Note: Descriptions are shown in the official language in which they were submitted.
The invention relates to the control of a suction milking machine,
more especially to a device designed to terminate the suction
operation of the teat cups upon cessation of milk flow from the udder.
The device is further designed to indicate, either optically or
acoustically, whether the stoppage of the milk flow is due to an
empty udder or due to external causes.
It is a well kno~n fact that a milking machine must stop the pu~sations
in the teat cups as soon as the milk starts to flow out of the teats in
a trickle only, a sign that the udder is empty. Further milking will
cause irritation of the teat with subsequent inflammation which may
lead to infection of the udder and to general diseases. This problem
has been tackled in many ways, and nowadays all but the most primitive
machines are equipped with automaic stopping devices which are
monitored by the cessation of the full stream of milk from the udder
to the container and its replacement by a thin trickle. The known
devices are, wi-th~ut e~ception, built on the principle of a chamber
containing a float, electrodes or other means for monitoring the
pulsator acting on the teat cups, this chamber is positioned in the
line between the teat cups and the collecting vessel and is provided
in its bottom portion with an outlet nozzle of a very small diameter,
and with a main outflow opening of a large diameter a few centimeters
above this nozzle~ As long as a full stream of milk passes through
this chamber the liquid level therein is sufficiently high so that
the major part of the milk leaves the chamber through its high-
positioned main outflow opening, and only a small part through thenarrow nozzle. The high liquid level acts on the monitoring means
in a manner so as to keep the pulsator in motion. As soon as the
udder is nearly empty, milk flows out in a small batches and the
liquid level in the chamber sinks, since now the narrow nozzle is
sufficient to permit the passage of all the milk pumped out. This
causes the float to sink or the electrodes to stop passing a current,
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whereby the pulsator operation is stopped and the teat cups
are automatically dropped off the udder, without the assis-
tance of human hands.
Although these devices, in whate~er form they may be desig-
nated, operate quite satisfactorily while new, they are soon
clogged by fatty matter or mineral sediments contained in
the milk and many failures have been experienced. Partly
clogging will also cause wrong timing, i.e. later stopping
of the pulsator than initially intended.
~ It is therefore an object of an aspect of the present
invention to do away with control equipment dependent on
throttling of the milk flow by a narrow nozæle and to
provide a control device designed on a free flow of the milk
through a wide pipe or tube. It is an object of an aspect
lS of the invention to provide a device which will operate
independently of sedimentation on the wall of this tube or
pipe as well as independently of the fat contents of the
milk.
~topping of the milking operation alone is, however, not
advisable i~ the milk flow has stopped before the udder is
empty; several reasons may be responsible for a premature
stoppage, the most frequent being the accidental strip-
ping of the teat cups from the udder, either due to a
quick movement of the cow or to external causes. Another
cause for premalure stoppage may be the holding-back by
a frightened co~i; still another reason for early stopping
may be reduced milk yield of the animal~ either due to a
disease or to the end of the lactation period of a cow,
i.e. 9-10 months after calving.
It should be noted that incomplete milking, leaving milk
in the cow's udder, by accidental interruption o the
operation, will cause pains and may cause inflammation as
well as diminished milk yield. On the other hand,
reduced milk yield requires either treating of the diseased
animal or release of a cow into the pasture when she is at
the end of lactation.
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In a milking parlour where a large number of cows are milk-
ed simultaneously it is very important that the dairyman
becomes immediately aware of the cause of the cessation of
the milking operation, the more as the teat cups fall off
the udder as soon as the suction operation stops, and as
they are generally pulled up to the ceiling by a vacuum-
operated lifting device, and there is no way of telling
whether the cow is fully milked, whether she withholds the
milk for on~ of the above reasons, or whether her lactation
period is nearing its end.
For this reason it is an object of an aspect of the present
invention to provide the control device with means for indi-
cating, by optical or acoustical means, the different
~auses of the cessation of the milking operation: one kind
of signal serving to indicate normal stopping, before the
udder is sucked completely empty; ano:her kind of signal
indicating that the teat cups were forcibly removed ~efore
the actual end of the milking; and still another signal
indicating that the milking operation was shorter than the
minimum milking time of a healthy cow - which is about two
minutes or more -, i.e. that the milk flow from the udder
has stopped at an interval of less than two minutes after
starting.
An aspect of this invention is as follows:
A control apparatus for a milking machine which
latter is provided with teat cups operated by an electric
pulsator, a milk collecting vessel kept at sub-pressure,
a pipeline therehetween through which all of the milk
from said teat cups flows to said vessel, comprising in
combination
a tube of a non-conductive material inserted
into the pipe line connecting said teat cups to said milk
collecting vessel, said pipe line and said tube being -;
of sufficiently wide dimensions to carry the milk as
pulses of milk flowing in separated portions passing
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through said line and said tube at the rate of the pulsator
pulses,
a coil of~wire windings surrounding said tube
on its outside,
an electronic system including means for applying
a high-frequency voltage to said coil, means for detecting
the varying amplitude high frequency output signal from
said coil indicative of the varying conductivity of the
coil interior space due to the milk passing therethrough
in pulses, and means for comparing saicL output signal
with a predetermined voltage corresponding to a permissible
minimum flow o milk, the system being adapted to interrupt
the operation of said electric pulsator, as soon as the
output signal reaches the value of said predetermined
voltage.
Figure l illustrates the arrangement of a controlling
and indicating device in the piping of a conventional
suction milki~g machine, and
Figure 2 is a block diagram of an electronic circuit adapted
to terminate the pulsator operation and to produce diiferent
signals in accordance with the nature of the milking opera-
tion's end.
Before describing the working of the control and indicating
device according to the invention and to enable ull under-
standing of its design, a short description of a conven-
tional milking machine is being given in the following
with the aid of Figure 1 of the accompanying schematic draw-
ing. Herein two teats l, l' of an udder (out of four) are
shown, each of which has a teat cup 2, 2' attached to it
by subpressure maintained in the system by a central vacuum
pump (not shown). Each teat cup comprises a solid cylin-
drical housing and concentric therewith a cylindrical and
resilient membrane which form an annular inflatable space
3,3' therebetween. The teat cups are connected, by means of flexible
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hoses 4, 4' and 5, to an electric pulsator 6 which causes
pressure pulses in the annular spaces 3, 3' by alternately
connecting them to a central line 14 which is kept at sub-
pressu~e by the aforementioned vacuum pump~ and to the at-
mosphere; hereby the me~branes are alternately pressedagainst the teat and released, the inner space of the
teat cup being kept permanently at sub-pressure through the
milk lines 7, 7' and 8, and through a closed milk collector
vessel 8 connected to the central line 14 by a line 13.
The action simulates manual milking whereby the milk flows
out of the udder through the teats into the teat cups and
is sucked out from these through the milk lines into the
collector vessel 8. The pulsator is usually built to
connect simultaneously all four teats to the sub-pressure
and then to the atmosphere, or it actuates alternately two
cups on and two cups off. Suitable milking pulses vary
from 25 to 120 per minute, a common average being 60 pulses
per minute which would - in a 2/2 arrangement, pump 120
portions per minute. A control apparatus (ll~ according
to the invention is shown to be inser-tedinto the milk line;
this will be described further on.
The milk travels through the milk line in portions at a
rate determined by the pulsator frequency, interrupted by
zero supply intervals. A maximum rate of 66 cm3~s would be an
excellent yield for a cow. This maximum volume drops
gradually to a minimum of 4.75 cm3/s when a milking process
should be stopped to avoid damage to the udder.
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These pulsating flow conditions are being utilized
in the control device according to the invention, by
comparing the pulse intensity of the minimum portion
- at which the pulsator is required to stop operating
with the pulse inten~ity during normal milking opera-
tion.
The controlling and indicating device for a
conventional milking machine comprises a tube of a
non-conducting material, such as glass or plastics,
which is inserted into the piping conducting milk
from the teat cups to a milk container, this tube
being of a sufficiently large diameter so as to carry
the milk in discreteJ separated portions as dictated
by the rate
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of the electric pulsator operatj~ng the teat cups. A coil of wire
windings surrounds the tube and is connected to a radio frequency
oscillator. The coil ou-tput varies in accordance with the change
of conductivity in the tube caused by the milk portions passing
therethrough and consists of pulses of wildly varying length and
intensity depending on the irregular flow of milk through the tube
in portions of various length and veloci-ty. This output is smoothed
to a d-c voltage in an electronic circuit which comprises means for
rectifying, amplifying, filtering, zero level clamping and
demodulating the pulses, thus obtaining resultant voltage that is
proportional to the milk flow at every moment. This voltage is
compared, in a comparator unit, with a reference voltage which
corresponds to a predetermined permissible minimum flow of milk,
demanding cessation of the milking operation. As soon as the
resultant voltage is equal or lower than the reference voltage, the
comparator output serves to interrupt the operation of the electric
pulsator and to produce a signal, warning the attendant of the end
of the milking operation of the specific cow. Additional and
optional electronic circuitry is adapted to produce three specific
kinds of signals, each one indicating one of the three causes of
stoppage of milk flow through the tube. These signals may be optical
or acoustical, either in the form of continuous or interrupted light
flashes or humming sounds, or the indication may be by three
different coloured lamps, by three differently -tuned loudspeakers,
or by visual display, all of these methods being known to the art.
Before entering into the nature of the indicating device, it is
important to understand the various conditions of the milk flow in
the milking machine at the end of the operation :-
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1. Sudden removal of the teat cups does not stop the passage of n~lk
portions through the above tube at once, owing to the length of piping,
but there will be always a few last portions passing through the tube
moved by the suction pressure o:f the machine, before the pipe is
completely empty. In contradistinction to the regular ending of the
milking process wherein the size of the milk portions passing through
the tube decreases gradually, the milk portions after acc;dental
removal of the teat cups remain of the same large size until the end,
when they stop coming at all. However, since ~he cow is a living
organism, it may happen that, with a conventional milking machine
working at a frequence of 120 pulsations per minute, milk portions -
especially near the end of the operation - may p ass through the
piping and through the indicating tube at greater intervals, even up
to 10 seconds, and may then return to a shorter frequency.
2. Normal milking of a healthy cow in lactation lasts ~or a minimum of
two minutes; and in case the milking operation lasts for less than
2 minutes, this ls a sure sign that the cow is either at the end of
her lactation period, or that she is diseased, or that she, for some
reason or other, withholds her milk in her udder.
These facts are being employed to indicate either of the three causes for
s toppage of the elec~ric pulsator; for the purpose of terminating the
pulsator action and to indicate the cause of the end of the nilk ~low an
operation and indicating circuit is provided which is adapted to be
triggered either by the comparator output or by the pulses created in the
coil by the passing milk portions. The operation circuit is preferably
connected to the respecti~e input and output side of the comparator by ~wo
parallel circuits, each circuit comprising a timer switch (hereinafter
called "timer" for short~ which is set-to delay the inrpulses from reachin~
the operation circuit by a pre~etermined interval. The two timers are
interconnected, and the first timer to reach the end of its set time
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interval triggers the operation circuit to the efect of stopping the
pulsator action, however each timer produces a diferent visual or acoustical
sign with a view to in~orm the-attendant o-f the normal course, or of a sudden
interruption, of the milking operation. The circuit connecting the operation
circuit to the comparator OlltpUt is provided with a timer A which is set to
an interval slightly longer than the interval of a second timer tB) in the
parallel circuit. A second comparator ~II) s~pplied with a low reerence
~oltage, is provided in the circuit connecting the operation circuit to the
input side of the main comparator (hereinater called Comparator I) and
p ermits only pulse of a certain magnitude to reach the timer B and to reset
it every time, i.e. at the pulsator frequency. This timer B transmits a
pulse to the operation circuit only after having run through its complete
set interval which is preferably 14 seconds, i.e. a~ter the mîlk flow has
practically stopped reaching the tube.
Both timers, A and B, are set to a longer interval than ten seconds,
preerably between 14 and 16 seconds, to make allowance or the last, widely
spaced milk portions arrivingj the interval of the timer A being a few
s econds longer than that of timer B. A third timer ~C) is placed in a
circuit connecting the output o timer A with the operation circuit. This
timer is set to an interval of less than two minutes and is adapted to
issue a signal to the operation circuit to the efect that the milking
operation was stopped at a shorter time than normal.
The operation circuit is furthermore adapted to trigger rinsing and/or
desin~ecting operations o the milk passages.
~le operation of the device is as follows: With normal ending o the
milking operation, i.e. with the milk flow decreasing gradually, time A
is reset as soon as the comparator output starts, timer B having been
constantly reset by the pulses right rom the beginning of the operation.
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This timer (B) is adapted to be reset only by a pulse of a
predetermined intensity, as determined by the abovementioned
comparator II which is fed a much lower reference voltage than
comparator I; therefore, with decreasing milk flow, this timer (B)
will be reset a few times by the last pulses passing through the
tube. It will, accordingly, stop later than timer A which will
transmit -the comparator output pulse to the operation circuit after
16 seconds, with the result that the pulsator action is stopped
and, simultaneously, a visual or optical sign is given, indicating
a NORMAL run.
In the case that the milking operation was stopped shor-t off the
minimum time of 2 minutes, the same signal is transmitted to the
operation circuit by -timer A, but at the same time the timer C
received an impulse from this timer (A) before having r~m through
- 15 its interval. The timer C, in its turn, is adapted -to produce a
signal to the operation circuit to the effect that it gives a SHORT
sign instead of the NO~MAL sign.
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The third possibility that the tea-t cups have been inadvertently
removed, will reset the timer B which will continue to receive strong
pulses by the large milk portions still passing through the tube,
since these were moving along the piping at the moment the cups fell
off. ~ith the rest of the milk passing through the tlibe both timers,
A and B, will be reset at the same moment and since timer A has a
longer interval than timer B, the latter will be the first to actuate
the operation circuit, causing the pulsator to be stopped c~nd a sign
"OFF"' to be produced, warning the at-tendant.
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With reference -to Figure 1 of the drawing which has been partly
described in the foregoing, the con-trol device consists of a tube 9
of a non-conductive material such as glass or a plastic material
which is inserted into the piping conducting milk from the teat cups
to a container and is surrounded by coil windings 10 of an insulated
wire. A R-F oscillator connected to the coil terminals applies
thereto a voltage of high frequency. The milk flowing in pulses
through the tube and the coil interior causes a pulsating change of
conductivity therein, which results in a varying coil induction and
an output wave of changing amplitude as a function of the milk
portlons passing through.
This signal is passed through an electronic analysing system and is
compared with a standard pre-selected voltage which corresponds to the
permissible mimimum milk flow. As soon as this minimum value is
reachecl an output signal stops the pulsator 6 through an electric
line 16 and prc~uces a warning light 15.
~The dimensions of the tuke and coil as well as the frequency may vary
over a large range, but an apparatus built to the following
dimensions has proved itself satisfactory in all respects. The tube
was made of "Perspex" and had an inner diameter of 16 mm and a length
of 250 mm. The coil wound around the outer tube diameter of 19.8 mm
had a lenc~th of 85 mm, about 75 windings of a 1.0 mm wire. m e
oscillator fre~uency was between 1 and 7 MHz.
Nevertheless, taking into account available space and electric
conditions, it is proposed that the coil may have as little as 4
win~ings and a length of 5 mm or as many as 1000 windings at a
length of 200 mm,while the
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frequency may vary between 250 kHz and 20 ~lz. The minimum diameter o~
the tube may be 8 mrn and the maximum 40 mrn. ~le pulsator frequency may
likewise vary between 25 and 120 milking pulses per minute.
Any non-conducting material that is not detrimental to milk may be used
in the manufacture of ~he tube such as e.g. glass, provided it is wide
enough to have the milk portions separated from each other, a continuous
flow giving no signal at all.
Figure 2 shows an electronic circuit adapted to terminate tlle pulsator
action and to procluce three different kinds of signals. l~e Figure shows
the tube 9 of a non-conducting material surrounded by a wire coil 10.
A radio frequency oscillator is connected to the coil, and the resulting
changing pulses are rectified, amplified, filtered and demodulated, before
being fed into a comparator ~ which issues a signal as 500n as the input
voltage reaches the value of the reference voltage. The signal is fed into
an output and operation circuit through a timer A which is set, in the
present case~ to an interval of 16 seconds, and produces a NO~lAL signal.
A second timer B, set to a shorter interval (14 seconds) is triggered by
pulses before the comparator I, the connection being via a second
comparator II which is supplied with~a reference voltage of low ma~nitude,
preventing the timer to be triggered by very weak pulses. The timer B is
likewise connected to the output and operation circuit~ besides of feeding
its output into timer A and into a third ~imer C. Likewise the output of
timer A is fed into timer B. The timer C is set *o an interval of about
100 seconds and its output ~ed into the operation circuit. This circuit
is provided with three lamps (in the present case) only one lamp each being
lighted at the end of the milking operation dependent on the action of the
difEerent timers. The circuit further operates a switch 20 when actuated
by either timer ~ or B. Another operation circuit causes rinsing and/or
disinfecting of the milking machine to be initiated after the end oE the
milking process.
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The operation of the circuitry will be described again lYith reerence to
Figure 2: rne timer B is reset by each pulse issued by the zero level clanper,
since its interval is much larger than the pulsator freqllency, however the
timer C runs off after 100 seconds, if the milking operation lasts longer
tilan that, i.e. is of normal length. As soon as the milk flow decreases
below the stipulated minimum level, the timer A is actuated and runs down
in 16 seconds~
The weak pulses Yhich have triggered the con~arator, are still strong enough
to reset the timer B, as the reference voltage oi` its con~arator II is much
lower than that of con~arator I. For this reason timer A will run down
before timer B and will trigger the operation circuit, to the e~ect of
stopping the pulsator action c~nd to light a "NORMAL" sign. In case the
milk Elow has decreased below standard while the timer C is still running,
it will receive a sic~nal fro~ the timer A, and will cause a lamp SHORT to
be lighted, while the pulsator operation is being terminated as before.
However, in case the milking is suddenly interl~pted while the milk flow
is still high, the timer B will be actuated by the last, large n~lk portions
remaining in the long pipe line, and both timers will be reeet
simultaneously when the last portion has passed through the tube. Now
timer B will be the first to actuate the operation circuit, cut the pulsator
action and give an "OFF" sign, denoting that the cups have dropped ofE by
accident.
It is reiterated that any kind of signal can be given, either visual or
acoustical, and that the circuitry may be changed, as long as the principle
of the three timers is maintained.
The advantage of giving ready information to the dairyman is evident, and
since all components of the electronic circuit are standard and commercially
availableJ the cost of a device of this kind will be compensated in a very
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s hort time by en~bling the personnel to attend in time to cows that require
treatmellt or removal from the millcing parlour.
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