Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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A Method and an Arrangement for Dispensing a Particulate Detergent
This invention relates to a method for the automatic quantity-controlled
dispensing of a particulate detergent from a storage container into an institutional
washing or dishwashing machine, the detergent being mixed with water and the
resulting lllixlule being introduced into the washing or dishwashing machine.
S Methods of this type are preferably applied in institutional dishwashing or
washing processes. The laundry or dishwashing detergent - also referred to
hereinafter as the "product" - is permanently held in a sufficient quantity in astorage container and is automatically added to the fresh water or to the circulating
water as and when required. To this end, dispensers and dispensing methods have
been developed for introducing powder-form detergent under control into the
particular machine, for example into the dispensing compartment of an institutional
dishwashing machine. One such dispensing method is known from DE 37 21 381
Al. In this case, a predetermined volume is introduced into the dispensing
col"pal l",ent of the powder dispenser and is flushed with water into the washing
or dishwashing machine which is generally located beneath the dispenser. This
volumetric dispensing process ple~upposes that the products used always have thesame appart;"l density. In addition, the angle of repose of the product is included
in this volumetric dispensing method. Unfortunately, variations in flow behaviorand in the particle size distribution lead to different angles of repose and hence to
inaccurate dispensing. Although the inaccuracies in dispensing are acceptable inpractice, there is a need for more accurate dispensing to optimize detergent
consumption.
Automatic dispensers for gravimetric precision filling systems are also
known. In their case, the product drops from a dispensing chute into a dispensing
container with a pneumatic closure flap. The dispensing container so to speak
forms the balance pan of a precision weigh feeder. When the required weight is
reached, the closure flap opens and the product drops into a portion container.
This process is unsuitable for dispensing laundry or dishwashing detergents.
If the quantities normally used in institutional washing or dishwashing processes,
for example 500 g, are flushed from the portion container with water, the product
CA 02204784 1997-0~-07
becomes lumpy and cannot be transported into the machine by standard pumps or
through standard pipes. In addition, the product tends to cake in the dispensingchannel which makes it initially difficult and ultimately impossible to dispensefurther quantities of detergent.
Accordingly, the problem addressed by the present invention was to provide
an inexpensive dispensing method of the type mentioned at the beginning by whichdetergent could readily be dispensed with precision in the quantities normally used
for institutional washing or dishwashing processes.
According to the invention, the solution to this problem is characterized in
that the laundry or dishwashing detergent is delivered continuously or in portions
to a balance pan of a balance and, when the required weight determined in advance
is reached, the detergent is transferred from the balance pan to a mixing vessel,
water is allowed to flow into the mixing vessel at the same time and a ratio of at
most 5 kg of detergent introduced per minute to 8 litres of water per minute is
m~int~ined. It is particularly important that the detergent is introduced into the
mixing vessel at the same time as the water and that the ratio of detergent to water
mentioned above is m~int~ined. Accordingly, the quantity of product to be
dispensed is not suddenly combined with water all at once, but only gradually. In
this way, the product is inexpensively dispensed into the machine in exact quantities
by weight without any flushing difficulties or caking occurring. This dispensingof exact quantities by weight enables d~lelgell~ consumption to be monitored andoptimi7f~1
In one advantageous embodiment of the invention, the detergent-to-water
ratio can be adapted to the particular product. Thus, if products produced by spray
drying are to be dispensed, only at most 2.2 kg per minute should be introduced
into the mixing vessel for a water inflow rate of 8 liters per minute. In the case
of products with an apparent density of more than 600 g/l, so-called heavy
powders, this limit is higher, i.e. at 5 kg of product per minute, again based on a
water inflow rate of 8 liters per minute.
To enable the product-to-water ratio to be readily established, the detergent
is delivered to the mixing vessel positioned beneath the balance pan through an
outlet in the balance pan provided with a controllable closure and the outlet is
CA 02204784 1997-0~-07
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opened partly or completely according to the required detergent discharge rate. The
outlet may be formed, for example, by a flap or slide.
If the d~lergelll drops through several openings in the storage container onto
a balance pan positioned underneath, it is of advantage for the balance pan to
assume the form of a funnel with an opening at its lowest point. The adjustable
closure can then be arranged over this opening.
Particularly effective mixing of the detergent with the inflowing water in the
mixing vessel and correspondingly problem-free dispensing of the product into the
particular machine is achieved if the water is allowed to flow tangentially into the
mixing vessel. The product and the water are mixed thoroughly with one another
without any need for an additional aid, for example a stirrer.
The detergent storage containers for institutional washing or dishwashing
machines generally hold relatively large quantities of product, for example 60 kg.
The container in which the product is sold, for example a 250 kg sack, is often
positioned above the storage container of the dispenser and fills it with product as
and when required. Because it contains hygroscopic components, the product
stored for a prolonged period in the storage container and in the sack tends to cake
and to form lumps. The agglomerates can be troublesome both during the transfer
of the product from the storage container to the balance pan and during its gradual
delivery according to the invention into the mixing vessel at the same time as the
water. This particular problem can be solved by allowing the detergent to trickle
through openings in the bottom of the storage container onto the balance pan
positioned underneath, a stirrer turning immediately above said openings. The
openings in the storage container are advantageously of at most such a size that the
lumps and agglomerates typically occurring are unable to pass through the
openings. The stirrer turning above the openings breaks up the agglomerates so
that only fine particles trickle onto the balance pan.
In another embodiment of the invention, the product undergoes preliminary
volumetric dispensing. To this end, the detergent drops through the openings - in
the form of dispensing holes - onto a collecting pan positioned underneath from
which the portions thus formed are pushed over the edge of the collecting pan and
allowed to trickle onto the balance pan. Product trickles through each dispensing
CA 02204784 1997-0~-07
~ . .
hole until a frustoconical unit with the corresponding angle of repose comes up
against the edge of the dispensing hole. More powder is only able to flow
downwards through the hole after portioned quantities of product already presenthave been pushed aside. This volumetric dispensing process is described in detail
in DE 37 21 381 Al.
The method according to the invention can be carried out in different ways.
In a first variant, the entire quantity by weight of detergent required for a wash
cycle or dishwashing step is dispensed in a single step into the mixing vessel and
from there into the washing or dishwashing machine. This is basic dispensing in
the context of the invention.
According to the invention, the detergent can also be dispensed as required
and, at the same time, the quantity by weight dispensed can be monitored. To this
end, a fraction of the quantity by weight of detergent required for a wash cycle or
dishwashing step is introduced into the mixing vessel and from there into the
washing or dishwashing m~hine, the conductivity of the liquor is measured in themachine and the process is repeated until the measured conductivity has reached a
set value. In this variant, therefore, the individual portions are not weighed to
determine the total amount of product required, but instead to measure
consumption. The quantity by weight dispensed can be indicated, stored or printed
out at the end of a working day. The particular demand for product and any
malfunctions in the washing or dishwashing process can easily be identified. In the
practical application of this variant, for example, 10 g of product are added inpulses, the pulses are counted and the addition of these portions is stopped when
the conductivity measured in the particular machine has reached its set value.
The soil to be removed binds part of the laundry or dishwashing d~lelg~
If there are relatively large amounts of soil to be removed, the set conductivity
value is only reached after a relatively large amount of product has been dispensed.
In this variant of the process according to the invention, therefore, the detergent can
be dispensed as required and the quantity by weight of consumed product can be
monitored at the same time.
The present invention relates not only to a dispensing method, but also to
a dispensing arrangement for carrying out this method comprising a storage
. CA 02204784 1997-0~-07
container and a mixing vessel connected to a water pipe. With this dispensing
arrangement, the problem addressed by the invention, as stated above, is solved by
a balance pan of a balance positioned above the mixing vessel and by a controllable
closure for an outlet opening in the balance pan which is designed to open partly
S or completely.
The closure is preferably a flap or slide.
If there are several openings in the storage container through which the
detergent drops onto the balance pan positioned underneath, the balance pan is
advantageously in the form of a funnel with an opening at its lowest point.
Particularly effective mixing and flushing in of the product are achieved by
a tangential direction of flow of the water pipe into the mixing vessel.
Lumps and agglomerates formed by prolonged storage of the product in the
storage container and the supply sack do not present any problems in another
advantageous embodiment of the arrangement according to the invention, in which
a stirrer is provided immediately above the outlet openings in the bottom of thestorage container.
One example of embodiment of the invention is described in detail in the
following with reference to the accol.lpallying drawings, wherein:
Figure 1 schematically illustrates an arrangement suitable for carrying out
the method according to the invention.
Figure 2 is a plan view of a plate with dispensing holes and a stirrer
arranged in the lower part of the storage container of the arrangement shown in
Fig. 1.
Figure 3 is a plan view of a collecting pan with a stripping mechanism
positioned beneath the plate shown in Fig. 2.
In the illustrated embodiment, a detergent is to be dispensed into one or
more washing machines of an institutional laundry. The detergent is introduced
from its supply container, a 250 kg sack, into a storage container 1 with a holding
capacity of 60 kg. A volumetric dispenser to be described in more detail
hereinafter is provided in the lower part of the storage container. In the interests
of clarity, Fig. 1 shows only one stirrer 3 which is driven by a motor 2 and which
breaks up the agglomerates caked together under the effect of moisture. With each
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volumetric dispensing step, around 30 cm3 of detergent drops down through
openings 4 in the bottom of the storage container 1 onto a funnel-shaped balancepan 5 connected to an electronic balance 6.
The particulate detergent trickles into the neck of the funnel which is
surrounded by a flap 7. When the set weight is reached, the flap 7 opens and thedetergent drops into the mixing vessel 8. In the illustrated embodiment, the
detergent is one produced by spray drying. The flap 7, of which the closure
mech~ni~m is controlled by an electronic unit 9, only opens far enough to allow 2.0
kg of detergent per minute to trickle into the mixing vessel. At the same time, 8
litres of water per minute are delivered tangentially into the mixing vessel through
a pipe 10.
A bypass leads upwards from the pump 12 into the mixing vessel 8. A
small part of the water/product mixture in the mixing vessel 8 is pumped back into
the mixing vessel through the bypass 11 so that an adequate volume of liquid is
present at the inlet end of the pump 12 in all operational states. This ensures that
the pump 12 does not deliver any air.
During or after t~rmin~tion of the transfer of product from the balance pan
5 to the mixing vessel, the water/product mixture is delivered by a pump 12 to one
or more institutional washing machines.
Figure 2 is a plan view of a plate 13 with three dispensing holes 14
arranged in the lower part of the storage container 1. During the dispensing
process, four arms 15 of a stirrer 16 rotate and break up moisture-agglomerated
detergent into small easy-to-dispense particles.
The particulate detergent drops through the dispensing holes 14 onto the
collecting pan 17 shown in Fig. 3. The frustoconical product portions 18 formed
are pushed by rotating strippers 19 over the edge 20 of the opening 4 so that they
trickle onto the balance pan 5.
In the illustrated embodiment, the dispensing holes are 18 mm in diameter
and the distance between the collecting pan 17 and the plate 13 is 10 mm. Other
dimensions are also possible, depending on the required volume of the portions 18
to be dispensed; the product-dependent angle of repose may also be taken into
consideration.
. - CA 02204784 1997-05-07
List of Reference Numerals
Storage container
2 Motor
3 Stirrer
4 Openings
5 Balance pan
6 Balance
7 Flap
8 Mixing vessel
9 Electronic unit (control)
10 Pipe
1 1 Bypass
12 Pump
1 3 Plate
14 Dispensing hole
15 Stirrer arm
1 6 Stirrer
17 Collecting pan
18 Portion to be dispensed
1 9 Stripper
20 Edge
