Note: Descriptions are shown in the official language in which they were submitted.
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Milking device
The present invention relates to a milking device for milking a dairy animal,
which device is provided with at least one milking cup having a teat space and
a pulsation
space, a control device for controlling the milking device, a vacuum device
for applying an
underpressure, a pulsation device having an openable and closable first
pressure
connection which is controllable by the control device and runs from the
pulsation space to
the vacuum device, and an openable and closable second pressure connection
which is
controllable by the control device and runs from the pulsation space to a
source of a
second pressure which is higher than said underpressure, which source in
particular
comprises the ambient, wherein the pulsation device is configured to apply, in
a way which
is controllable by the control device, a pressure which varies in pulses in
the pulsation
space by means of specifically opening and/or closing the first and/or the
second pressure
connection, and a pressure-determining device configured to determine a
pressure in the
pulsation space and comprising a pressure sensor, and a third pressure
connection which
runs from the pulsation space to the pressure sensor, wherein the control
device is
configured to regulate the pulsation device on the basis of the determined
pressure.
Milking devices of this type are known, both in their conventional form and in
the robot configuration. Measuring the pressure in the pulsation space may
serve to
monitor or adjust the pulsation in the device.
A problem with the known devices is that these only have a limited service
life, more particularly that the pressure-determining device only provides a
reliable
pressure signal for a limited time. This means that a lot of time and money is
associated
with repairing or replacing the pressure-determining device.
It is an object of the present invention to at least partially eliminate said
problem.
The invention achieves this object by means of a milking device according to
Claim 1, in particular a milking device for milking a dairy animal and
provided with:
- at least one milking cup having a teat space and a pulsation space,
- a control device for controlling the milking device,
- a vacuum device for applying an underpressure,
- a pulsation device having an openable and closable first pressure
connection which
is controllable by the control device and runs from the pulsation space to the
vacuum
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device, and an openable and closable second pressure connection which is
controllable by
the control device and runs from the pulsation space to a source of a second
pressure
which is higher than said underpressure, which source in particular comprises
the ambient,
wherein the pulsation device is configured to apply, in a way which is
controllable by the
control device, a pressure which varies in pulses in the pulsation space by
means of
specifically opening and/or closing the first and/or the second pressure
connection,
and
a pressure-determining device configured to determine a pressure in the
pulsation
space and comprising a pressure sensor, and a third pressure connection which
runs from
the pulsation space to the pressure sensor, wherein the control device is
configured to
regulate the pulsation device on the basis of the determined pressure,
wherein furthermore a sensor valve device which is controllable by the control
device is
provided in the third pressure connection, which sensor valve device is
configured to
controllably open and close the third pressure connection.
The insight behind the invention is that the pressure sensor in milking
devices
is exposed to an underpressure for approximately half of each pulse, that such
pulses are
generated in the device for a large part of the time each day and that the
pressure sensor
is thus in total exposed to such an underpressure for a large part of the day,
moreover that
this pressure changes very frequently, and that the load on the pressure
sensor is
therefore very large. However, the pressure hardly appears to change from
pulse to pulse,
and certainly not so quickly that every pulse has to be measured. The idea is
therefore to
measure only during a limited period of time and not to expose the pressure
sensor to the
(alternating) underpressure for the remaining time. The service life of the
pressure sensor
can thus increase accordingly. In addition, the problems with the service life
of the pressure
sensor meant that, in the prior art, the pressure sensor often consisted
merely of an
external pressure sensor which was only connected and used during maintenance
of the
milking device. In that case, there was no protection for the sensor in the
form of the
sensor valve device, and certainly no sensor valve device controllable by the
control device
and/or permanently integrated. As a result, milking devices according to the
prior art could
therefore not, or at least to a far lesser extent, control the pulsator on the
basis of
measured pressure. The present invention makes it possible to implement a
pressure
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sensor in a milking device in order to thus have pressure values available for
each milking
operation in order to control the milking process.
It should be noted here that it is known per se from the prior art relating to
pressure sensors to shield a pressure sensor from the space in which the
pressure must
be measured in some cases, but this is only done if there is an overpressure
wave or if a
pressure value which differs (too) greatly from the customary pressure values
is otherwise
suspected or detected, which could damage the pressure sensor. In that case it
is a safety
valve. By contrast, the insight in the present invention is that the sensor
valve device is
closable by the control device in such a way that the pressure connection is
closed in the
case of a customary (under)pressure and not only in the case of a certain
minimum
overpressure. That is why, in this case, the closing does not occur
automatically in
response to an overpressure (which after all, in principle, will not occur),
but does occur
under the control of the control device and at a pressure with a value in the
range from and
including said underpressure up to and including said second pressure, or at a
usual
operating pressure. It should be noted that the precise value at which the
control device
closes the third pressure connection is not important and may vary for each
opening and
closing action. It is merely important that the opening and closing occurs at
a usual
operating pressure and not at a (dangerous) overpressure or such abnormal
operating
pressure. It should furthermore be noted that, if the sensor valve device were
to close
automatically at a usual operating pressure, the device according to the
invention could not
even work. The known valve device, as such, is therefore unusable in the
present invention
for the achieved object. It is of course not impossible to additionally
integrate the known
device mentioned above in order to protect the sensor valve device against
possible
overpressures, but the object of the invention is not achieved using this
device alone.
Within the context of the present invention, the control device is configured
to
control the milking device and thus also parts thereof, such as the pulsation
device. In this
case, the control device may be distributed, in other words there are a
plurality of modules
which optionally function independently of one another. In that case, the
control device
should be considered to be the entirety of all components which (individually
or together)
control part of the milking device.
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The source for the second pressure may in principle be any source which
supplies a pressure which is sufficient for folding the pulsation space, in
particular folding
the lining of the milking cup. Such a second pressure may, for example, be a
slight
underpressure, or even an overpressure. In particular, however, the source for
the second
pressure is the surroundings, so that the second pressure is equal to the
ambient pressure.
Such a source is of course always available and provides an adequately defined
pressure.
However, separate sources may have an advantage since they are more readily
controllable and offer even more accurately defined pressure.
According to the invention, the pressure-determining device is configured to
to determine the pressure in the pulsation space, wherein "determine"
comprises the direct
measurement and also the indirect measurement of the pressure. In this case it
should be
noted, however, that there must be a pressure connection when determining the
pressure,
in other words a flow connection, wherein air can flow between the pulsation
space and the
pressure sensor. After all, the resolved problem will predominantly occur if
there is such a
pressure connection to the pressure sensor.
It should also be noted here that the principle of the invention, namely, in
the
case of a substantially continuous alternation of the pressure to be measured,
only
exposing the pressure sensor to said pressure for a limited period of time, is
also
applicable to other pressure measurement devices. An example is a milking
device having
a pressure sensor configured to measure a pressure which varies in a pulsed
manner, for
example in the teat space, such as in the space between the place where the
lining folds
shut and the udder, which milking device is provided with a pressure
connection between
said space and the pressure sensor, wherein a sensor valve device which is
controllable,
in particular by the control device of the milking device, is also provided in
the pressure
connection, which sensor valve device is configured to controllably open and
close the
pressure connection. The advantages in this case are identical to those
mentioned above.
Usually, however, this sensor is also exposed to milk, directly or indirectly,
and there is a
permanent barrier in the pressure connection for reasons of hygiene. A milking
device
having a pressure sensor for the vacuum source (vacuum pump), wherein the
pressure
sensor with a pressure connection is operatively connected to the vacuum
source, and
wherein a sensor valve device which is controllable by the control device is
also provided in
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the pressure connection, which sensor valve device is configured for
controllably opening
and closing the pressure connection, also, for example, provides the
advantages according
to the invention. The latter milking device, however, is far less exposed to
varying
pressures.
5
Particular embodiments of the invention are described in the dependent
claims, and in the following part of the description. In particular, the
controllable sensor
valve device has a controllably closable fourth pressure connection to ambient
pressure. In
embodiments, the control device is configured to open the fourth pressure
connection
when the third pressure connection has been closed by the sensor valve device.
Ambient
pressure, in other words the ambient air, can flow to the pressure sensor via
the fourth
pressure connection to said ambient pressure in order to unload the pressure
sensor. In
particular when the third pressure connection is closed, when the pressure
sensor no
longer has to measure, opening the fourth pressure connection will very
rapidly lead to an
equalization of pressure, as a result of which the sensor may remain in the
unloaded state
until the following measurement point. However, it is also possible to operate
without such
a pressure connection to ambient pressure, for example allowing the pressure
sensor to
stop measuring when a substantially atmospheric pressure is measured,
following which
the third pressure connection is closed. Although there will always be some
leakage of
ambient air to the pressure sensor, which will also cause the pressure sensor
to be
unloaded in line with the amount of the leakage, the fourth pressure
connection is a
designed and intended connection to the surroundings, and is moreover
controllably
closable.
The pressure sensor may be an absolute sensor, in other words a sensor
which emits a signal which is dependent on the absolute pressure as measured
by the
pressure sensor. In embodiments, the pressure sensor is a differential
pressure meter, in
particular a differential pressure meter of a pressure difference between the
pressure in the
pulsation space and ambient pressure. Such a differential pressure meter may
have
advantages in terms of calibration, as ambient pressure is the most commonly
used
second pressure for pulsators.
In embodiments, the control device is configured to keep the third pressure
connection open for a predetermined time and to close the third pressure
connection at the
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end of the predetermined time. In these embodiments, measurements may be
carried out
during this predetermined time, following which the pressure sensor may rest
for the
remaining time. The predetermined time may in principle be chosen arbitrarily,
but in
practice is chosen in such a way that the measured value is able to determine
the pressure
in a sufficiently reliable manner. This time period may depend on the type of
pressure
sensor, on the degree to which pressure resonances may occur, etc. A practical
test will
simply be able to provide a suitable time. For example, the current pressure
may be
determined sufficiently accurately within 10 s. If calibration measurements
further reveal
that the maximum pressure variation is 2%/min. and the permitted margin in the
pressure is
5%, it may then be sufficient to measure for 10 s and to then allow the sensor
to rest for 2
min. 20 s. In such a case, the service life of the sensor may be extended by a
maximum of
a factor of 15. Other predetermined times and intervals are of course also
possible. In
particular, these predetermined times and intervals apply to each milking
operation, so that
the process is started from the beginning in each new milking operation. After
all, the
situation and the settings for the milking device may change for each dairy
animal.
In embodiments, the predetermined time comprises a certain time period, a
predetermined number of pulses or a time period during which a predetermined
criterion is
met. These are all possibilities for setting the "predetermined time". For
instance, it could
be desirable to measure the pressure for a predetermined minimum number of
pulses, in
order to thus obtain a sufficiently reliable and stable value.
In embodiments, the criterion comprises the measured pressure differing by
more than a predetermined amount from a desired pressure value. In other
words, the
pressure value is measured for as long as the measured pressure value differs
from the
desired pressure value by more than the predetermined amount. This is
particularly
important if the pulsation device is self-adjusting, in which cases the
settings of the
pulsation device change in order to obtain the desired pressure value. In this
case, the
pressure sensor may serve to control the pulsation device on the basis of the
measured
pressure value. More particularly, the criterion comprises said difference
being present
during a predetermined measurement period. This means that a random peak or
"spike" is
not sufficient to meet the criterion. Moreover, it will be clear that in
particular in the periods
when ambient pressure prevails in the pulsation space there will be little or
no difference
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between the measured value and the desired value. The measurement period may
therefore be accumulated from parts of successive pulses, in particular the
parts of the
pulses during which at least a minimum underpressure prevails, such as the so-
called b
phase or suction phase of a pulse, optionally combined with the a and c
phases, or the
transition phases.
In embodiments, the predetermined criterion comprises the third pressure
connection having been closed during a closure period immediately prior
thereto. This
means that no measurements were made during the preceding closure period and
that the
circumstances may therefore have changed, which could require a new
measurement. On
the basis of calibration measurements, for example, it is possible to
establish that
measurements are required at least once per fixed period, such as once per 30
s or the
like. A measurement itself may also have a certain duration, such as the above-
mentioned
minimum time period or a minimum number of pulses.
In an embodiment, the milking device according to the invention further
comprises an additional measuring device configured to measure an additional
parameter
value relating to the milking operation, for example a flow of milk, and
wherein the control
device is configured to operate the sensor valve device on the basis of the
measured
additional parameter value. In particular, the criterion comprises the at
least one additional
parameter value meeting a second criterion. These embodiments may use the
additional
measuring device to establish whether a change in the pressure in the
pulsation space is
likely. Moreover, it is possible for the milking device to be controlled on
the basis of the
measured additional parameter value, which could also lead to a changed
pressure in the
pulsation space. A flow of milk may be mentioned as an example of the
additional
parameter. A change in the flow of milk, for example, may change the setting
of the
pulsation device. For instance, at the start of a milking operation the flow
of milk must first
get up to speed, for the purpose of which the pulsation device often carries
out very rapid
and somewhat weaker pulsation. Once the flow of milk is up to speed, a main
milking
regime is initiated, in which the pulsator pulses, for example, once per
second with a high
so-called suction/rest ratio. When the flow of milk once again sinks below a
threshold at the
end of a milking operation, the pulsation device may switch to a so-called
post-milking
setting, which may comprise yet other values for the pulsation pressure and
its course over
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time. The criterion may thus comprise, for example, that the flow of milk must
be higher
than a first threshold, or must fall below a second threshold. Other
additional parameters
could of course also be used, such as an expected milking duration.
In embodiments, the milking operation is divided into a plurality of periods
having different pulsator settings, wherein the control device is configured
to open the
sensor valve device at least once during at least one of these periods, and in
particular
during each of these periods, for example for a predetermined opening time
period
selected for each period. As already described above, the settings of the
pulsation device
may change during the milking operation, for example as a function of the time
or the
measured flow of milk. Such a change in the settings may result in the
pressure in the
pulsation space changing, either in terms of absolute size or in terms of its
progress over
time. In order to obtain a reliable measurement even after such a possible
change, it may
be decided, in accordance with these embodiments, to measure at least once in
one or
more of these periods, for the purpose of which the sensor valve device is
opened. In this
case, it is possible, although not compulsory, to perform such a measurement
for a
predetermined opening time period selected for each period, such as 10 s or 10
pulses or
the like. It should be noted that the opening time period may vary for each
period.
The invention will be explained below with reference to the drawing, which
shows some non-limiting illustrative embodiments of the invention, in which
identical
reference numerals indicate identical or similar components, and in which:
- Figure 1 diagrammatically shows an embodiment of the milking device
according to the invention in a partially cut-away side view (not to scale);
- Figure 2 diagrammatically shows the interval of time of a pulsation
pressure,
and a representation of the measurement of the sensor 24; and
- Figure 3 shows three graphs one above the other of the flow of milk,
pressure and measurement, parallel in time.
Figure 1 diagrammatically describes an embodiment of the milking device
according to the invention in a partially cut-away side view (not to scale).
The milking
device as a whole is indicated by reference numeral 1, and comprises a robot
arm 2, a
milking cup 3, a pulsation device 4, a pressure-determining device 5 and a
control device
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6. Furthermore, reference numeral 7 indicates a teat of a dairy animal and 8 a
milk-flow
meter.
The robot arm 2 is configured to attach the milking cup 3 to a teat 7. For
this
purpose, the robot arm 2 comprises components which are known per se and are
not
illustrated here in more detail, such as a teat-detection device, robot-arm
actuators and a
milking-cup gripper.
The milking cup 3 comprises a sleeve 9, inside which is a flexible lining 10.
The sleeve 9 and the lining 10 enclose a pulsation space 11, and inside the
lining 10 there
is a teat space 12 for accommodating the teat 7. Underneath the milking cup 3,
the lining
10 merges into, or is at least connected to, the milk pipe 13.
The pulsation device 4 is connected to the pulsation space 11 via a first
pressure connection 14. The pulsation device 4 comprises a pulsator valve
device 15 and
a vacuum device 16 having a buffer vessel 17, a vacuum pump 18 and an air
filter 19. The
pulsation device 4 also comprises a second pressure connection 20 which is
connected to
the surroundings 21 via an air filter 19. The pulsation device 4, and in
particular the
pulsation valve device 15, is controllable by the control device 6.
The pressure-determining device 5 comprises a third pressure connection 22,
a sensor valve device 23, a sensor 24 and an (optional) fourth pressure
connection 25. The
sensor 24 is connectable to the surroundings 21 via the sensor valve device 23
controllable
by the control device 6 and the fourth pressure connection 25, provided with
an air filter 19.
The sensor 24 is also operatively connected to the control device 6 for
emitting a sensor
signal.
During use of the milking device 1, the control device 6 will operate the
robot
arm 2 in order to attach a milking cup 3 to a teat 7. It should be noted that
the robot arm 2
does not necessarily have to grip the milking cup 3 and that the milking cup 3
may also be
provided on the robot arm 2 on a milking cup holder, such as for example in
the Lely
AstronautTM system. The details thereof, such as of the robot arm, do not fall
within the
scope of the present invention and will therefore not be explained in any more
detail here.
Following attachment to the teat 7, the control device 6 will operate the
pulsation device 4 in order to vary the pressure in the pulsation space 11 in
a pulsed
manner. This causes, in a manner known per se, the lining 10 to leave the teat
space 12
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open when there is a low pressure in the pulsation space 11, as a result of
which the teat
7, which is then located in the teat space 12, is subjected to a milking
vacuum which sucks
milk out of the teat towards the milk pipe 13. The control device 6 then
controls the
pulsation device 4 in such a way that the pressure in the pulsation space 11
increases, as
5 a result of which the lining 10 will fold up and close off the teat
space, in which case the
milking vacuum no longer acts on the teat 7 but at least the lining 10 may
massage the teat
7. This principle of milking in a pulsed manner is known per se. In order to
realize the
alternating pressure in the pulsation space 11, the pulsation device 4 on the
one hand
comprises a vacuum source in the form of the vacuum device 16, and on the
other hand a
10 source of higher pressure, in this case the surroundings 21. The
pulsation valve device 15
is configured to alternately bring the first pressure connection 14 into
connection with the
vacuum device 16 and the surroundings 21.
In order to monitor the pulsation action, a pressure-determining device 5 is
provided with a sensor 24. If the sensor 24 were continuously in direct
connection with the
pulsation space 11, as is the case in the prior art, the sensor 24 would be
under alternating
pressure for a very large part of the time, for example between 1 atmosphere
and
approximately 0.5 atmosphere absolute. Moreover, the sensor 24 would in that
case be
under the low pressure for a large part of the time. Both situations, namely
alternating
pressures and the low pressure, cause ageing of the sensor 24, so that it only
has a limited
service life. With the aid of the sensor valve device 23, the sensor 24 may be
closed off
from the low pressure and/or the pressure alternations, if desired. For this
purpose, the
control device 6 may, for example, set the sensor valve device 23 in such a
way that the
sensor 24 becomes connected to the surroundings via the fourth pressure
connection 25,
with the third pressure connection 22 to the pulsation space 11 being
simultaneously
closed. In that case, the sensor device 24 is under a constant resting
pressure, in other
words atmospheric pressure.
By means of the sensor valve device 23, it is thus possible to extend the
service life of the sensor 24 by allowing the sensor to measure and be exposed
to a
(varying) underpressure only if desired. The criterion for if desired" may be
selected in
accordance with the invention, such as in a predetermined duty cycle. An
example is 10 s
measuring and 30 s rest, 10 s measuring, 30 s rest, etc. In this case, it is
assumed that the
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pulsation is sufficiently stable. This will be explained in greater detail
below with reference
to Figures 2 and 3.
In this case, the third pressure connection 22 is directly connected to the
pulsation space 11 by means of a separate pressure connection, but could also
be
connected to the pulsation space 11 via the first pressure connection 14.
However, a direct
connection which is separate from other pressure connections has the advantage
that the
pressure is measured through (by means of) a duct having a less turbulent
flow. In that
case, the pressure values measured by the pressure sensor 24 will be more
reliable.
Figure 2 diagrammatically shows the progress over time of a pressure in the
pulsation space 11, and a diagrammatic representation of the measurement of
the sensor
24. The upper part of the graph shows the absolute pressure in the pulsation
space 11,
which varies between atmospheric pressure 1 bar and a lowest pressure of
approximately
0.55 bar. The pulsations start shortly after the time to.
The lower part of the graph diagrammatically indicates the time during which
the sensor 24 is actively measuring and is therefore connected to the
pulsation space 11.
In this case, a value of 1 for the sensor S is equal to measuring the
pressure, and thus
being exposed to pressure variations and low pressure, while the value of 0
stands for not
measuring, in other words resting at atmospheric pressure.
It can be seen that the sensor only measures between the times to and t1, in
other words for approximately five pulsations. The sensor 24 does not measure
during the
time from t1 to t2, when the pulsations have already ceased and the milking
operation has
ended. It will be clear that the service life of the sensor 24 can be
drastically extended in
the case of such a measurement schedule.
Figure 3 shows three graphs one above the other which run parallel in time.
The upper part shows the course of the flow of milk as measured by the milk-
flow meter 8
in the milk pipe 13 during a milking operation. Underneath this is the
absolute pressure in
the pulsation space 11 and underneath that is the optional measurement by the
sensor 24.
The pulsation device begins pulsing at time to, in this case first of all in a
stimulation mode using rapid pulses until a time t2 when the flow of milk
exceeds a
threshold ml. At that moment, the pulsation device switches to pulsing at a
lower frequency
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and with a larger pressure difference, until time t4 when the flow of milk
falls below the
threshold m1 once again and after which the pulsation switches to pulsating at
a frequency
which is identical in principle but with a lower pressure difference. It
should be noted that
the pressure differences for the pulsation device may also remain the same in
principle,
given that a lowest vacuum which is lower will only widen the opening of the
teat space 12.
Nevertheless, in certain cases it may be more advantageous to make the
pulsation vacuum
less strong when the associated milking vacuum is set lower during the phases
between to
and t2 and following t4. In that case, a smaller pulsation vacuum, in other
words a smaller
pressure difference between pulsation space 11 and teat space 12, is
sufficient to open the
to lining 10.
It can also be seen that the sensor 24 only measures during a first time
interval T1, which runs from to to t1 and only represents part of the so-
called pre-
milking/stimulation phase. During the main milking phase which begins at time
t2, the
sensor 24 also starts measuring again, in this case for an interval T2 which
lasts until time
t3. The sensor then measures again during an interval T3 which runs from time
t4 to t5,
during the so-called post-milking phase. In all three cases, the sensor 24
thus measures
only during part of the phase in question. In this case it is once again
assumed that the
pulsation setting is adequately stable during the rest of the phase, so that a
measurement
during only part thereof is sufficiently reliable. This may all be tested in a
simple manner in
practice. If the pulsation setting of the pulsation device is not sufficiently
reliably stable, the
control device 6 may also control the pressure-determining device 5 in such a
way that
measurements are carried out once again, for example after a certain waiting
time, such as
from 30 s after the previous measuring period. It should also be noted that
the lengths of
the respective intervals T1, T2, T3 are merely indicated diagrammatically and
may have any
desired duration, such as 10 s, 15 pulsations, etc.
The situation illustrated in Figure 3 is an example in which the pressure-
determining device 5, in particular the sensor valve device 23, is controlled
on the basis of
a value of an additional parameter, in this case the flow of milk. It will be
clear that the
pressure-determining device 5 may also be controlled as a function of other
variables, such
as the expected milking time and the like.
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It will be clear to a person skilled in the art that the scope of the
invention is
not limited to the examples discussed above, but that various variations and
modifications
thereof are possible without departing from the scope of the invention as
defined in the
attached claims.
