TECHNICAL FIELD The present invention relates to a machine for filling containers, such as parallelepiped-shaped boxes of cardboard or similar, with an incoherent fill material, such as powder or similar particulate material.

More specifically, the present invention relates to a machine for filling containers with incoherent fill material, of the type comprising a conveying wheel; a succession of weighing devices connected to the conveying wheel, each weighing device supporting and retaining a respective container, and the conveying wheel rotating about a respective axis to feed the containers along a path comprising a given filling portion; and a filling unit located over the conveying wheel, rotating with the conveying wheel, and comprising a hopper chamber for receiving the fill material; the hopper chamber having a number of outflow openings for feeding the fill material into the containers.

BACKGROUND ART In known filling machines of the type described above, in which the fill material is fed gradually into the containers as the containers travel along the fill path and until a given weight is reached, and wherein the weight of the fill material fed into each container is determined continuously by the relative weighing device

along the whole length of the fill path, smooth flow, even of minimum amounts, of the fill material through the outflow openings must be assured at all times. This, however, is not always achieved, on account of the incoherent material-especially fine particulate material fed in large amounts into the hopper chamber, normally a cylindrical hopper-becoming packed under its own weight at the bottom of the hopper, thus clogging the outflow openings.

DISCLOSURE OF INVENTION It is an object of the present invention to provide a machine for filling containers with incoherent fill material, designed to eliminate the aforementioned drawbacks.

According to the present invention, there is provided a machine for filling containers with incoherent fill material, as claimed in Claim 1 and, preferably, in any one of the following Claims depending directly or indirectly on Claim 1.

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 schematic plan view, with parts removed for clarity, of a bottom portion of a preferred embodiment of the filling machine according to the present invention; Figure 2 shows a schematic diametrical section of a

top portion of the Figure 1 filling machine; Figure 3 shows a larger-scale view of a detail in Figure 2.

BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figure 1 indicates as a whole a filling machine for filling, with a given incoherent fill material, containers 2 defined by open-topped, substantially parallelepiped-shaped cardboard boxes or similar.

Machine 1 comprises a conveyor 3, in turn comprising two wheels 4 and 5 fitted to a frame 6 to rotate, with respect to frame 6, about respective axes 7 and 8 perpendicular to the Figure 1 plane, and a conveying member 9 looped about wheels 4 and 5, and having a succession of pockets 10, each for receiving and retaining a respective container 2. Machine 1 also comprises a filling unit 11 (Figure 2) located over wheel 5, and for filling containers 2 to a given weight.

Conveying member 9 feeds containers 2, housed inside pockets 10, along a path P which comprises a curved filling portion P1 extending about part of wheel 5 and beneath filling unit 11; a loading portion P2 extending from a loading station 12 where empty containers 2 are loaded onto conveying member 9; and an unloading portion P3 located on the opposite side of filling portion P1 to loading portion P2, and which terminates at an unloading station 13 where the full containers 2 are unloaded off conveying member 9.

Wheel 5 is larger in diameter than, and preferably at least twice the diameter of, wheel 4; filling portion P1 extends along an arc of about 270° about the periphery of wheel 5; and loading portion P2 and unloading portion P3 are straight parallel portions which are tangent to wheel 4, are separated by a distance substantially equal to the diameter of wheel 4, and are connected to the respective ends of filling portion P1 by respective bends 14 and 15.

As shown in Figure 2, wheel 5 comprises a cylindrical base body 16 coaxial with axis 8 and fitted to a drive shaft 17 fitted in rotary manner to frame 6.

An annular body 19, coaxial with axis 8, is fitted to the top of cylindrical body 16 by means of studs 18, and has, on its outer periphery, two superimposed ring gears 20 for respective chains 21 forming part of conveying member 9 and supporting pockets 10. Each pocket 10 is substantially U-shaped, and comprises an intermediate wall 22 parallel to axis 8, located outside chains 21, and connected to chains 21 by a bracket 23; and two lateral walls 24 connected to the relative lateral edges of intermediate wall 22 by respective hinges enabling relative lateral walls 24 to oscillate, under the control of a known actuating device (not shown) and about respective axes parallel to axis 8, to and from a closed position in which lateral walls 24 are parallel to each other to grip and retain between them a relative container 2.

As shown in Figure 2, wheel 5 comprises a number of weighing devices 25 which are equally spaced about cylindrical body 16 with the same spacing as pockets 10 along conveying member 9, and are synchronized with pockets 10 along filling portion P1.

As shown more clearly in Figure 2, each weighing device 25 comprises a box body 26 fitted to a bottom surface of cylindrical body 16 to project radially outwards of cylindrical body 16, and housing a scale (not shown) supporting a respective pocket 27, which rotates with wheel 5 about axis 8 and in time with a respective pocket 10, and comprises a base plate 28 for supporting a respective container 2, and a gripper 29 for laterally engaging respective container 2, and which is movable between a closed position gripping relative container 2, and an open position releasing container 2.

With reference to Figure 2, filling unit 11 comprises a dispensing member 30 mounted over and coaxial with wheel 5, and rotating with wheel 5 about axis 8.

Dispensing member 30 comprises a powered telescopic upright 31 extending upwards from wheel 5 and smaller in outside diameter than annular body 19 ; and a head 32 integral with the top end of upright 31. Head 32 comprises a top portion 33 having a conical, upward- tapering lateral surface 34 coaxial with axis 8 and having a base 34a; and a bottom portion 35 having a cylindrical lateral wall 36 of the same diameter as base 34a and bounded at the bottom by a flat annular wall 37,

which is perpendicular to axis 8 and has a peripheral annular portion 38 projecting outwards of lateral wall 36 and having a number of outflow openings 39, each located directly over a respective plate 28.

Filling unit 11 also comprises a substantially cylindrical casing 40 coaxial with wheel 5 and surrounding head 32 to define, with head 32, an annular hopper chamber 41 communicating with the outside through a central hole 42, through which is inserted a feed conduit 43, a bottom edge of which is located close to lateral surface 34 of head 32 to define, with lateral surface 34, an annular gap 44 coaxial with axis 8 and through which the incoherent material with which to fill containers 2 is fed into hopper chamber 41. Casing 40 has an inside diameter larger than the outside diameter of lateral wall 36 of bottom portion 35 of head 32, and rests on and is welded to an outer edge of peripheral annular portion 38 of wall 37 to define, with annular portion 38 and lateral wall 36, an annular channel 45 communicating with the outside through outflow openings 39.

As shown more clearly in Figure 3, each outflow opening 39 defines a seat for a relative removable insert 46 having a normally substantially oval-section through hole 47, the size of which depends on the size of containers 2 to be filled, and the outlet of which is adjustable by means of a respective valve device 48. Each valve device 48 is supported by an annular plate 49 which

is fitted integrally to the underside of wall 37, is coaxial with axis 8, projects outwards of casing 40, and has through openings 50, each of which coincides partly with a respective outflow opening 39 and is engaged by a respective insert 46.

Each valve device 48 comprises two opposite actuators 51 which are fitted to annular plate 49 in radially coaxial positions, are controlled by the scale (not shown) of relative weighing device 25, and activate respective shutters 52 movable to and from a position contacting each other to fully close relative hole 47.

As shown in Figure 2, filling unit 11 also comprises a known stirring device 53 which is secured in a fixed position to feed conduit 43, and comprises a sloping arm 54 extending inside hopper chamber 41 along conical lateral surface 34 of top portion 33 of head 32, and fitted on its free end with a powered blade 55 engaging channel 45 and rotating about an axis 56 perpendicular to axis 8.

In actual use, containers 2, in the form of flat tubular packages 57, are withdrawn successively in known manner from a stack 58 by a gripper drum 59, and are fed into respective pockets 10 at loading station 12. As it is fed into relative pocket 10, each flat tubular package 57 is"unfolded"in known to form a hollow tubular package and, as it travels along loading portion P2 and through a known folding station 60, is closed at the bottom to form an open-topped, cup-shaped container 2

having upward-facing flaps 61 at the top end.

As it is fed along loading portion P2, each container 2 is engaged laterally by lateral walls 24 of relative pocket 10 in the closed position, and is so retained contacting intermediate wall 22 of relative pocket 10 which, as it travels along bend 14, gradually mates with a relative pocket 27 which receives relative pocket 10 with gripper 29 in the open position. At the start of filling portion P1, gripper 29 is closed onto container 2 without interfering with lateral walls 24 which, immediately after, are moved into the open position to release container 2 inside relative pocket 27, resting on relative plate 28, and gripped between the jaws of relative gripper 29.

In the position described above, container 2 therefore no longer interferes in any way with relative pocket 10 which accompanies it along the whole length of filling portion P1, and the weight of container 2 rests entirely, and with no outside interference, on relative weighing device 25.

Each container 2 is filled gradually to the desired weight as container 2 travels along filling portion P1, and by feeding a continuous, controlled stream of fill material through relative hole 47, the distance of which from relative plate 28 has been adjusted beforehand by adjusting the length of upright 31 to the height of container 2 to be filled.

Continuous flow of the fill material through holes

47, as relative valve devices 48 are opened, is ensured not only by stirring device 53, which prevents the fill material inside channel 45 from forming"bridges", but also, and above all, by reducing compaction of the fill material inside channel 45. More specifically, the fill material issuing from feed conduit 43 through annular gap 44-the outlet of which is maintained at a substantially constant predetermined value by adjusting the position of feed conduit 43 as a function of the axial position of head 32 on wheel 5-flows along and forms on lateral surface 34 a layer whose weight is substantially supported by head 32 by virtue of the relatively wide flare angle (about 110-130°) of conical lateral surface 34. As a result, the weight of the material flowing along conical lateral surface 34 is supported by head 32, as opposed to weighing on the material inside channel 45.

With reference to one container 2, as container 2 enters filling portion P1, the relative formerly closed valve device 48 opens to allow the fill material inside channel 45 to drop through relative hole 47. Each weighing device 25 normally controls relative valve device 48 so that the flow of material through relative hole 47 is fairly considerable to begin with, and is gradually reduced to zero as the continuously monitored weight of the fill material fed into relative container 2 nears the desired weight, which is normally reached close to the end of filling portion P1.

When container 2 reaches bend 15, lateral walls 24

of relative pocket 10 close to grip container 2 laterally, and relative gripper 29 opens to release container 2 onto conveying member 9, which feeds container 2 through a folding station 62 where flaps 61 are folded and connected in known manner to close container 2. Conveying member 9 then feeds container 2 through a known reject station 63 and to unloading station 13 where, after opening lateral walls 24 of relative pocket 10, the full container 2 is unloaded in known manner off conveying member 9 and onto an output conveyor 64.