Note: Descriptions are shown in the official language in which they were submitted.
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FLUID METERING WITH A DISPOSABLE MEMBRANE TYPE PUMP UNIT
This invention relates to improvements in fluid metering and especially, but
not
exclusively, to the sanitary metering of very viscous fluids, for example
beverage
~ concentrates.
In the food sector, for example, there is often a requirement to dispense a
metered
amount of fluid foodstuff for use as such or in admixture with a diluent such
as water.
It is becoming increasingly important to be able to dispense fluids in
a'sanitary
manner where there is no possibility of outside contamination of the fluid
foodstuff or
where companies want to be able to assure the integrity of the fluid being
dispensed.
Commonly, the fluid foodstuff is supplied in a disposable container. For
sanitary
requirements to be met, it is desirable that the fluid contacts only
disposable parts of
the system, including the pump used to dispense the fluid. For this to be
economically viable, the pumping method should be simple and so relatively
inexpensive to produce.
In food dispense, and particularly in the beverage industry, there is a common
requirement to dispense an accurate ratiometric mixture of a concentrate and a
diluent. Common technologies involve measuring the flow of the concentrate and
then varying the diluent flow to achieve the correct mixture. This has the
disadvantage that it involves measuring the fluid flow of, in particular, the
concentrate. Common methods include the use of turbine flow meters and
differential pressure flow meters. These techniques are however not effective
for
measuring the flow of a highly viscous concentrate such as an orange juice
concentrate. Current methods of dealing with these viscous fluids are to meter
them
using peristaltic pumps or diaphragm type pumps integrated into manifolds.
While
these methods work well for many relatively viscous fluids, they do not work
well for
very highly viscous fluids. For example, peristaltic type pumps typically
become less
effective for fluids having a viscosity in excess of about 5000 centipoises.
Non-
disposable diaphragm pumps can be effective for dispensing very viscous fluids
but
the manifold valuing arrangements for disposable sanitary diaphragm pumps are
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commonly such that the fluid drag renders them unsuitable for use with very
viscous
fluids.
Examples of disposable sanitary diaphragm pump designs are proposed in US
Patent
6,455,263. However, these designs either utilise somewhat tortuous fluid inlet
paths
and additionally require simultaneous control of different pressures to the
three parts
of the pump - inlet valve, pump chamber and outlet valve (eg as shown in Fig
10)~ or,
alternatively, they utilise solenoid valves (e.g. as shown in Fig 1) that are
intended to
be disposed of with the other disposable pump components. The tortuous inlet
path
shown in the Fig 10 proposal would create considerable drag on a highly
viscous
fluid and hinder the performance of the pump resulting in a pump which is very
limited in operating speed. This problem could be overcome by pressurising the
source of fluid that is being dispensed by applying pressure internally to the
fluid
reservoir or by having a flexible reservoir and applying pressure externally.
However,
in sanitary systems, it is not acceptable to apply internal pressure and to
apply
pressure externally involves a much more complex and expensive system. The use
of
solenoid valves in the pump unit intended to be disposed of, as shown in Fig
1, has
the disadvantage that they are expensive.
It is the purpose of the present invention to provide an improved sanitary
fluid
metering device which incorporates a relatively cost-effective disposable pump
arrangement and which is capable of metering a highly viscous fluid.
According to a first aspect of the present invention, there is provided a
disposable
pump unit for receiving and metering a predetermined volume of fluid, the pump
comprising a body having a surface at which opens the mouth of a cavity formed
in ,
the body, an inlet port for the fluid opening at the surface adjacent to the
mouth of the
cavity whereby, when the inlet port is open, fluid can flow from the inlet
port into the
cavity via the mouth thereof, a first flexible membrane sealingly secured at
its
periphery to the surface and overlying the cavity and the inlet port, an
outlet port for
the fluid , there being a fluid flow passageway extending through the body
connecting
the cavity to the outlet port, and a second flexible membrane sealingly
secured at its
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periphery and overlying the outlet port, those portions of the first and
second flexible
membranes, where they overlie the inlet and outlet ports respectively, serving
as
closures for the ports.
The outlet port preferably also opens at the aforesaid surface, in which case
the first
and second flexible membranes may be integral with one another. Preferably, at
least
the first flexible membrane, i.e. the membrane that overlies the cavity and
the inlet
port formed in the body, is substantially non-stretchable and is dimensioned
such that,
during the fluid metering step, it can be urged by the actuating fluid into
contact with
substantially the whole surface of the cavity wall whereby substantially all
of the
fluid drawn from the reservoir during the fluid filling step is pumped out
during the
fluid metering step. To that end, the first flexible membrane (and the second
flexible
membrane where the two are integral with one another) may, for example,
comprise
polyamide film material. In a preferred embodiment, at least the first
flexible
membrane comprises a flexible film or sheet of an integrated laminate
comprising a
non-stretchable polymer, for example a polyamide, and an underlying heat-
weldable
polymer, for example a food-grade polyethylene, the latter having been heat-
welded
to the body so as to be sealingly secured thereto as aforesaid with the body .
comprising a moulding in a compatible food-grade polymer, for example a
polyethylene. An example of a suitable laminate is S77 available from Amcor
Flexibles Baricol. Preferably the laminate is preformed to a shape
substantially
similar to the shape of the surface of the pump cavity, such that it
substantially fully
evacuates the cavity without the need for the membrane material to stretch.
Preferably
during storage and transportation the preformed shape of the laminate film
lies flush
with the concavely curved surface of the pump cavity thereby reducing the
susceptibility of the membrane to damage during transit.
In use, and in accordance with a second aspect of the invention, a disposable
pump
unit of the invention is detachably coupled to a re-usable pump actuator, with
the said
surface sealingly abutting the pump actuator, comprising a source of positive
and
negative pressure actuating fluid, preferably air, and first and second valve
actuating
means associated respectively with the inlet port closure and the outlet port
closure,
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the arrangement being such that, when the external surface of the first
flexible
membrane (which acts as a pumping membrane) is exposed to the source of
negative
pressure fluid, with the inlet port open and the outlet port closed, it is
drawn away
from the disposable pump body whereby fluid, such as a beverage concentrate,
is
. drawn, from a reservoir thereof via the inlet port, into substantially all
of the space
defined by the cavity and the first flexible membrane ("the fluid filling
step"). Then,
with the inlet port closed and the outlet port open, when positive pressure
fluid is
applied to the external surface of the first flexible membrane, the membrane
is urged
back towards and into the cavity and pumps the fluid from the cavity through
the said
passageway to the outlet port ("the fluid metering step"). There may be a
variable
downstream flow restrictor to enable the same fluid metering rate to be
achieved for
different viscosity fluids with the application of the same positive actuating
fluid
pressure. Alternatively, the fluid pressure could simply be varied or a
combination of
variable downstream flow restrictor and variable fluid pressure could be used.
The
aforementioned variable restrictors and or pressure allow the outlet flow of
the
pumped fluid to be varied, or alternatively allow the output flow to be
maintained
substantially constant while fluid properties, for example temperature,
change.
The first valve actuating means associated with the inlet port closure is
preferably an
axially movable armature that extends into the volume subject to positive and
negative pressure and seal is provided where the armature protrudes into that
volume;
preferably the seal is a rolling diaphragm type seal. The second valve
actuating
means is likewise preferably an axially movable armature and a like seal may
also be
provided. Provision of these seals additionally prevents dirt ingress into the
valve
actuators and enables use of cleaning fluids without the danger of the fluids
affecting
the valve actuators, which may be electrically driven.
Preferably, a disposable pump unit of the invention comprises a body having a
plurality of cavities each having respective inlet ports, outlet ports and
flexible
membranes whereby, when coupled to a pump actuator, fluid may be drawn into at
least one of the cavities whilst simultaneously being pumped out of another.
In this
way, the unit may, where required, be used to meter varying predetermined
volumes
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of fluid in a substantially continuous and efficient way. Preferably, the body
has a
pair of cavities. Where there is a plurality of cavities, the simultaneous
fluid filling
and fluid metering steps may be of different duration such that when one
dispensing
step from one of the cavities is complete the other is ready to commence, or
has
already commenced, its dispensing step; this may be achieved by, for example,
suitably adjusting the negative and positive actuating fluid pressures by
means of
adjustable pressure regulators.
Preferably, in a disposable pump unit of the invention, the fluid
flow~passageway
extending through the body and connecting the cavity to the outlet port
terminates at
one end at a generally concave wall defining the cavity, the wall having
formed
therein a plurality of passageways that communicate with the fluid flow
passageway
thereby to inhibit, during the fluid metering step, the formation of occluded
regions of
fluid between the cavity wall and the first flexible membrane and thus ensure
that
substantially all of the fluid drawn from the reservoir thereof during the
fluid filling
step is pumped out during the fluid metering step. Each of the plurality of
passageways is preferably a groove.
The~combination of a disposable pump unit of the invention and a re-usable
pump
actuator may constitute a beverage dispenser as is more particularly described
in our
co-pending PCT application of even date, the pump unit serving to meter a
predetermined amount of a beverage concentrate, for example orange
concentrate,
which is then mixed with water, preferably in a predetermined ratio, delivered
by the
dispenser. For that purpose in particular, the body of the disposable pump
unit
preferably incorporates a diluent, e.g. water, inlet communicating with an
outlet
passageway formed in the body connected to the outlet port whereby, as fluid
flows
from the outlet port through the outlet passageway, it mixes with the diluent
and is
then dispensed into a receptacle such as a cup or glass. Preferably downstream
of the
outlet port of the pump cavity and immediately upstream of the diluent inlet
are a
number of obstructions in the flow path adapted to break up of the pumped
viscous
fluid to aid mixing with the diluent. The outlet passageway preferably
includes
means, for example a static turbulator, to assist the admixture of the fluid
and diluent.
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Further, there may be provided means to adjust the diluent flow rate and
feedback
means so as to ensure substantially constant ratiometric mixing at a target
dispense
rate.
The pump actuator includes a complementary surface that abuts the aforesaid
surface
of the disposable pump unit. Both surfaces are preferably substantially
planar. An
essential function of the pump actuator surface is to control the degree to
which the
first flexible membrane can be drawn away from the disposable pump body and
therefore in part to define the predetermined metered volume of fluid.
Preferably, the
surface of the pump actuator also has at least one recess (the number-
corresponding to
the number of cavities in the disposable pump body) defined in it for
receiving the
first flexible membrane during the fluid filling step, the recess wall serving
to limit
movement of the membrane. The cavity(ies) of the disposable pump unit and
recesses) (if any) of the pump actuator are preferably concave in form.
Preferably, each pump actuator has associated with each recess a means of
detecting
whether the or each recess is full of fluid or is empty. Preferably the
detecting means
comprises ultrasonic transducers, the variance in signals from which indicate
the
volume of fluid within each recess.
Another function of the pump actuator is to provide actuating means for the
closures
of the inlet and outlet ports. The actuating means for the inlet preferably
comprises a
solenoid-operated armature which, by means of a compression spring, urge part
of the
respective flexible membrane into sealing contact with the inlet port in order
to close
it, but which assume, when the solenoid is energised, a spaced position from
the
membrane when the port is required to be open. It will be recognised to those
skilled
in the art that other conventional actuation means, for example pneumatic,
could be
used to drive the armature in place of the solenoid described above. In a
preferred
arrangement the valve actuating means associated with the outlet port closure
is
capable of affecting a variable, pre-selected, degree of opening of the outlet
port. This
may be achieved by using, for example, a stepper motor or a variable end stop
solenoid associated with an armature or other actuator that acts upon the
second
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flexible membrane where it overlies the outlet port. This feature enables the
disposable pump unit to control the outlet flow rate as desired depending upon
the
viscosity of the fluid being metered. For example, with a relatively higher
viscosity
fluid, it may be desirable to have the outlet fully open in order to achieve
the desired
outlet flow rate and hence the required ratiometric mixing control with a
diluent such
as water, whereas with a relatively lower viscosity fluid it may be desirable
to have
the outlet oily partially open for that purpose.
Alternatively, for example, the armatures may be pneumatically operated. In
order to
improve the fluid seal between the ports and the flexible membranes in the
port-
closed position, each port is preferably surrounded by a raised lip.
Preferably the
actuating means are provided with soft tips, for example of a silicone rubber,
which
do not damage the membrane and provide an even pressure on the raised lip.
The disposable pump unit is preferably permanently connected to, or integral
with, a
reservoir containing the fluid so that, once the reservoir is empty or
otherwise needs
to be changed, the combined reservoir and pump unit are disconnected from the
pump
actuator and may be disposed of. A replacement reservoir/pump unit may then be
connected to the pump actuator. Preferably a closure is provided between the
pump
unit and the reservoir such that the reservoir and disposable pump unit may be
shipped together whilst preventing the migration of fluid into the disposable
pump
unit. Once in situ and connected to the pump actuator the closure is moved
from a
closed position in which flow between reservoir and disposable pump unit is
blocked
to an open position in which fluid may flow from the reservoir to the
disposable
pump unit. Especially in the drinks dispense context, the reservoir and
disposable
pump unit is preferably refrigerated by a refrigeration system comprised in
the re-
usable part of a drinks dispense machine and which may also serves to cool
said
diluent. In a preferred arrangement, the action of loading and unloading the
disposable pump unit from the pump actuator automatically opens and closes the
closure respectively.
It will be appreciated that the metered fluid comes into contact with only
components
of the disposable pump unit and, therefore, that the pump actuator may be
continually
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re-used without the need to clean it regularly. Thus, the pump actuator will
be part of,
for example, a fixed drinks dispense machine installed in a bar, restaurant or
the like,
it being possible for a given machine to dispense different beverages
depending on
the nature of the fluid concentrate contained in a selected
reservoir/disposable pump
unit. Because different concentrates will usually require different degrees of
dilution,
the disposable pump unit preferably includes an identification means and the
re-
usable pump actuator includes reading means for automatically reading the
identification means whereby the combined pump/pump actuator, for example a
drinks dispense machine, may adapt its dispense mode, e.g. diluent flow rate,
and/or
provide audio and/or visual information to the user in dependence upon the
characteristics identified. Such characteristics may include, for example, one
or more
of the viscosity of the fluid to be metered in a particular case, its type
(e.g. orange
juice or otherwise), its shelf life/expiry date and the desired dilution
ratio. The
identification means and the reading means may be based on, for example, radio
frequency identification (RDIF) technology, Electro-Erasable-Programmable-Read
Only Memory (EEPROM) chips, bar code technology or colour-sensing technology,
the general nature of all of which are known. Preferably the reusable pump
actuator
has associated therewith a read/write device that is capable of both reading
information from an identification means associated with the disposable pump
unit
and writing information to said identification means.
According to a third aspect of the present invention, there is provided a
disposable
pump unit as defined above adapted for mixing two or more fluids, especially
viscous
fluids, the body defining two or more said cavities and an inlet port
associated with
each cavity and with reservoirs for the respective fluids, and a common outlet
associated with the cavities, whereby the fluids may, in association with a re-
usable
pump actuator, be dispensed simultaneously and mixed. Such a unit has a number
of
diverse applications, and we mention by way of example the mixing of the two
precursor materials of epoxy resins (e.g. "Araldite" - Registered Trade Mark).
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Embodiments of the invention will now be described by way of example only,
with
reference to the accompanying drawings in which;
Figure 1 is a perspective view of a disposable pump unit of the invention;
Figure 2 is a longitudinal cross-section of the disposable pump unit of Fig 1;
Figure 3 is a perspective view of a pump actuator for assembly with the pump
unit
shown in Figs 1 and 2;
Figure 4 is a cross-section of the assembled pump unit and pump actuator;
Figure 5 is a perspective view of the pump unit shown in Fig 1 additionally
having a
diluent inlet;
Figure 6 is a similar view to Fig 5, but in which the pump outlet has an
integral
convoluted path mixing section;
Figure 7 is a perspective view of a disposable pump unit of the invention
showing the
channels provided for prevention of occluded volumes of fluid in the pump;
Figure 8 is.a perspective view of a disposable pump unit of the invention
showing the
closure between the pump unit and the reservoir; and
Figure 9 is a perspective view of a pre-formed membrane for use with the the
disposable pump unit.
Refernng to Figure 1 and 2, a dual-chamber disposable pump unit 100 is shown.
A
fluid inlet 14 splits to feed each of the two pump cells 1a, lb comprised in a
rigid
body 2 having on a substantially flat surface thereof an area 3 containing a
chamber
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inlet port 4, the inlet port 4 being surrounded by a raised lip 5, and a
concave cavity 6
defining one side of a pump chamber 7. The second side of the chamber 7
comprises
a membrane 8 made of a flexible sheet material, e.g. low density polyethylene
(LDPE), sealingly secured about its periphery to the aforesaid surface of the
body 2
5 so as to enclose each fluid inlet area 3 and their respective concave
cavities 6 such
that fluid can pass from the inlet port 4, when open, to the respective
concave cavities
6. Located in each concave cavity 6 of each pump chamber la, lb is an array of
chamber outlets 9. Each chamber outlet 9 is in fluid communication with a
closable
outlet port 10 surrounded by a raised lip 1 l.The flow paths from the two
closable
10 ~ outlet ports 10 converge together into a single outlet 12. The two
closable outlet
ports 10 and the outlet 12 are together sealingly enclosed by a membrane 13
comprising flexible sheet material, shown to be integral with the membrane 8,
.
secured about its periphery to the aforesaid surface of the body 2.
Referring to Figure 3, a non-disposable pump-actuating unit 200 for the dual
chamber
pump unit 100 is shown. The actuating unit 200 comprises a rigid body 15
containing two concave cavities 16, each surrounded by a gasket seal 17. The
concave cavities 16 and the gasket seal 17 are shaped such that they match the
shape
of the pump cells 1 a, lb so that when placed in contact with them they form a
seal
around the circumference of the pump cells la, lb. Located within each cavity
16 is a
compressed air inlet/exhaust port 18 defined in part by cross-shaped channels
extending over a substantial basal area of the cavity 16. Also located within
each
cavity 16 is a solenoid-operated armature 19 which extends through the body 15
and
into the cavity 16. A pair of armatures 20 also extends through the body 15
adjacent
to the cavities 16.
Referring to Figures 1, 2 and 4, the pump-actuating unit 200 is shown in
Figure 4 to
be releasably connected to the disposable pump unit 100 to form a complete
pump.
The cavity 16 in the unit 200 together with the membrane 8 forms an actuating
chamber 21 connectable alternately to supplies of negative and positive
pressure air
via a passageway 22. Each cavity 16 in the pump-actuating unit 200 and its
opposed
cavity 6 in the disposable pump unit 100 together define a fixed volume of
fluid that
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will be displaced on each cycle of the pump. The sequence of operation of the
pump
is that each armature 20 extends so as to urge the membrane 13 locally onto
the
respective raised lips 11 of the outlet ports 10 thus closing the pump chamber
outlet,
and the armature 19 is spaced from the membrane 8 such that the flow path
between
the inlet port 4 and the concave cavity 6 is open. Armatures 19 and 20 have
associated seals 19a, 20a, which prevent ingress of any substances past the
armatures.
A first source of pump actuating fluid at a negative pressure, ie below
ambient
pressure, is connected to the actuating fluid port 18 via the passageway 22,
the
application of the negative pressure causing the flexible membrane 8 to be
drawn
towaxds and into the cavity 16 thereby drawing fluid into the latter from a
reservoir
(not shown) via the inlet 14 and the inlet port 4, the inlet port 4 being held
open by
the negative pressure tending to lift the membrane 8 locally away from the
inlet port
4. The cross-shaped channels of the port 18 ensure that the membrane 8 can be
drawn fully into the cavity 16 and prevents the membrane 8 from blocking the
port 18
before the membrane 8 is substantially fully withdrawn into the cavity 16.
When the
membrane 8 is fully drawn into the cavity 16 and the volume defined by the
cavity 16
and the cavity 6 is filled or substantially filled with the fluid to be
dispensed, the
armatures 19 and 20 are actuated such that armature 19 is moved towards the
pump
cell,.locally pressing the membrane 8 against the raised lip 5 of the inlet
port 4 to
close the flow path between the inlet 14 and the pump chamber 7, and armature
20
moves away from the outlet port 10 allowing the membrane 13 to move away from
the outlet port 10 of the pump cell outlet (12, Figure 1). Substantially at
the same
time, positive air pressure is applied to the membrane 8 via the port 18 which
urges
the membrane 8 towards and substantially fully into the cavity 6 whereby the
fluid is
pumped out through the outlet 12 via the outlet port 10. The pump
filling/dispense
cycle may then be repeated. The outlet armatures 20 are attached to stepper
motors
20b which can vary the position of the each 20 in relation to the raised lip
11 of its
respective outlet port 10 thereby allowing the opening of the outlet valve to
be
controlled to vaxy the outlet flow of the pump.
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In operation, the two pump cells may be operated in opposite phase such that
when
one is dispensing the other is filling, the filling cycle preferably being
faster than the
dispense cycle such that there can be a slight overlap of the dispensing
cycles to
ensure constant output. If there are more than two pump cells then it is not
necessary
for the filling cycle to be faster than the dispense cycle.
Referring tb Figure 5, a pump unit is shown which is similar to that shown in
Figure 1
and operates in the same manner, but which has the additional feature of a
diluent
inlet 23 through which a diluent enters the pump cell and mixes with the
pumped
fluid to pass with it through the pump cell outlet 12 whereby diluted fluid is
dispensed. The flow of the diluent is controlled by means of an external
control valve
(not shown) which may be variable and controlled to give a constant
ratiometric
mixture of pumped fluid to diluent.
Referring to Figure 6, a pump unit is shown which is similar to that shown in
Figure 5
and operates in the same manner. However, in addition, it comprises a mixing
section
24 downstream of the point at which the diluent is added. Where the pumped
fluid is
of a high viscosity (e.g. above 10,000 centipoises) it becomes increasingly
difficult to
obtain a homogeneous diluted fluid; the convoluted path 25 of the mixing
section 24
is designed to shear the viscous fluid and create turbulence to ensure that
the two
components mix fully.
Referring to Figure 7 a rigid plastic pump unit is shown comprising of a fluid
inlet 14
leading to two chamber inlet ports 4 from which there is a flowpath to the
concave
cavity 6 and its associated chamber outlet 9. Provided in surface of the
concave cavity
6 and the flat area 3 are recessed grooves 26 which, should the flexible film
(not
shown) trap an occluded area of the pumped fluid remote from the chamber
outlet 9,
there will always be a channel for the fluid to be forced out of ensuring that
the
chamber is fully emptied every, thus giving a repeatable volumetric output.
The pump
unit shown in this figure has had all excessive plastic removed and designed
for
production by injection moulding techniques.
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Referring to Figure ~ the rigid plastic pump unit of Figure 7 is shown further
comprising an integrated static mixer 27 which is formed as a feature of the
plastic
moulding enclosed by the flexible film which is heat welded thereover.
Additionally
an array of obstructions 2~ are provided between the outlet ports 10 and the
static
mixer 27 such that the fluid is sheared immediately prior to it admixing with
the
diluent entering via diluent inlet 23. Once admixed with the diluent the fluid
passes
through the static mixer 27 and is dispensed therefrom as a homogeneous fluid.
In the fluid inlet (14, Figure 7) is a closure 29 which is rotatable by means
of lever 30
to open or close the flow from the reservoir (not shown) to the inlet ports 4.
Referring to~ Figure 9 a pre- formed flexible membrane suitable to be heat
welded to a
pump zone of the invention is shown.
