomotors 20, 21, 20', 21' are controlled to govern the movement of rods 15, 16
of forming assemblies 5, 5' as required to perform the operating cycle of unit 1.
[0053] Very briefly, jaws 7 of each assembly 5, 5' close during the downward travel of the
assembly, so as to grip tube 2 with a vertical downward component of motion equal
to the traveling speed of tube 2. Jaws 7 remain closed during the downward travel,
and the sealing elements grip the tube with sufficient pressure to heat seal it. Close
to the bottom dead center position, jaws 7 open to release tube 2, are opened further
during the upward travel, and reach the fully-open position (Figure 3) prior to reaching
the top dead center position. The jaws then start closing, and are closed completely
after reaching the top dead center position for the reasons explained above.
[0054] Operation of assemblies 5 and 5' is obviously offset by half a cycle : assembly 5
moves up with jaws 7 open as assembly 5' moves down with the jaws closed, so that
arms 10 of assembly 5' pass between the arms of assembly 5 without interfering therewith.
[0055] Tensioning devices 39 ensure correct tension - defined by the elastic load of springs
50 - of belts 34, even in the event of the belts stretching. In which case, shaft
48 is pushed upwards by spring 50 to form a clearance between screws 59 and cams 54;
which clearance, however, is taken up automatically by bushes 52 rotating and so bringing
a higher lift portion of cams 54 into contact with the screws. Devices 39 therefore
permit upward movement of respective transmission pulleys 36 to compensate for the
stretching of belts 34, but prevent any movement in the opposite direction.
[0056] Control of assemblies 5, 5' by servomotors 20, 21, 20', 21' enables the operating
cycle parameters (travel, speed) to be adjusted as required according to the volume
and configuration of the packages to be produced, with no major mechanical alterations
to the machine. Moreover, as forming assemblies 5, 5' are controllable independently,
the position of the designs on the packages may be corrected rapidly and easily, thus
reducing the number of rejects.
[0057] More specifically, in the presence of an input signal indicating a position error
of the design with respect to the theoretical position, the traveling speed of one
of assemblies 5, 5' may be varied with respect to the other within one cycle, with
no change in the relative start- and end-of-cycle position. And once the required
correction is achieved, the control unit may so control speed as to restore the relative
position of forming assemblies 5, 5' before the end of the cycle.
[0058] Further advantages of unit 1 according to the present invention are greater compactness
and lower cost as compared with conventional mechanically cam-controlled units.
[0059] Clearly, changes may be made to the unit as described and illustrated herein without,
however, departing from the scope of the accompanying Claims.
1. A forming and sealing unit (1) for producing aseptic sealed packages, containing a
pourable food product, from a tube (2) of packaging material filled with said food
product and fed along a vertical path (A), said unit (1) comprising a fixed structure
(3); a pair of forming assemblies (5, 5') interacting alternately and cyclically with
said tube (2) of packaging material, and in turn comprising respective slides (6)
movable vertically and in reciprocating manner with respect to said fixed structure
(3), and respective pairs of jaws (7) having sealing means and movable between an
open position and a closed position in which said sealing means cooperate with said
tube (2) of packaging material; a first pair of control members (15) for controlling
the movement of said slides (6); a second pair of control members (16) for controlling
the opening and closing movement of said jaws (7); and activating means for activating
said first and second control members (15, 16); characterized in that said activating
means comprise independently adjustable actuating means (20, 21, 20', 21') for each
said control element (15, 16).
2. A unit as claimed in Claim 1, characterized in that said actuating means comprise
a servomotor (20, 21, 20', 21') for each said control element (15, 16).
3. A unit as claimed in Claim 2, characterized by comprising a control unit (60) connected
to said servomotors (20, 21, 20', 21') and which is programmable to vary the movement
of said control members (15, 16).
4. A unit as claimed in Claim 2 or 3, characterized in that said first control members
comprise a pair of vertical first rods (15) connected to the respective said slides
(6); and said second control members comprise a pair of vertical second rods (16)
connected to the respective said pairs of jaws (7); said unit (1) comprising belt
transmission means (33a, 33b) interposed between each servomotor (20, 21, 20', 21')
and the respective said rod (15, 16).
5. A unit as claimed in Claim 4, characterized in that said belt transmission means (33a,
33b) comprise a toothed belt (34) activated by the servomotor (20, 21, 20', 21') and
having at least one portion movable along a vertical plane; and a shoe (42) connected
rigidly to said portion of said belt (34) and having connecting means (45) for connection
to a said respective rod (15, 16).
6. A unit as claimed in Claim 5, characterized in that said transmission means (33a,
33b) comprise tensioning means (36, 37, 46, 48, 50, 51) for each said belt (34).
7. A unit as claimed in Claim 6, characterized in that said tensioning means comprise
a transmission pulley (36) cooperating with said belt (34); supporting means (37,
48, 51) for supporting said transmission pulley (36); fastening means (46) for fastening
said supporting means (37, 48, 51) to said fixed structure (3) of said unit (1); and
elastic means (50) interposed between said supporting means (37, 48, 51) of said transmission
pulley (36) and said fastening means (46), to exert on said supporting means (37,
48, 51) a force for tensioning said belt (34).
8. A unit as claimed in Claim 7, characterized in that said tensioning means comprise
one-way retaining means (54, 59) interposed between said supporting means (37, 48,
51) of said transmission pulley (36) and said fastening means (46), and which permit
movement of said supporting means (37, 48, 51) of said transmission pulley (36) with
respect to said fastening means (46) in the determined stretch direction of said belt
(34), and prevent relative movement in the opposite direction.
9. A unit as claimed in Claim 8, characterized in that said one-way retaining means comprise
cam means (54) carried by said fastening means (46); and pressure means (59) carried
by said supporting means (37, 48, 51) of said pulley (36); said cam means (54) having
a variable lift profile, and being pushed elastically to recover any clearance formed
between said cam means (54) and said pressure means (59).
10. A unit as claimed in Claim 9, characterized in that said supporting means of said
pulley (36) comprise a supporting fork (37); a shaft (48) connected rigidly to said
fork (37); and a stop element (51) fitted rigidly to said shaft (48); said fastening
means comprising a tubular body (46) fitted to said fixed structure (3) and housing
said shaft (48) in sliding manner; and said elastic means comprising a spring (50)
compressed between said tubular body (46) and said stop element (51).
11. A unit as claimed in Claim 10, characterized in that said cam means comprise at least
one cam (54) rotating about an axis (C) extending radially with respect to said tubular
body (46); and in that said pressure means comprise a pressure screw (59) cooperating
with said cam (54) and carried by an arm (57) integral with said stop element (51);
said cam (54) being charged by said elastic means (50) to bring increasing-lift portions
of said profile into contact with said screw (59) in the event of a clearance forming
between said cam (54) and said screw (59).
12. A unit as claimed in one of the foregoing Claims from 2 to 11, characterized in that
said servomotors (20, 21, 20', 21') are fitted to respective supporting elements (22)
so as to be at least partly withdrawable from said structure (3) of said unit (1).
13. A unit as claimed in Claim 12, characterized in that said supporting elements (22)
are hinged to said structure (3) of said unit (1).