SENSOR FOR MILKING MACHINES

Abstract: The present invention relates to a device and a method for monitoring the attachment of teat cups (9' - 9'''') to the teats (13' - 13'''') of an animal in a milking machine. The pressure in a common working fluid supply line (19) is monitored as each teat cup (9' - 9'''') is sequentially attached to its resp. teat (13' - 13'''') and a teat cup (9' - 9'''') is determined to be incorrectly attached if the measured pressure is different from the desired pressure in the working fluid supply line (19).

Description: Sensor for milking machines Technical field of the invention The present invention relates to a sensing means and method for sensing for a milking machine of the type mentioned in the preambles of claims 1, 5 and 6. Background of the invention When automatically connecting teat cups to the teats of an animal which is to be milked by a milking machine it is possible that the teat cup is incorrectly attached. In automatic milking systems the teat cups are positioned under the teats and lifted one at a time to a position surrounding the respective teats. The teat cups are retained on the teats by a vacuum present in the teat cup. It is possible that a teat cup falls off a teat or is not even correctly positioned on the teat and this can be sensed by measuring the vacuum in each teat cup by means of a vacuum sensor provided in each teat cup or in the suction line to each teat cup. A disadvantage with this system is that it requires an expensive vacuum sensor for each teat cup. Objects of the invention An object of the present invention is to provide sensor means and sensing methods which do not suffer from the disadvantages of the prior art system. The object is achieved by means of sensor systems and methods having the features stated in the characterising parts of claim 1 and claims 5 and 6 respectively. Further embodiments of the invention have the features mentioned in the dependent claims. Summary of the invention The present invention relates to a teat cup attachment monitoring device for use in a milking machine in which teat cups are attached in sequence to teats and in which the attachment sequence is determined by control means. The teats cups are supplied with a working fluid from a common source which comprises means for measuring the pressure of the working fluid and comparison means for comparing the pressure of the working fluid and/or the rate of change of the pressure of the working fluid against a desired value of the pressure of the working fluid and/or the rate of change of the pressure of the working fluid. In this way it is possible to determine whether the device is working according to a desired model of how it should be working. According to the present invention, a teat cup attachment monitoring device is presented. The control means determines a time window for the attachment of each resp. teat cup and said comparison means compares the measured pressure of the working fluid and/or the rate of change of the pressure of the working fluid against a desired value of the pressure of the working fluid and/or the rate of change of the pressure of the working fluid during said time windows. In this way it can be detected if a teat cup has not been correctly attached and the resp. teat cup can be identified. In accordance with an embodiment of the present invention a teat cup attachment monitoring device is presented in which the working fluid is an underpressure connected to a teat space in each teat cup. It is therefore possible to use this device with already existing teat cups which use an underpressure in the teat space. In accordance with another embodiment of the present invention a teat cup attachment monitoring device is presented in which the working fluid is compressed air or liquid connected to a pulsation chamber in each teat cup. It is therefore possible to use this device with already existing teat cups which use compressed air or liquid in the pulsation chamber. In accordance with a further embodiment of the present invention a teat cup attachment monitoring device is presented in which means for measuring the pressure of the working fluid comprising a single pressure sensor provided on a common working fluid line connected between said teat cups and a working fluid source. In this way the device can be constructed economically as one pressure sensor can be used to monitor several teat cups. In accordance with the present invention a method for monitoring the attachment of teat cups in a milking machine is presented which comprises the steps of: providing a single pressure sensor in a common working fluid line connected between teat cups and a working fluid source; providing a series of sequential time windows (tw \ -tw_ι) during which a respective teat cup is to be attached to a teat; monitoring the pressure in the common working fluid line during each time window; comparing the monitored pressure for each time window against a desired pressure for each time window; determining that said resp. teat cup is incorrectly attached if the monitored pressure during the resp. time window is different to the desired pressure for the resp. time window. Using this method leads to that the device can be constructed economically as one pressure sensor can be used to monitor several teat cups. In accordance with an embodiment of the present invention a method for monitoring the attachment of teat cups in a milking machine is presented which has the steps of: providing a single pressure sensor in a common working fluid line connected between teat cups and a working fluid source; providing a series of sequential time windows during which a respective teat cup is to be attached to a teat; attaching said resp. teat cup to a teat during said resp. time window; monitoring the rate of change of pressure in the common working fluid line during each time window; comparing the monitored rate of change of pressure for each time window against a desired rate of change of pressure for each time window; determining that said resp. teat cup is incorrectly attached if the monitored rate of change of pressure during the resp. time window is different to the desired rate of change of pressure for the resp. time window. Using this method leads to that the device can be constructed economically as one pressure sensor can be used to monitor several teat cups. In accordance with an embodiment of the present invention a method for monitoring the attachment of teat cups in a milking machine is presented which has the steps of: that if teat cup is determined to be incorrectly attached it is removed and the attaching, monitoring, comparing and determining steps are repeated. This method provides a way of automatically refitting an incorrectly attached teat cup without requiring any operator intervention. In the sensor system and method of sensing according to the invention a single vacuum sensor is provided in a suction line common to all the teat cups. The milking machine has a control device, such as a computer, which controls a teat cup attaching means such as a robot arm. This arm is commanded by the computer to offers one teat cup at time to its intended teat on the animal. As each teat cup is correctly attached the air flow through each respective teat cup is stopped and the pressure in the suction line is reduced. The pressure in the suction line is sensed by the vacuum sensor and the sensed value monitored by the control device during the attachment operation. If no change in pressure, or an in-sufficient change in pressure, is detected during the time interval or time window allowed for the attachment of a particular teat cup then the control device concludes that the teat cup is incorrectly attached and orders the robot arm to attempt to reattach the teat cup. In a further embodiment of the invention the rate of change of the sensed pressure in a pressure line connected to a pulsation chamber in a teat cup is measured. In this case during the teat cup attachment phase of a milking operation a pulsating pressure is applied to the pulsation chambers of all the teat cups as they are being attached. If a teat cup contains a teat then the rate of the rise in pressure in the pulsation chamber will be greater than if there is no teat in the teat cup. This is because in the first instance the inward expansion of the pulsation chamber wall will be resisted by the teat after only a short period of time. The resistance exerted by the teat causes the pressure to rise. In the second instance there is only a low resistance to the inward expansion caused by the inherent elasticity of the chamber wall until the chamber wall completely fills the centre of the teat cup at which point the pressure rises quickly. The maximum pressure possible in both instances is the same. By monitoring the rate of pressure rise during the teat attachment window for each teat cup it is possible to determine if the teat cup has been correctly attached. Drawing summary The invention will be described in more detail below with reference to the accompanying figures in which: Fig. 1 shows schematically a first embodiment of a milking machine in accordance with the present invention; Fig. 2a) - 2c) show examples of a graphs showing pressure against time sensed by a sensor while teat cups are attached in a correct way or while incorrect attachment of teat cups occur, all of the figures according to the first embodiment of the present invention; Fig. 3 shows schematically a second embodiment of a milking machine in accordance with the present invention; Fig. 4 shows an example of a graph showing the pressure against time sensed by a sensor according to the first embodiment of the present invention. Detailed description of the embodiments Figure 1 shows a schematic arrangement of a milking machine 1 for automatic milking of a dairy animal such as a cow, goat, buffalo or the like. A robot arm 3 controlled by control means, for example computer 5, moves a milking head 7 comprising four teat cups 9 "-9"" under the udder 11 of the animal. The teat cups are attached to the teats 13 '-13 "" one after the other by the robot arm 3. The attachment sequence is determined and controlled by control means, preferably computer 5 which provides a time window twι-tw4 for attaching each teat cup 9'- 9"". Each teat cup 9'-9"" has a respective teat space 15'-15"" and pulsation chamber 35 '-35'"' each connected to a working fluid supply. In this example the working fluid is underpressure air for the teat cups and compressed air for the pulsation chambers. For the sake of ease of illustration only schematic attachments points for the compressed air supply lines for the pulsation chambers are shown in this figure, the air supply lines being omitted. Each teat cup 9'-9"" is connected by a respective teat cup underpressure line, commonly called a vacuum line, 17'-17"" to common vacuum line 19 which is connected to suction supply means such as a so-called vacuum tank 21 and vacuum pump 23. A pressure sensor 25 is connected to, and senses the pressure in, common vacuum line 19. The sensed pressure is transmitted to computer 5. When no teat cups 9'-9"" are attached to any teats the pressure sensed by pressure sensor 25 is relatively high as common vacuum line 19 is essentially open to ambient air which is sucked into all four teat cups 9 '-9'"'. As each teat cup 9'-9 " " is attached to a respective teat 13 '- 13 " " a distinct drop in pressure occurs in common vacuum line 19 during the respective time window twi - tw4 as each teat cup 9'-9"" is blocked in turn by a resp. teat 13'-13"". The pressure in the common vacuum line 19 reaches a minimum value when all four teat cups 9'-9"" are attached to teats 13'-13"". The computer 5 monitors the pressure sensed by pressure sensor 25 during each time window. If a distinct drop in pressure is detected and maintained during a time window twi-tw4 then computer 5 can decide that the respective teat cup 9 '-9'"' being attached during the time window twi -tw4 was correctly attached. If no, or an insignificant, change in pressure is detected then computer 5 can decide that the respective teat cup 9 '-9'"' is not correctly attached and it can command the robot arm 3 to attempt to attach the resp. teat cup 9'-9"" again. Figure 2a) shows a graph of pressure sensed in the common vacuum line against time while a correct attachment of four teat cups 9 '-9'"' is performed. Figure 2b) shows a similar graph in which the third teat cup 9 ' " is incorrectly attached on the first attempt in time window 1W3 but this teat cup is subsequently correctly attached in time window tw3 ' . In an improved embodiment of the invention the rate of change of pressure in common vacuum line 19 is monitored. As a teat cup 9 '-9'"' is attached to a teat the reduction in pressure occurs gradually as more of each teat 13 '-13'" is introduced into the respective teat cup 9'-9"". If any of the teat cups 9 '-9'"' is incorrectly placed with its open end against the udder of the animal or a surrounding surface then it may become attached to the udder or surface because of the suction caused by the vacuum in the teat cup. This attachment will occur suddenly and cause an unusually rapid drop in the pressure in common vacuum line 19. If this is detected the computer 5 can command robot arm 3 to reattempt to attach the respective teat cup 9'-9"". This is shown in time interval tW2 in figure 2c) in which the teat cup is firstly incorrectly attached, released and then correctly attached in time interval In a further embodiment of the invention shown in Figure 3 a milking device has control means 26 for controlling robot arm 27. A working fluid such as compressed air is supplied from a pump 28 to a compressed air reservoir 29. A common pressure line 30 connects the reservoir 29 via a valve 31 to individual compressed air supply lines 32 '-32'"' each leading to a resp. pulsation chamber 35 '-35'"' in a resp. teat cup 9' -9"". The rate of change of the sensed pressure in the common pressure line 30 is measured by a pressure sensor 34. For the sake of ease of illustration only schematic attachments points for the vacuum supply lines for the teat chambers are shown in this figure, the vacuum supply lines being omitted. In this embodiment during the teat cup attachment phase of a milking operation valve 31 is operated so that a pulsating pressure is applied to the pulsation chambers 35 '-35'"' of all the teat cups 9 '-9'"' as they are being attached. This pulsating pressure causes the flexible pulsation chamber walls 36 '-36 " " to expand and contract. If a teat cup 9 '-9'"' contains a teat then the rate of the rise in pressure measured by pressure sensor 34 will be greater than if there is no teat in the teat cup 9'-9"". This is because the expanding pulsation chamber wall 36'-36"" will soon come into contact with the enclosed teat 37 '-37'"' and therefore the inward expansion of the pulsation chamber wall 36'-36"" will be resisted by the teat 37'- 37"" after only a short period of time. The resistance to expansion caused by the teat causes the pressure to rise steeply as a teat is less compressible than air. This is shown by the curve in figure 4 which shows the variation of pressure against time as the four teat cups 9 '-9'"' are attached one after the other. In the time window tai the first teat cup is attached. The rate of pressure rise dpl/dtl has a distinctive shape which can be detected by control means 26. In the time window ta2 the second teat cup is attached. The rate of pressure rise dp2/dt2 has a steeper distinctive slope which can be detected by control means 26 and so on for time windows ta3, ta4. In the case that there are no teats 37'-37"" in any of the teat cups 9'-9"" then there is only a low resistance to the inward expansion caused by the inherent elasticity of the pulsation chamber walls 36'-36"" until the pulsation chamber walls 36'-36"" completely fill the teat cups 9'-9"" at which point the pressure rises quickly. This shown by the curve for time window tao in figure 4 where an example of a possible pressure rise without a teat in the teat cup is shown by a solid line and an example of a possible pressure rise with a teat in the teat cup is shown by a dashed line. Similarly the rate of fall in pressure depends on the presence or absence of teats in the pulsation chambers. By monitoring the actual rate of pressure rise during the teat attachment window resp. taι-ta4 for each resp. teat cup 9 '-9'"' and comparing the actual rate against a known or calculated desired rate it is possible to determine if the teat cup 9 '-9'"' has been correctly attached. While this embodiment has been illustrated as using a compressed air source to provide compressed air as the working fluid it will be understood by the skilled person that the working fluid could be air at an underpressure from a vacuum source, the desired pulsating pressure being produced by allowing air at atmospheric pressure to enter the pulsation chambers while a vacuum is connected to the teat space. It is also possible in a further embodiment to measure the time it takes for the pressure to rise from its low value to its peak value to determine if a teat is correctly attached as, as shown in figure 4, the time taken to reach the peak pressure is inversely proportional to the number of attached teats. Thus the time to reach the peak pressure can be compared against predetermined times. These predetermined time are dependent on how many teat cups are attached. While the invention has been illustrated by the use of air as the working fluid it is of course conceivable to use an hydraulic system instead.

Claims: Claims 1. Teat cup attachment monitoring device for use in a milking machine in which teat cups (9 '-9'"') are attached in sequence to teats and in which the attachment sequence is determined by control means (5, 26) wherein the teats cups (9'-9"") are supplied with a working fluid from a common source comprising means for measuring the pressure of the working fluid and comparison means for comparing the pressure of the working fluid and/or the rate of change of the pressure of the working fluid against a desired value of the pressure of the working fluid and/or the rate of change of the pressure of the working fluid, characterised in that said control means determines a time window (tw i -tW4; taι-t 4) for the attachment of each resp. teat cup (9'-9"") and said comparison means compares the measured pressure of the working fluid and/or the rate of change of the pressure of the working fluid against a desired value of the pressure of the working fluid and/or the rate o f change of the pressure of the working fluid during said time windows (twι-tw4; tai -ta4). 2. Teat cup attachment monitoring device according to claim 1, characterised in that said working fluid is an underpressure connected to a teat space (15'- 15"") in each teat cup (9'-9""). 3. Teat cup a t tachment monitoring device according to claim 1 or 2, characterised in that said working fluid is compressed air or liquid connected to a pulsation chamber (35'-35"") in each teat cup (9'-9""). 4. Teat cup attachment monitoring device according to any of the previous claims, characterised in that said means for measuring the pressure of the working fluid (25; 34) comprises a single pressure sensor (25, 34) provided on a common working fluid line (19; 30) connected between said teat cups (9'-9"") and a working fluid source (21, 23; 28, 29). 5. Method for monitoring the attachment of teat cups in a milking machine, characterised by the steps of: providing a single pressure sensor in a common working fluid line (19; 30) connected between teat cups (9'-9"") and a working fluid source (21, 23; 28, 29); providing a series of sequential time windows (twι-tW4) during which a respective teat cup (9 '-9'"') is to be attached to a teat; monitoring the pressure in the common working fluid line (19; 30) during each time window (twι-tW4); comparing the monitored pressure for each time window (twi -1W4) against a desired pressure for each time window (twι-tW4); and determining that said resp. teat cup (9 '-9'"') is incorrectly attached if the monitored pressure during the resp. time window is different to the desired pressure for the resp. time window. 6. Method for monitoring the attachment of teat cups in a milking machine, characterised by the steps of: providing a single pressure sensor in a common working fluid line (19; 30) connected between teat cups (9 '-9"") and a working fluid source (21, 23; 28, 29); providing a series of sequential time windows (1W1-1W4: taι-ta4) during which a respective teat cup (9'-9"") is to be attached to a teat; attaching said resp. teat cup (9'-9"") to a teat during said resp. time window (twι -tW4: ta]-ta4); monitoring the rate of change of pressure in the common working fluid line (19; 30) during each time window (twι-tW4); comparing the monitored rate of change of pressure for each time window (taι-ta4) against a desired rate of change of pressure for each time window (taι-ta4); and determining that said resp. teat cup (9 '-9'"') is incorrectly attached if the monitored rate of change of pressure during the resp. time window (tai -ta4) is different to the desired rate of change of pressure for the resp. time window (tai - ta_χ). 7. Method according to any of claims 5 and 6, characterised by the step: that if said resp. teat cup (9'-9"") is determined to be incorrectly attached it is removed and the resp. attaching, monitoring, comparing and determining steps are repeated. 8. Automated milking system, characterised in that said automated milking system comprises a monitoring device according to any of claims 1-4. 9. Automated milking system, characterised in that said automated milking system comprises means for carrying out a method according to any of claims 5-7.

Inventors: ANDERSSON LARS, LUNDWALL JONAS, ANDERSSON, LARS, LUNDWALL, JONAS
Applicants: ALFA LAVAL AGRI AB, ANDERSSON LARS, LUNDWALL JONAS, ANDERSSON, LARS, LUNDWALL, JONAS
Application year: 1999
Main classification: A01J5
IPC codes: A01J5