Note: Descriptions are shown in the official language in which they were submitted.
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METHOD AND APPARATUS FOR PUMP CONTROL
BACKGROUND OF INVENTION
1. Field of Invention
This invention relates to methods and apparatus for pump control.
2. Related Art
Volume control for beverage forming machines, such as coffee brewers, can be
important to the quality of the formed beverage(s). For example, standard drip
coffee makers
typically include a water reservoir that is filled with a desired volume of
water by a user that
is used by the machine to make a volume of coffee. Such reservoirs often
include a sight
glass or other arrangement that allows the user to define the amount of water
in the reservoir.
As a result, the user may have a certain amount of control over the amount of
water used by
the machine to make the coffee beverage.
SUMMARY OF INVENTION
The inventors have appreciated that some beverage forming machines, such as
single
serve coffee brewers, require an accurate water volume to form a quality
beverage, but do not
operate in such a way as to allow a user to control the amount of water
actually used. For
example, some coffee brewers have a water storage tank that holds sufficient
water for
several beverages. Although the user may be able to define the ultimate size
of the beverage
produced, the brewer itself controls the amount of water used to make the
beverage, e.g., by
automatically drawing a desired amount of water from a storage tank and
providing the water
for coffee brewing. Some such brewers use a flowmeter to determine the volume
of water
provided and control the operation of a water pump so that a controlled volume
of water is
used for brewing purposes.
In one aspect of the invention, a beverage forming system includes a beverage
forming apparatus adapted to fonn a beverage at least in part from a liquid.
The beverage
forming apparatus may include a pump adapted to cause liquid to flow from a
first location to
a second location, e.g., for use in brewing a coffee beverage. A controller
associated with the
system may be adapted to control the pump to operate based on an operation
index to deliver
a predetermined volume of liquid from the first location to the second
location, e.g., so that a
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carefully defined volume of water is used to make the beverage. In one
embodiment, the
operation index may represent the pump's ability to provide a volume flow rate
for given
voltage supplied to the pump. In one aspect, the controller may be adapted to
cause the pump
to operate during a calibration period, such as when the beverage forming
system is first put
into use by a user, to determine the operation index. The controller may
determine the
operation index based on a performance characteristic of the pump during the
calibration
period, such as a power supply characteristic of power supplied to the pump
during the
calibration period (such as a voltage provided to the pump) and/or a
performance of the pump
during the calibration period (such as a time for the pump to deliver a
specific volume of
liquid given a specific voltage).
In another aspect of the invention, a beverage forming system includes a
beverage
forming apparatus adapted to form a beverage at least in part from a liquid.
The beverage
forming apparatus may include a pump adapted to cause liquid to flow from a
first location to
a second location, e.g., for use in brewing a coffee beverage. A controller
associated with the
system may be adapted to control the pump to operate for an operation time and
deliver a
predetermined volume of liquid from the first location to the second location.
The operation
time for the pump may be determined based on an operation index, e.g., that
represents an
ability of the pump to provide a volume flow rate for a given voltage supplied
to the pump,
and/or may be determined based on a voltage to be supplied to the pump during
the operation
time. For example, if the voltage supplied to the pump varies, the controller
may adjust the
operation time to ensure that the pump provides a suitable volume of liquid.
In another aspect of the invention, a method for calibrating the operation of
a pump
used in a beverage forming machine includes providing a beverage forming
machine
including at least one pump adapted to cause liquid to flow from a first
location to a second
location. The pump may be operated for calibration purposes, and a performance
characteristic of the pump during operation may be measured. For example, it
may be
determined how long it takes for the pump to provide a defined volume of fluid
and/or a
voltage supplied to the pump during calibration. An operation index may be
assigned to the
pump based on the performance characteristic, and the operation index may be
used in
subsequent operation of the pump to control its operation. Thus, variations in
pump
operation may be accounted for, and the pump may be controlled to provide a
desired volume
of liquid, whether or not the desired volume is precisely the same as the
volume used in
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calibration. In one embodiment, the voltage or other characteristic of power
provided to the
pump during the calibration may be used to determine the operation index in
addition to at
least one other performance characteristic for the pump.
In another aspect of the invention, a method for controlling the operation of
a pump
used in a beverage forming machine may include providing a beverage forming
machine
including at least one pump adapted to cause liquid to flow from a first
location to a second
location. A power supply characteristic of power supplied to the pump to cause
the pump to
operate to deliver a predetermined volume of liquid may be determined, and an
operation
time for the pump to deliver a predetermined volume of liquid may be
determined based on
the power supply characteristic. The pump may then be operated according to
the determined
operation time. The power supply characteristic may be determined before the
pump
operates during the operation time, e.g., the voltage may be estimated, or the
power supply
characteristic may be detected during pump operation, e.g., the voltage
supplied to the pump
may be integrated, and the integrated voltage used to determine the operation
time.
These and other aspects of the invention will be apparent from the following
description and claims.
BRIEF DESCRIPTION OF DRAWINGS
Aspects of the invention are described below with reference to illustrative
embodiments, wherein like elements reference like numerals, and wherein:
Figure 1 shows schematic diagram of a beverage forming system in accordance
with
an aspect of the invention;
Figure 2 shows an exemplary lookup table for determining a pump operation
index in
accordance with an aspect of the invention; and
Figure 3 shows an exemplary volume flow rate vs. voltage curve for a pump in
an
illustrative embodiment.
DETAILED DESCRIPTION
Aspects of the invention may be practiced using any suitable pump/control
arrangement and/or with any associated beverage forming system. Several
different
embodiments are described herein for purposes of illustration. However, these
illustrative
embodiments should not be used to narrowly interpret the scope of the
invention. For
example, embodiments are described below in which a beverage forming apparatus
includes a
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water storage tank and a metering chamber, from which liquid is provided to a
brew chamber.
However, aspects of the invention are not limited to this type of arrangement.
For example,
aspects of the invention may be used in systems including no metering chamber,
e.g., water is
supplied directly from a storage tank to a brew chamber, and/or in systems
having no brew
chamber, e.g., systems in which a beverage is formed without brewing. In
addition, various
aspects of the invention are described herein, and these various aspects may
be used in any
suitable combination with each other, or alone.
In one aspect of the invention, a beverage forming system controller may
control a
pump, such as a water pump, to operate based on an operation index associated
witli the
pump. The operation index may represent an ability of the pump to deliver a
particular
volume flow rate, and thus the ability of the pump to deliver a specific
volume of liquid over
a corresponding pump operation time. As used herein, an "operation time" may
be any
suitable measure for a duration of operation for the pump, including a period
of time, a
number of pump cycles (e.g., shaft revolutions or strokes), a total power
delivered to the
pump, an integrated voltage applied to the pump, or other measure by which a
duration that
the pump is operated may be based. The operation index may be adjustable,
e.g., to allow the
controller to set the operation index for the pump at an initial start up
and/or at some time .
after the puinp has been put into service. Thus, the operation index may allow
the controller
to control the operation of the pump so that it delivers a predetermined
volume of liquid even
if the pump's performance characteristics (such as a nominal volume flow rate
or supplied
voltage) changes over time.
Also, the operation index may allow the controller to accommodate pump-to-
puinp
variation that may exist, e.g., when a pump is replaced in a beverage forming
system or as
between pumps in two different systems that include a same control
arrangement. For
example, although puinps may have the same design, specifications and be made
by the same
manufacturer, performance of different pump units of the same model may vary
widely, in
one case up to a 20% variation. Thus, one pump provided in one beverage
forming apparatus
may operate differently from another pump in another beverage forming
apparatus. For
example, one pump may provide a volume flow rate that is different from
another pump, even
though the power supply, water supply and other operation parameters are the
same. Thus, in
accordance with one aspect of the invention, the controllers in different
systems may be
otherwise configured in nearly identical ways, yet the controller in one
beverage forming
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system may use a first operation index for the pump in its system, whereas the
controller in
another system may use a second operation index for the other pump. As a
result, variations
between the two pumps may be accommodated, and the operation of the pumps
controlled so
that the pumps provide a desired volume of liquid in each system.
For example, in one embodiment, the controller may operate the pump for a
specific
operation time so that the pump provides a desired total volume, e.g., for
forming a beverage.
If the pumps in two different systems perform differently, the pumps will
provide different
total volumes of liquid if they are both run for a same operation time. As
discussed above,
volume control can be important in forming beverages, e.g., to provide
consistency, quality
taste or appearance, or other beverage characteristics. The operation index
may take
variations in pump performance into account and allow each controller to
control its
respective pump, e.g., determine an operation time for the pump, so that the
pump delivers
the same required volume in both systems.
In one embodiment, a controller may use a power supply characteristic of power
supplied to the pump to determine an appropriate operation time for the pump.
For example,
even if two pumps in two different beverage forming systems otherwise perform
identically,
if the two pumps are provided with different power voltages during operation,
the pumps will
typically provide different volume flow rates, in one exeinplary case
representing up to an
80% variation. Thus, the controller may take a power supply characteristic,
such as a voltage
of power to be supplied to the pump during operation, into account so that the
pump can be
controlled to accurately provide the desired volume of liquid.
In another embodiment, a controller in a beverage forming system may use both
an
operation index and a power supply characteristic to determine an operation
time for a pump.
By using both the operation index and power supply characteristic, the
controller may be
capable of accurately controlling the pump, even in the case of pump
performance and/or
power supply variations. For example, the controller may determine an
operation time for the
pump based on the operation index, and then make adjustments to the time
during pump
operation based on the voltage supplied to the pump.
In one aspect of the invention, a controller in a beverage forming system may
control
the pump to operate during a calibration period, and based on the performance
characteristics
of the pump determine an operation index for the pump. For example, at the
time a beverage
forming system is first operated, the controller may cause the pump to operate
to provide a
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specific volume of liquid, e.g., to fill a chamber in the system. The
controller may determine
a calibration time that corresponds to a time taken for the pump to provide
the volume of
liquid. Based on the calibration time (which may effectively represent a
volume flow rate for
the pump during the calibration period), the controller may assign an
operation index to the
pump. Thus, the operation index may represent the pump's ability to provide a
volume flow
rate. The operation index may be used by the controller to subsequently
control the pump
when delivering the specific voluine delivered by the pump during the
calibration period
and/or for other volumes. For example, during subsequent operation of the
puinp to deliver a
predeterinined volume, the controller may determine an operation time for the
pump to
operate to provide the predetermined volume. The pump may then be operated for
the
operation time, and stopped.
The controller may also take a power supply characteristic of power provided
to the
pump during the calibration period into account when determining the operation
index. For
example, the controller may determine a voltage for power supplied to the pump
during the
calibration period and use that voltage, together with the calibration time,
to determine the
operation index for the pump. Subsequently, the controller may use a voltage
supplied to the
pump with the operation index to determine an operation time for the pump.
Such an
approach may be useful in applications where the voltage provided to the pump
varies, e.g.,
because of operation of other parts of the system, such as a water heater, or
variations in line
voltage provided to the system, such as variations caused by the operation of
devices in the
electrical grid to which the system is connected.
. Figure 1 shows a schematic block diagram of various components included in a
beverage forming system 1 in an aspect of the invention. Water or other liquid
from a tank 2
may be provided by a water pump 52 to a metering tank or chamber 53. Operation
of the
water pump 52 and other components of the system 1 may be controlled by a
controller 51,
e.g., including a programmed processor and/or other data processing device
along with
suitable software or other operating instructions, one or more memories,
input/output
interfaces, communication buses or other links, a display, switches, relays,
triacs, or other
components necessary to perform desired input/output or other functions. The
chamber 53
may be filled with a desired amount of liquid by any suitable technique, such
as running the
water pump 52 for a predetermined time, sensing a water level in the chamber
53 using a
conductive probe sensor or capacitive sensor, detecting a pressure rise in
chamber 53, or
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using any other viable techniques. For example, the controller 51 may detect
that the
chamber 53 is completely filled when a pressure sensor 57 detects a rise in
pressure
indicating that the water has reached the top of the chamber 53. Water in the
tank may be
heated, if desired, by way of a heating element 61 whose operation is
controlled by the
controller using input from a temperature sensor 60. Water in the chamber 53
may be
dispensed via a tube 54 to a brew chamber 55 or other beverage forming
station. The brew
chamber 55 may include any beverage making ingredient, such as ground coffee,
tea, a
flavored drink mix, or other substance. Liquid may be discharged from the
chamber 53 by
pressurizing the chamber with air provided by an air pump 56 that causes the
liquid to be
discharged out of the tube 54. Completion of the dispensing from the chainber
53 may be
detected in any suitable way, such as by detecting a pressure drop with the
pressure
sensor 57, by detecting a water level change in the chamber 53, or using any
other viable
techniques.
In one embodiment, the controller 51 may control the pmnp 52 to deliver a
specific,
predetermined volume of water to the chamber 53 for beverage forming purposes
such that
the chamber 53 is not entirely filled. The controller 51 may control the
volume of water
delivered by the pump by causing the pump 52 to operate for a specified
operation time. For
example, operation of the pump 52 for a time period of 5-15 seconds may
provide a suitable
volume for preparation of a beverage, such as 6 ounces. As is discussed in
more detail
below, the controller 51 may determine the operation time for the pump based
on one or more
factors so as to provide close control of the volume delivered by the pump.
When filling the chamber 53 with water from the tank 2, the chamber 53 may be
vented by opening a line including a filter 58 and a valve 59. The filter 58
may prevent
undesired items, such as minerals, scale deposits or other, from interfering
with the operation
of the valve 59. A user may input commands or other information to the
controller 51, and/or
the controller 51 may provide information to the user via a user input/display
13. The user
input/display 13 may include an LCD or other suitable display, and/or one or
more operation
buttons, knobs or other devices that may be used to control the system
operation. A
sensor 32 may also communicate with the controller 51 and provide a low liquid
indication to
the controller 51 wlien a float 31 or other device is detected to be at or
below a specified level
in the tank 2. A low level indication may be provided to a user, e.g., via the
user
input/display 13, suggesting that the tank 2 be refilled.
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In one embodiment, the controller 51 may control the water pump 52 to operate
during a calibration period to assess the performance of the pump. This may be
done during
a first time that the system 1 is powered up and operated by a user (such as
the first time that
the user introduces water into the tank 2), and/or at a time after initial
start up (such as after
every 100 operation cycles, once every 6 months, etc.). The controller 51 may
assess the
performance of the pump during the calibration period, and then base its
subsequent control
of the pump on the assessment. As discussed above, in one embodiment, the
controller 51
may normally control the pump to deliver a specific, predetermined volume of
water to the
chamber 53 such that the chamber 53 is not entirely filled. After calibration
is performed,
control of the volume of water delivered by the pump 52 may be based on an
operation time,
which may be determined based on the assessment of pump performance during the
calibration period.
During the calibration period, the controller 51 may command to puinp 52 to
start
pumping with the chamber 53 completely empty. (The chamber 53 may be known by
the
controller 51 to be empty at a time when water is first introduced into the
system by a user, or
the controller 51 may completely drain the chamber, or request that the user
do so, by a drain
line not shown in Figure 1.) Alternately, the controller 51 may detect an
amount of water
present in the chamber 53 when the pump 52 starts operation during the
calibration period.
When a desired amount of liquid has been supplied to the chamber 53, e.g.,
when the
chamber 53 is detected to be completely full by detection of a pressure rise
by the pressure
sensor 57, or the controller 51 otherwise detects a desired volume of water
has been
transferred to the chamber, the controller 51 may stop operation of the pump
52. An
alternative is for the controller 51 to cause the pump 52 to operate for a set
period of time and
detect the amount of liquid delivered by the pump 52 to the chamber 53. In any
case, the
controller 51 may determine (or effectively determine) the volume flow rate of
the pump 52
during the calibration period based on the time elapsed during the calibration
period and the
volume delivered.
Based on the volume flow rate during the calibration period, the controller 51
may
determine an operation index for the pump that represents the pump's ability
to provide a
volume flow rate. This operation index may be used to determine operation
times for the
pump when subsequently controlling the pump to deliver other predetermined
volumes of
liquid. For example, in a subsequent operation, the controller 51 may control
the pump to
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deliver a volume that is 1/Z of the volume delivered during the calibration
period. The
operation index may be used to determine the operation time for the pump for
delivering the
smaller volume (which may be %z of the total time elapsed during the
calibration period (a
calibration time) where other operating conditions for the pump are the same).
(A
"calibration time" like an operation time, may be any suitable measure for a
duration of
operation for the pump, not just actual time, e.g., in seconds, but may be an
integrated
voltage, for example.)
Figure 2 shows one example of a lookup table approach that may be used by the
controller to determine the operation index. The lookup table may list a
series of calibration
times, e.g., 50 different calibration entries. (As discussed in more detail
below, the lookup
table in Figure 2 includes "volt-tics" which is a measure of the voltage
provided to the pump
over time. It will be understood that other measurements may be used, such as
seconds, etc.)
Once the calibration period is completed, the controller 51 may compare the
calibration value
obtained during calibration to the entries in the lookup table, and identify
that entry that is
closest to the calibration time. The position of the closest time in the list
may be assigned to
the pump as its operation index, e.g., if the 10th entry in the lookup table
is the closest to the
calibration time, the pump may be assigned an operation index of 10 for
subsequent control
of the pump.
In one aspect of the invention, the controller may determine the operation
index for
the pump based on a power supply characteristic of power supplied to the pump
during the
calibration period. The use of the power supply characteristic may be used in
lieu of other
pump performance characteristics, such as volume flow rate. For example, a
linear or other
curve 3 may be known for the pump that relates a volume flow rate for the pump
to voltage
supplied to the pump such as that shown in Figure 3. During calibration, the
controller 51
may determine the voltage applied to the pump during its operation, and use
the voltage to
determine an operation index (e.g., relating to a volume flow rate that
corresponds to the
voltage in the curve 3) for subsequent operation of the pump. Such an approach
may be
useful where voltage supplied to the pump varies due to operation of other
portions of the
beverage forming system or for other reasons. For example, a beverage forming
system may
be sold in two different countries which each have different electrical
standards with different
line voltages. The controller 51 may determine the voltage supplied to the
system, and use
this voltage to control pump operation.
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In another aspect of the invention, the controller may use two (or more) pump
performance characteristics to determine an operation index for the pump. For
example, the
controller may use both a volume flow rate provided by the pump and a voltage
supplied to
the pump to determine an operation index. Referring again to Figure 3, the
slope of the curve
3 may be known to be the same for all pumps, but pump-to-pump variations may
cause the
curve to be shifted (e.g., up or down as shown) for some pumps relative to
others.
Additionally, the curve may not be linear across all voltages. Thus, during
calibration, the
controller 51 may determine the voltage provided to the pump as well as the
volume flow rate
during the calibration period and determine the "shifted" location of the
curve 3 for the pump.
The shifted curve may be used to determine the pump's operation index for
subsequent
operation of the pump. In this embodiment, the operation index may relate to
the shifted
position of the curve 3 (e.g., define the "zero crossing" on the voltage axis
where a
hypothetical zero volume flow rate is provided) and be used to determine an
operation time
for the pump in subsequent operation based.on a desired volume to be delivered
and an
expected voltage to be supplied to the pump during the operation time.
In another embodiment, the controller 51 may use a lookup table such as that
in
Figure 2 to determine an operation index based on a volume flow rate and
voltage provided to
the pump. As mentioned above, the lookup table in Figure 2 includes
calibration times in
"volt-tics" which is a measure of integrated voltage provided to the pump
during the
calibration period. For example, in one embodiment, the controller 51 may
measure a current
voltage being applied to the pump at regular time intervals (such as every
"zero crossing" of a
60Hz power supply, or every 8.3 milliseconds), and sum the voltage
measurements until the
desired volume has been delivered to conclude the calibration period. As a
result, the "volt-
tic" measurement may provide a composite indication of time and voltage
applied to the
pump. The controller 51 may use the "volt-tic" measurement and compare it to
the volt-tic
values in the lookup table to determine the operation index, e.g., a position
of a volt-tic value
in the lookup table nearest that of the calibration period may be assigned as
an operation
index for the pump. In this embodiment, the pump may be assigned an operation
index from
0 to 49, but larger or smaller index ranges may be used. As an example, the
number of
entries in the lookup table and the range of those entries can be widened or
narrowed
depending upon the amount of variation in pump rates, across pumps and/or
voltages.
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In another aspect of the invention, the controller may determin.e an operation
time for
the pump to deliver a predetermined volume of liquid based on an operation
index that
represents an ability of the pump to provide a volume flow rate for a given
voltage supplied
to the pump and/or based on voltage supplied to the pump during the operation
time. In one
embodiment, the source of the operation index need not be from a calibration
operation
performed under the control of the controller, but instead the operation index
may be supplied
to the controller in any suitable way, such as by programrning the controller
with the
operation index at the time of manufacture of the system. The controller may
use the
operation index and/or voltage supplied to access a lookup table to identify a
suitable
operation time for the pump to deliver a desired predetermined volume, or may
use the
operation index and one or more algorithms to calculate the operation time. In
one
embodiment, a lookup table may include a two dimensional data set in which the
controller
may identify a suitable operation time (e.g., a volt-tic value) as one that
corresponds to the
pump's operation index and a voltage to be supplied to the pump during the
operation time.
In a further embodiment, the controller may monitor the voltage provided to
the pwnp
during operation and adjust or set the operation time as necessary depending
on the voltage.
For example, the controller may integrate the voltage provided to the pump,
and based on the
integrated voltage determine a total volume provided by the pump. (Voltage
provided to
some pumps is directly proportional to the volume flow rate of the pump, and
thus an
integrated voltage over time may be indicative of a total volume provided by
the pump.) One
or more correction factors may be used in the calculation, including the
operation index.
In another embodiment, the controller may access a lookup table and based on
the
operation index, select a "volt-tic" value or other operation time value. For
example, the
controller may access the lookup table in Figure 2 and select the volt-tic
value that
corresponds to the pump's operation index. The volt-tic value in the lookup
table may
correspond to a different volume than that desired for the pump to provide.
For example, in
one embodiment in which the pump completely fills the chamber 53 during a
calibration
period (e.g., a total volume of 24 ounces), the controller may multiply the
volt-tic value from
the lookup table by a factor to determine a volt-tic value that corresponds to
a different
volume (e.g., if the punip is to provide a volume of 6 ounces to the chamber
53, the controller
may multiply the volt-tic value obtained from the lookup table by 6/24).
Alternately, the
controller may maintain another lookup table that is specific to the volume to
be delivered by
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the pump, such that the controller may access and use the volt-tic value
corresponding to the
pump's operation index without using a volume correction factor or other
operation. This
volt-tic value may then be used to operate the pump, e.g., the controller may
sample the
voltage provided to the pump during the operation time in much the same way as
described
above for a calibration operation, and decrement the operation time volt-tic
value by the
voltage measurement made at each interval. When the volt-tic value is
decremented to "0",
the pump may be stopped.
While the invention has been described in conjunction with specific
embodiments
thereof, it is evident that many alternatives, modifications, and variations
will be apparent to
those skilled in the art. Accordingly, embodiments of the invention as set
forth herein are
intended to be illustrative, not limiting. Various changes may be made without
departing
from the spirit and scope of the invention.
What is claimed is:
