GB2090431A - A control device for a milking machine - Google Patents

Abstract

In a suction milking machine the milk, in discrete portions, is passed through a non-conductive tube 9 on which is wound a coil 10 connected to a high-frequency oscillator. The coil output varies in dependence on the presence of milk portions and is fed direct to a comparator II, and demodulated, to obtain a voltage proportional to the instantaneous milk flow; to a comparator I. An operation circuit switches off a pulsator of the machine through a switch 20 and triggers rinsing and/or disinfecting operation, when 1) in normal operation milk flow decreases gradually and a timer A is reset before a timer B (a short indication is given when the timer A is reset before a minimum milking period timer C, and 2) a teat-cup has been inadvertently removed and timer B is reset before timer A and an off indication given. <IMAGE>

Description

SPECIFICATION A controlling and indicating device for a milking machine 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 known fact that a milking machine must stop the pulsations 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 automatic 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, without exception, 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 centimetres 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 highpositioned main outflow opening, and only a small part through the narrow 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 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, whereby the pulsator operation is stopped and the teat cups are automatically dropped off the udder, without the assistance of human hands.

Although these devices, in whatever form they may be designated, 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 intiailly intended.

It is therefore the object of the present invention to do away with control equipment dependent on throttling of the milk flow by a narrow nozzle and to provide a control device designed on a free flow of the milk through a wide pipe or tube. It is another object 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.

Stopping of the milking operation alone is, however, not advisable if 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 stripping of the teat cups from the udder, either due to a quick movement of the cow or to external causes. Another cause for premature stoppage may be the holding-back by a frightened cow; 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 of the operation, will cause pains and may cause inflammation as well as diminished milkyield. 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.

In a milking parlour where a large number of cows are milked 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 one of the above reasons, or whether her lactation period is nearing its end.

For this reason it becomes another, very important object of the present invention to provide the control device with means for indicating, by optical or acoustical means, the different causes of the cessation of the milking operation: one kind of signal serving to indicate normal stopping, before the udder is sucked completely empty; another kind of signal indicating that the teat cups were forcibly removed before 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 had stopped at an interval of less than 2 minutes after starting.

Before describing the working of the control and indicating device according to the invention and to enable full understanding of its design, a short description of a conventional milking machine is being given in the following with the aid of Figure 1 of the accompanying schematic drawing. Herein two teats 1, 1' 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 cylindrical 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 hoses 4, 4' and 5, to an electric pulsator 6 which causes pressure pulses in the annular spaces 3, 3' by alternateiy connecting them to a central line 14 which is kep at subpressure by the aforementioned vacuum pump, and to the atmosphere; hereby the membranes are alternately pressed against 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 connected to the central line 14 by a line 13.

The action simulates manual milking whereby the milk fiows 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 (11) according to the invention is shown to be inserted into 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 the milking process should be stopped to avoid damage to the udder.

These pulsating flow conditions are being utilised 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 intensity during normal milking operation.

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 discrete, separated portions as dictated by the rate of the electric pulsator operating the teat cups. A coil of wire windings surrounds the tube and is connected to a radio frequency oscillator. The coil output 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 velocity.This output is smoothed to a d-cvoltage in an electronic circuit which comprises means for rectifying, amplifying, filtering, zero level clamping and demodulating the pulses, thus obtaining a 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 attendentofthe end of the milking operation of the specific cow. This device is described in Patent Specification No. 55360.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: 1. Sudden removal of the teat cups does not stop the passage of milk 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 of 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 accidental removal of the teat cups remain of the same large size until the end, when they stop coming at all.However, since the 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 pass through the piping and through the indicating tube at greater intervals, even up to 10 seconds, and maythen return to a shorter frequency.

2. Normal milking of a healthy cow in lactation lasts for a minimum of two minutes; and in case the milking operation lasts for less than 2 minutes, this is 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 stoppage of the electric pulsator; for the purpose ofterminating the pulsator action and to indicate the cause of the end of the milk flow 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 respective input and output side of the comparator by two parallel circuits, each circuit comprising a timer switch (hereinafter called "timer" for short) which is set to delay the impulses from reaching the operation circuit by a predetermined interval.The two timers are interconnected, and the first timer to reach the end of its set time interval triggers the operation circuit to the effect of stopping the pulsator action, however each timer produces a different visual or acoustical sign with a view to inform the attendant of the normal course, or of a sudden interruption, of the milking operation. The circuit connecting the operation circuit to the comparator output is provided with a timer A which is set to an interval slightly longer than the interval of a second timer (B) in the parallel circuit. A second comparator (11) supplied with a low reference voltage, is provided in the circuit connecting the operation circuit to the input side of the main comparator (hereinafter called Comparator I) and permits only pulses 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. after the milkflow has practically stopped reaching the tube.

Both timers, A and B, are set to a longer interval than ten seconds, preferably between 14 and 16 seconds, to make allowance for the last, widely spaced milk portions arriving, the interval of the timer A being a few seconds longer than that of timer B. Athird timer (C) is placed in a circuit connecting the output of 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 effect that the milking operation was stopped at a shorter time than normal.

The operation circuit is furthermore adapted to trigger rinsing and/or desinfecting operations of the milk passages.

The operation of the device is as follows: With normal ending of the milking operation, i.e. with the milk flow decreasing gradually, timer A is reset as soon as the comparator output starts, timer B having been constantly reset by the pulses right from the beginning of the operation. This timer (B) is adapted to be reset only by a pulse of a predetermined intensity, as determined by the above-mentioned 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 short of 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 run through 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 NORMAL sign.

The third possibility that the teat 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. With the rest of the milk passing through the tube 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 and a sign "OFF" to be produced, warning the attendant.

In the accompanying drawings which iilustrate, by way of example, two embodiments of the controlling and indicating device, Figure 1 illustrates the arrangement of the device in the piping of a conventional suction milking machine (as described in Patent Application No. 55360).

Figure 2 is a block diagram of an electronic circuit adapted to terminate the pulsator operation and to produce different signals in accordance with the nature of the milking operation's end.

With reference to Figure 1 of the drawings which has been partly described in the foregoing, the control device consists of a tube 9 of a nonconductive 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.

An 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 portions passing through.

This signal is passed through an electronic analysing system and is compared with a standard preselected voltage which corresponds to the permissible minimum milk flow. As soon as this minimum value is reached an output signal stops the pulsator 6 through an electronic line 16 and produces a warning light 15.

The dimensions of the tube and coil as well as the frequency may very 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 length of 85 mm, about 75 windings of a 1.0 mm wire. The oscillator frequency 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 windings and a length of 5 mm or as many as 1000 windings at a length of 200 mm, while the frequency may vary between 250 kHz and 10 MHz. The minimum diameter of the tube may be 8 mm and the maximum 40 mm. The pulsator frequency may likewise vary between 25 and 120 milking pulses per minute.

Any non-conducting material that is not deterimental to milk may be used in the manufacture of the 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 the pulsator action and to produce three different kinds of signals. The 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 I which issues a signal as soon 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 NORMAL 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 magnitude, 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 timer C. Likewise the output of timer A is fed into timer B. The timer C is set to an interval of about 100 seconds and its output fed 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 different timers. The circuit further operates a switch 20 when actuated by either timer A or B.Another operation circuit causes rinsing and/or disinfecting of the milking machine to be initiated after the end of the milking process.

The operation of the circuitry will be described again with reference to Figure 2: The timer B is reset by each pulse issued by the zero level damper, since its interval is much larger than the pulsatorfrequency, however the timer C runs off later 100 seconds, if the milking operation lasts longer than 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 which have triggered the comparator, are still strong enough to reset the timer B, as the reference voltage of its comparator II is much lower than that of comparator I. For this reason timer Awill run down before timer B and will trigger the operation circuit, to the effect of stopping the pulsator action and to light a "NORMAL" sign. In case the milk flow has decreased below standard while the timer C is still running, it will receive a signal from 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 interrupted while the milk flow is still high, the timber B will be actuated by the last, large milk portions remaining in the long pipe line, and both timers will be reset 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 off 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 available, the cost of a device of this kind will be compensated in a very short time by enabling the personnel to attend in time to cows that require treatment or removal from the milking parlour.

Claims (6)

1. Acontrol devicefora milking machine which is provided with teat cups operated by an electronic pulsator and with a milk collecting vessel kept at sub-pressure, comprising in combination a tube of a non-conducting 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 in separated portions passing 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 applying a high-frequency voltage to said coil, the system being provided with a first comparator having an input voltage in the form of the output wave signal of said coil created by the varying conductivity of the coil interior space due to the milk passing therethrough in discrete portions, and producing an output signal upon the input voltage decreasing to a reference voltage corresponding to a permissible minimum flow of milk through said tube, an operation circuit adapted to cause the termination of said electric pulsator action upon being triggered either by the output voltage of said first comparator via a first circuit containing a first timer switch, or by the output wave signal of said coil via a second circuit containing a second timer switch and a second comparator, said two timer switches being set to time intervals larger than 10 seconds, whereby the interval of said first timer switch is somewhat longerthan that of said second timer switch; said second comparator being adapted to pass only pulses of a voltage higher than a reference voltage which latter is considerably lowerthan said reference voltage fed to said first comparator; said operation circuit being further adapted to produce a visual or acoustic sign denoting a normal course of milking, upon being first triggered by said first comparator output voltage, and to produce a visual or acoustic sign denoting the removal of said teat cups from the udder before the termination of the milking process, upon being first triggered by the output wave signal of said coil via said second circuit.

2. A control device according to claim 1,com- prising a third timer switch set to an interval of less than two minutes placed in a circuit between the output of said first timer switch and said operation circuit, adapted to cause said operation circuit to produce a visual or acoustic signal denoting the natural termination of the milking process within a period of less than two minutes, upon receiving a signal from said first timer switch before termination of the time interval of said third timer switch.

3. A control device according to claim 1 or 2, comprising a tube made of glass.

4. A control device according to claim 1 or 2, comprising a tube made of a plastic material.

5. A control device according to any preceding claim, wherein the frequency used is between 1 and 7 MHz.

6. A control device according to claim 1, substantially as herein described with reference to the accompanying drawings.