Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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TITLE: VIBRATORY DISTRIBVTION SYSTEM
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The present invention relates to a distribution system
f or f lowable materials.
Distribution systems are used, inter alia, for conveying
bulk food products such as crisps, cornflakes and similar
products of relatively low mass and irregular shape from
-- a source such as an oven to a number of processing points
at which the product is, for example, packaged by
packing machines which dispense metered quantities of
th~ product to successively presented packages or
containers.
One of the problems associated with such distribution
systems is ensuring that the supply of food products is
suff`icien to meet the demand at all ~f the processing
points since failure to do so can result in product
starvation at the processing points and consequent
production of underweight packages. One known form of
distribution system attempts to solve this problsm by
conveying the food product in a closed path along which
the various processing points are located. Product
which is not immediately used continues to be conveyed
along the closed path until eventually required. A
disadvantage of this system is that food products such
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as crisps and cornflakes are quite fragile and the longer
the products spend in the distribution system the more
likelihood there is of the packaged product containin~
an unacceptably high level of broken or powdered product.
In addition, the products also tend to degrade if left
exposed to the air for any appreciable time.
In a further known system quantities of product are
amassed at each processing point and dropped through an
opened gate into a storage hopper of a packaging machine
at the processing point. A disadvantage of this system is
that the sudden discharging of a large quantity of
product into the packaging machine hopper can effect the
accuracy of the machine and result in large variations
in the quantity of product metered to each package. Since
such machines have to be set to ensure that the metered
quantity of product does not fall below the quantity
specified on the package the metered quantity can be
as much as 50~ greater than the specified quantity
which is clearly undesirable.
The present invention seek to provide an improved form
o~ distribution system.
Accordingly the present invention provides a distribution
system for conveying flowable material from a source
downstream to a plurality of successive user locations,
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Comprising: a conveyor means having a plurality of
successive, elongate primary conveyor sections each
of which is vibratable for conveying said material
towards a respective one of sai~ locations, each conveyor
section having a product-carrying surface tilted
relative to the horizontal about the longitudinal
axis of the conveyor section whereby said product tends
to gravitate towards the lower side edge region of said
surface as the product travels along said section and
a side wall upstanding on said lower side edge region
for retaining the product on the conveyor section; and
wherein each said side wall has an opening for allowing
product to fall from said conveyor section; and a
plurality of vibratable secondary conveyor sections for
receiving the fallen product and conveying said product
to each said user location.
Advantageously, each of said secondary conveyor sections
is independently operable. The primary conveyor
sections are preferably cumulatively operable in a
downstream direction, that is where all of the primary
conveyor sections are switched off then the switching on
of a primary conveyor section at any point in the conveyor
line automatically switches on all the primary conveyor
sections upstream of that point.
In a preferred embodiment of the present invention the
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downstream end of each primary conveyor section overlaps
the immediately following conveyor section and has its
downstream end cut away at a preselected acute angle to
the side wall, the angle preferably being 45 . Each
S conveyor section is vibrated at a frequency less than the
natural resonant frequency of the conveyor section. For
example where the natural frequency is 1500Hz the
conveyor section is vibrated at a frequency of typically
1410 Hz. The conveyor sections are preferably mounted
on rubber blocks and displaced in the direction of their
longitudinal axis against the action of the rubber
bloc~s by a single-acting piston-cylinder unit whose
piston rod abuts against a suitable surface on the
conveyor section. The unit is conveniently hydraulically
driven by a pump which applied hydraulic pressure pulses
to the unit at the required frequency, the return
resistance of the piston of the unit being such that the
piston rod is maintained in abuttment with the conveyor
section surface during the return stroke of the conveyor
section under the action of the rubber blocks. Of
course, any suitable resilient connection may replace
the use of ru~ber blocks.
The secondary conveyor sections are conveniently
vibrated by electromagnetic means to facilitate control
of the amplitude of vibration. This enables the feed
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rate of product along the secondary conveyor sections to be
controlled. As will be appreciated, such control can be
effected on either or both the primary or secondary
conveyor sections.
The present invention also provides a product storage
unit for connection in product feed line, the storage
unit comprising a lower conveyor section for conveying
product to an outlet of the storage unit; and an upper
conveyor section for conveying product from an inlet of
the storage unit, the upper conveyor section overlying
the lower conveyor section and having a plurality
of gates in its lower surface for allowing product to
fall onto said lower conveyor section, said upper and
lower conveyor sections being independently operable.
In a preferred form of the storage unit the gates are
independently controlled such that when the lower
conveyor section is switched off the gates can be
opened successively beginning with the gate furthest
downstream on the upper conveyor section to fill the
lower conveyor section progressively from the outlet
of the storage unit.
The provision of a storage unit in the product feed
line enables operation of the feed line upstream of
the storage unit to continue in the event of a
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temporary breakdown or blockage in the feedline downstream
of the storage unit.
The present invention is further describèd hereinafter,
by way of exa~ple, with reference to the accompanying
drawings, in which:-
Figure 1 is a side elevation of a food product feedline;
Figure 2 is a plan view of the distrubution system ofFigure 1;
.
Figure 3 is an end elevation of a preferred form of
. 10 distrubution system according to the present invention;
Figure 4 is a front elevation of the system of Figure
3; and
Figure 5 is a ladder network schematic diagram of the
control circuit of the distribution system of Figures
2 to 4.
In the drawings, Figures 1 and 2 show a feed line 10
for feeding a product such as crisps from an oven (not
shown in the drawings) to a distribution system 12 which
distributes the products to, for example,~ackaging
machines 14 located at respective user locations. The
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product is conveyed from right to left as seen in the
drawings from a deoiling conveyor 16 up a ~ucket
elevator 18 and along a transfer conveyor 20 into a
flavour drum 22. The product is discharged from the
flavour drum 22 onto an inspection belt 24 from which
it is carried by a further bucket conveyor to a storage
unit 28 which is described in greater detail below. In
the normal operation of the line the product passes
directly through the storage unit 28 and is carried by
a third bucket elevator 30 to the product distribution
system 12.
The distribution system is shown in greater detail in
Figure 2 and comprises a number, for example 3, of
conveyor modules 32, 34 and 36 associated with respective
user locations 38, 40 and 42 at which packaging machines
14 are located. The conveyor modules are arranged in
nested form to provide a continuous flow path of
product from the bucket elevator 30 to the user locations.
The conveyor modules are substantially identical and only
tne first conveyor module, module 32, is described
below in detail. It will be appreciated, therefore,
that the following description of module 32 applied
equally to modules 34 and 36.
The conveyor module 32 comprises an elongate vibratory
conveyor section which includes a product-carrying
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tray 44. The Tray 44 has a product-carrying base surLace
46 and two upstanding side walls 48, 50. The term
"wall" is used here to denote any suitable form of
barrier to retain the product on the tray 44. The tray
is orientated with its longitudinal axis substantially
horizontal (a slight downward tilt in the direction
of product feed may be provided to assist flow of the
product along the conveyor section) but is tilted
relative to the horizontal about its longitudinal axis
so that the side wall 50 adjacent the associated user
location is at a lower elevation than the opposite
side wall 48. The angle of tilt need not be excessive,
the angle being typically 10 and results in a
tendancy for the product to accumulate on the right hand
side of the tray 44, as seen in the direction of
product feed, against the side wall 50.
The side wall 50 is provided with an spening at or
adjacent the downstream end of the tray 44 to allow
product to fall from the tray 44 onto a tray 52 of a
secondary conveyor section 54 of a further conveyor module.
The latter is arranged with its longitudinal axis
preferably extending substantially at right angles to
the axis of the conveyor section 44 to carry product
to the associated packaging machine 14. The tray 52 of
the conveyor section 54 is conveniently horizontal
although again a slight tilt in the downward direction
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may be provided to assist product flow. In addition, the
elevation of the tray 52 relative to the tray 44 is such
that the product has only a relatively short fall,
typically one inch from the tray 44 to the tray 52.
Although the conveyor section 54 as shown comprises a
single tray 52 it may alternatively comprise a number
of narrow trays arranged side by side.
The downstream and edge of the tray 44 overlaps the
beginning of the tray of the next successive conveyor
module 34 with a vertical drop of typically one inch
between the two product carrying surfaces of the trays.
The tra~ 44 is resiliently supported on a series of
resilient members, preferably blocks of rubber or
plastics material and is vibrated by means of a single-
acting piston-cylinder unit located beneath the tray
and whose piston rod extends generally in the direction
of product flow and abuts a stop surface on the tray 44.
The piston-cylinder unit is preferably hydraulically
operated by a hydraulic motor which delivers pressure
plulses to the unit to extend the piston rod and drive
the tray 44 against the reaction of the resilient
blocks a pre-selected distance in the downstream
direction. Each time the pressure pulse is relieved the
resilient blocks draw the tray 44 back to its rest
position retracting the piston rod at the same time.
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The resistance of the piston rod to re~raction is arranged
such that the piston rod is maintained in abutment with
the tray stop surface during the return stroke of the
tray. The amplitude of vibration is adjustable by
adjustment of the motor to vary the piston stroke.
The pressure pulses are applied to the piston-cylinder
unit at a frequency below that of the natural resonant
frequency of the conveyor section. For example, with
a conveyor section having a natural resonant frequency
of 1500 Hz the pressure pulses are delivered at a
frequency of typically 1410 Hz. Actuation of the
piston-cylinder unit is controlled by a solenoid-actuated
control valve in the fluid line from the motor to the
unit so that the motor can be run continuously regardless
of whether the piston-cylinder unit is actuated to
vibrate the tray 44 or not.
The tray 52 of the secondary conveyor section 54 is
mounted in a similar manner to the tray 44 but is
-preferably vibrated using an electromagnet which is
pulse energised at a preselected pulse frequency to
provide the desired frequency of vibration of the tray
52. As will be appreciated, the vibratory action of
both trays 44 and 52 is generally in the direction of
their longitudinal axes to ensure product movement
towards the user locations. The use of an electromagnet
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to vibrate the tray 52 enables the amplitude of vibration
of the tray 52 to be controlled by varying the amplitude
of the energising pulses applied to the electromagnet.
Variation in the amplitude of the vibration varies
the rate at which product mOVeS along the tray 52 and
therefore provides an effective and simple way of
controlling the product feed rate to the associated
packaging machine 14.
As will be appreciated, each of the trays 44 and 52 may
be vibrated by means of a hydraulic or electromagnetic
drive system, as desired.
The control valves controlling the hydraulic fluid
~lines from the hydraulic motor of each conveyor module
to the associated piston-cylinder unit are solenoid-
actuated valves which are controlled through a relaycircuit by a respective product metering device 60, 62,
64 located adjacent the opening in the side wall 50
of each tray 44 to measure the quantity of product
falling from the tray 44 of each primary conveyor section
onto the tray 52 of the associated secondary conveyor
section 54. The product metering devices are
preferably photoelectric sensors which operate to
regulate the amount of product transferred to the
associated secondary conveyor system section. For
example, where the sensor 62 senses too much product on
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the tray 56 it closes the associated control valve of
the conveyor module 34 to deactuate the piston-
cylinder unit. Vibration of the primary conveyor
section of the module 34 therefore ceases and the flow
S of product onto the tray 56 is temporarily halted.
However, while the tray 56 continues to vibrate the
product which has accumulated on the tray continues
to be carried towards the packaging machine 40. Once
the sensor 62 senses that the product which has
accumulated on the tray 56 has been reduced to an
acceptable level it automatically opens the control
valve so that vibration of the tray of the conveyor
module 34 recommences and product is once more supplied
to the tray 56.
If, for any reason, product feed to one of the packaging
machines such as that fed by conveyor section 57 is
temporarily stopped by deactivating the drive system of
the conveyor section 57 it might be thouhgt that
continued vibration of the upstream primary conveyor
sections could result in an overflow of product onto the
tray 56. In practice this does happen initially but
the build up of product on the tray 56 adjacent the
primary conveyor section tray opening acts as a wall to
prevent further product exiting through the opening
onto the tray 56. The product thus continues to travel
downstream along the primary conveyor sections,
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bypassin~ the tray 56.
Conversely, if, for example, the vibratory drive system
of the conveyor module 36 is switched off, product
builds up at the upstream end of the module tray to form
a barrier accross the tray and, becuase of its angle
to the product flow path, deflect product through the
adjacent opening onto the tray 56.
Figur4 5 is a circuit diagram of the control circuit
showing the interconnections between the sensors 60, 62
and 64 and solenoids 70, 72 and 74 of the control
valves. Each sensor 60, 62 and 64 controls a respective
relay 76, 78 80 whose contacts in turn control the
assoc}ated solenoid 70, 72, 74. When the sensor 60
senses a lack of product it cloes an associated switch
60a to energise relay 76. The relay 76 has two pairs of
normally open contacts, one pair 76a closing to
energise the solenoid 70 of the associated control valve
and initiate vibration of the tray of the conveyor
module 32, and the other pair 76b closing to close the
power supply circuits 82, for example for the bucket
elevator 30 preceding the distribution system to supply
product to the first conveyor module 32. The sensor 62,
on sensing a lack of product closes an associated switch
62a to energise a further relay 78. This relay has two
pairs of contacts, one contact pair 78a closing to
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energise the solenoid 72 of the control valve to initiate
vibration of the tray of the second conveyor module 34,
and the other contact pair 78b closing to energise
the relay 76 and thus solenoid 76 of the control
valve of the preceding conveyor module 32. This ensures
that the trays on both the conveyor module 32 and 34
vibrate to supply product to the secondary conveyor
section 57. The third sensor 64 operates in similar
manner. On sensing a lack of product on the tray 57 it
closes an associated switch 64a to energise the associated
relay 80. This relay has two contact pairs, 80a and 80b.
The contact pair 80a control the solenoid 74 of the
control valve of the third conveyor module 36 while the
contact pair 80b control the relay 78. Since the relay
78 in turn also controls the relay 76 the energising
of the relay 80 results in the drive systems for the
trays of each of the conveyor modules 36, 34 and 32 being
energised to vibrate all of the trays carrying food
product to the tray 57 of the secondary conveyor section
59. The circuit of Figure 5 is therefore arranged to
ensure that where any one sensor senses a lack of
product on the associated secondary conveyor section the
drive systems of all of the conveyor modules upstream of
that secondary conveyor section are energised to carry
product to that section.
In a modified form of the distribution system each
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primary conveyor section feeds, for example two
packaqing machines or a packaqing machine having two
hopper inlets. This is effected as shown in Figures 3 and
4, by providing two secondary conveyor sections 100 and 102
which are fed from the same primary conveyor section
104 through a chute 106. Each secondary conveyor
section 100, 102 is independently vibrated by means of
a respective electromagnet 108, 110 so that the two
hopper inlets of the same or respective packaging
1~ machines can be fed at differing rates.
Referrinq again to Figure 1 the product feed line
includes, as mentioned earlier, a storage unit 28. This
unit comprises lower and upper conveyor sections 120, 122
which are similar to the conveyor modules previously
described with reference to the distribution system
12. The lower conveyor section 120, however, forms the
base of a container 124 in which the product can
accumulate. The storage unit has an inlet 126 through
which product is fed to the upper conveyor section 122.
The latter has a number of gates provided in its base
which can be opened to allow product to fall through into
the container 124. The storage unit has an outlet 128
which is arranged at the downstream end of the lower
conveyor section 120. Normally, in product feed lines
if ablockage occurs, for some reason, in the feed line
then the flow of product has to be stopped at source.
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~here the source is an oven, for example where the product
being fed is crisps or the like, any blockage in the feed
line means that the oven has to be shut down and as will
be appreciated, this is a time consuming and relatively
expensive operation. The provision of the storage unit
28 in the product feed line allows the operation of the
oven and the feed line upstream of the storage unit 28
to continue for a period when a blockage or stoppage
occurs in the line downstream of the storage unit 28. If
the lower conveyor section 120 of the storage unit is
deactuated then product will accumulate in the container
124 until the storage unit is full. The time to fill the
container will, of course, depend upon the size of the
container and the rate of feed of product along the line.
However, a typical time of fifteen minutes is normally
adequate to enable any temporary stoppage downstream of
the storage unit to be cleared.
Control of the gates in the upper conveyor section 122
is preferably effected such that when the lower conveyor
section is deactuated the gates are opened successively
beginning with the gate nearest the downstream end of
the upper conveyor section 122 to fill the container
124 with product from its downstream end. This ensures
that when the lower conveyor section 120 is reactuated
to recommence product feed downstream of the storage unit
product is immediately available at the outlet 128.
