[0001] The present invention relates to systems for handling particulate materials, e.g.
foodstuffs.
[0002] In one aspect the invention relates to a conduit having an inlet and an outlet, the
outlet being of smaller cross-sectional area than the inlet. Generally the inlet is
intended to be higher than the outlet, and the conduit is arranged so that particulate
material can fall from the inlet to the outlet . The inlet may be intended to receive
weighed batches or charges of particulate material from a weighing unit. The outlet
may be intended to be coupled to a downstream processing station, having an inlet
of similar dimensions to the conduit's outlet. The processing station may be a packaging
station, e.g. comprising a bag making machine.
[0003] In another aspect the invention relates to a packaging assembly having a first station
(e.g. a weighing station) for providing batches of particulate product and a second
station for treating (e.g. packaging) batches. The second station has an inlet smaller
than the outlet of the first station and they are coupled via a conduit which embodies
the first aspect.
[0004] It is a known problem of existing systems in which particulate material has to be
fed through a relatively narrow orifice that blockages occur.
[0005] It is a known problem of existing systems in which batches of particulate material
are fed discretely along a conduit that the batches tend to spread out excessively
and cease to be separate from adjacent batches.
[0006] Preferred embodiments of the invention may enable one to ameliorate or solve either
or both of these problems.
[0007] According to the invention, a conduit has a tapering portion of noncircular internal
cross-section for discouraging helical flow along it. It is preferably of facetted
cross-section. The noncircular conduit portion is preferably offset, in that its outlet
is at a lower level than its inlet, and laterally spaced from it. It may communicate
with a second tapering portion. This may have internal walls that are generally steeper
than those of the first tapering portion. It may have one or more transitions at which
the wall steepness increases. Upper and lower portions of the second tapering portion
may both extend substantially vertically, with one being laterally offset with respect
to the other. The upper portion may have one or more internal fins extending downwardly
to restrain swirling.
[0008] The conduit, or at least the second tapering portion, may be mounted so as to be
vibratable and coupled to a vibratory device.
[0009] A preferred type of embodiment works on the principle of keeping the charge going,
letting the speed build up as the charge drops through the system, but limiting the
amount the charge spreads out (or disseminates). This means that the charge enters
into the smallest diameter at a high speed and the particles making up the charge
are spread out to an extent so that the density of the charge at this point is low.
Therefore the chances of a jam are very low. This combined with the shape of the outlet
chute and with the use of vibration lower the chance of jamming to nearly zero. Because
the charge is travelling fast, even with the spread there will be a clear gap between
the charges. This allows for the down line processing such as bag making or carton
filling.
[0010] An embodiment of the invention will now be described by way of example with reference
to the accompanying drawings in which:
Fig. 1 is a vertical section through an embodiment of the invention and;
Fig. 2 is an enlarged view of the outlet chute shown in Fig. 1.
[0011] Fig. 1 shows part of a weighing station 10, which may be generally conventional.
It has one or more outlets 12, each having an outlet port 14 of relatively large cross-sectional
area. Spaced below the weighing unit 10, there is a respective bag-making machine
16 associated with each outlet 12. In Fig. 1, only one is shown. It has an upper mouth
18 which is of much smaller cross-sectional area than the outlet port 14 of the weighing
machine 10. The two are coupled together by means of a conduit assembly 20.
[0012] The conduit assembly 20 has an upper chute portion 22. This is an angled, tapering
tube, of facetted cross-section. The illustrated example is octagonal in section.
Its upper opening 24 is of very similar cross-sectional area to the outlet port 14
of the weighing machine. Being octagonal, it cannot match it exactly, so it is very
slightly larger so that no particulate material emerging through the port 14 can fall
outside the chute 22.
[0013] The chute extends steeply downwardly and slightly laterally to its outlet end where
it is coupled to an outlet chute 26. This may be of generally circular cross-section
and may extend substantially vertically. It is shown in more detail in Fig. 2.
[0014] Its upper mouth 28 is very slightly larger than the outlet aperture 30 of the upper
chute 22. The upper section 32 of the outlet chute 26 tapers slightly, to an annular
vertex region 34. Below this, in the outlet portion of the outlet chute, the internal
wall is closer to the vertical. It is still tapered. The tapering has an asymmetry,
such that the outlet 36 is slightly off-centred with respect to the upper inlet 28.
Thus as shown in Fig. 2, at one side 38 the wall has a continuous taper whereas at
the other side 40, the tapering ends at a vertex 44 and the final portion of the internal
wall 46 extends vertically (that is, parallel to the axis), with the result that the
centre line 48 of the exit aperture 36 is slightly off set from the centre line 50
of the inlet aperture 30. The lower portion of the outlet chute is smoothly shaped
so that, circumferentially, there is a smooth transition from the vertical portion
46 to the angle of taper at the diametrically opposite portion. The offsetting is
achieved without any internal step that would interfere with particle flow.
[0015] In use, the weighing machine 10 accumulates successive batches or charges of particulate
material, and releases them at intervals, into the top of the conduit 20. Each charge
drops in through the mouth 24 without any retardation. The facetted chute is quite
steep, despite the offsetting, so the material can pass through quickly. When particulate
material falls through a simple tubular conduit, particles tend to diverge from a
direct path, parallel to the axis. There is a tendency to adopt helical paths. Much
kinetic energy tends to be lost when this occurs, resulting in some particles travelling
through the conduit much slower than the rest. The batch or charge of material thus
becomes spread out.
[0016] However, with the facetted chute, the particles are kept moving substantially in
the intended, downstream direction. If they start to deviate and move across the chute,
the facets interrupt this component of their motion.
[0017] The outlet chute 26 has very steep sides, to keep the particles moving smoothly,
with minimum contact. The final portion is offset. This produces an angular transition,
which eases the passage from the larger to the smaller diameter, corresponding to
the inlet diameter of the packaging machine 16.
[0018] Because of the design of the conduit, the charge of material does not spread out
substantially during transit and it passes through the exit orifice at high speed.
The overall length of the conduit is such that there will have been some spreading
out in the direction of travel. Some spreading is actually desirable, since it reduces
the density of the material and thus reduces the chance of a jam. Because the charge
is travelling fast, even with the spreading that does occur, there will be a clear
gap between successive charges. This facilitates downstream processing such as bag-making
or carton filling.
1. A conduit for conveying particulate material from an inlet to an outlet which is lower
than the inlet and of smaller cross-sectional area, wherein said conduit has a tapering
portion of noncircular internal cross-section for discouraging helical flow along
it, said noncircular conduit portion having an offset, such that its outlet is at
a lower level than its inlet, and laterally spaced from it.
2. A conduit according to claim 1 wherein said noncircular conduit portion is facetted.
3. A conduit according to claim 1 or claim 2 in which said noncircular conduit portion
communicates with a second tapering portion which has internal walls that are generally
steeper than those of the first tapering portion.
4. A conduit according to claim 3 wherein said second tapering portion has one or more
transitions at which the wall steepness increases.
5. A conduit according to claim 4 wherein upper and lower portions of the second tapering
portion both extend substantially vertically, with one being laterally offset with
respect to the other.
6. A conduit according to claim 5 wherein said upper portion of the second tapering portion
has one or more internal fins extending downwardly to restrain swirling.
7. A conduit assembly including a conduit according to any preceding claim wherein the
conduit or, if present, at least the second tapering portion, is mounted so as to
be vibratable and is coupled to a vibratory device.
8. A packaging assembly having a first station for providing batches of particulate product
and a second station for treating batches, wherein the second station has an inlet
smaller than the outlet of the first station and they are coupled via a conduit or
conduit assembly according to any preceding claim.
9. A method of conveying a batch of particulate material from a first orifice to a second
orifice of smaller cross-sectional area comprising coupling said orifices by means
of a conduit according to any of claims 1-6 or an assembly according to claim 7 and
discharging the batch through the first orifice into the conduit.