Patent Application
20240032499
The present invention relates generally to milk-flow and cooling regulation. Especially, the invention relates to a control unit arranged to control a flow of milk through a cooling system between a balance tank and a storage tank and a corresponding computer-implemented method. The invention also relates to a computer program and a non-volatile data carrier storing such a computer program.
For quality and hygienic reasons it is important that the temperature of the milk that is extracted from milk-producing animals is kept sufficiently low throughout the storage process. The rate at which an incoming milk flow enters the system is typically unstable, at least to some extent, due to the fact that different animals produce different amounts of milk per unit time. The number of animals from which milk is extracted may also vary during a milking sequence. It is therefore challenging to control the cooling of the milk between an input balance tank and a storage tank, where the milk is held until being transported to a dairy, or similar facility.
WO 97/16962 shows an apparatus for cooling a product, which apparatus comprises a heat exchanger structure including a first evaporator and a second evaporator separate from the first evaporator, wherein a first heat exchanger incorporates the first evaporator and a second heat exchanger incorporates the second evaporator. In operation, the product or an intermediate heat transfer medium is cooled in at least two first stages. During the first stage, heat is withdrawn from the product or the medium by the first evaporator cooling the product or the medium to an intermediate temperature. During the second stage, heat is withdrawn from the product or the medium by the second evaporator further cooling the product or the medium to the desired temperature. Since the product or the medium is partially cooled by an evaporator operating at a higher evaporating temperature than required for achieving the desired temperature, an improved energy efficiency is achieved. WO 97/16962 further discloses a control unit for controlling the temperature of the milk by controlling a pump, so that the flow rate through the heat exchanger structure is increased if a temperature of the milk downstream of the heat exchanger is too low and vice versa the flow rate is decreased if the temperature is too high.
Thus, there is an apparatus enabling adaptive pumping and cooling of a product, such as extracted milk, which apparatus may be applied to cool the product while transporting it from the balance tank to the storage tank. However, the known solution leaves room for further economizing of the energy resources used for pumping and cooling the extracted milk.
The object of the present invention is therefore to offer a solution that solves the above problem and enables more efficient pumping and cooling of extracted milk before storing the milk in a storage tank.
According to one aspect of the invention, the object is achieved by a control unit arranged to control a flow of milk through a cooling system between a balance tank and a storage tank. The balance tank is here presumed to receive an input in the form of milk extracted from a number of milking animals. The control unit is configured to generate a first control signal to a milk pump in the cooling system, which milk pump is arranged to cause the flow of milk to be pumped out from the balance tank. The balance tank contains at least one sensor configured to produce a level-indicating signal reflecting a milk level in the balance tank in relation to low- and high-threshold levels respectively. The control unit is configured to receive the level-indicating signal and a temperature-indicating signal from a temperature sensor measuring a temperature of the flow of milk before entering the storage tank. The control unit is configured to generate the first control signal based on the level-indicating signal and the temperature-indicating signal so that a speed of the milk pump is controlled by the first control signal being based on the temperature-indicating signal exclusively if the level-indicating signal reflects that the milk level in the balance tank is between the low-threshold level and the high-threshold level.
In this way, when the milk level is within said range, the milk flow (pump speed) is efficiently controlled by the temperature sensor to achieve a desired/stable temperature on the milk flowing from the cooling system and into the storage tank. The control unit is hereby made independent on milk flow sensors or meters, which are generally more complicated/expensive and unhygienic in relation to temperature sensors. Furthermore, the milk level sensor could be configured as two floats located at the low- and high-threshold levels in the balance tank, but it could alternatively be any other type of milk-level sensor (such as a hydrostatic pressure sensor) capable of also producing a continuous/linear level-indicating signal of the different milk levels between the low- and high-threshold levels. The above control unit is advantageous in that it enables a different type of control of the milk pump (as well as the cooling system) at more extreme milk levels in the balance tank. Hence, the above control unit is advantageous because it can for instance avoid unnecessary operation of the milk pump (and cooling system) when the milk level is below the low-threshold level, whereas the milk pump may run at a predetermined high (maximum) speed when the milk level is above the high-threshold level. In other words, the milk temperature is no longer controlling the pump speed when the milk level is below and above the low- and high-threshold levels respectively, so that more important (overriding) parameters such as energy saving and safeguarding a receiving capacity of the balance tank is enabled by the control unit. It should hereby be emphasized that the milk temperature can nevertheless be kept within an acceptable desired range in a high (maximum) pump speed operation at a high-threshold level by temporarily increasing the cooling effect on the cooling system.
According to one embodiment of this aspect of the invention, the control unit is configured to generate the first control signal such that the milk pump causes the flow of milk to be pumped out from the balance tank at a predetermined high speed if the level-indicating signal reflects that the milk level in the balance tank is above or equal to the high-threshold level. This is desirable because it minimizes the risk that the balance tank is flooded, which, in turn, is deemed to be more critical than the milk temporarily attaining an excessive temperature due to insufficient cooling in the cooling system. Preferably, therefore, the predetermined high speed represents a highest possible pump speed for the milk pump.
According to another embodiment of this aspect of the invention, the control unit is configured to generate a second control signal based on the temperature-indicating signal such that a cooling capacity of the cooling system is increased if the temperature indicating signal reflects a milk temperature above a set temperature. Thus, the milk pump will be operated at a predetermined high speed also when the milk temperature is high, and the temperature-indicating signal may be used to increase a capacity of a chiller and/or a coolant pump speed.
Analogously, according to another embodiment of this aspect of the invention, the control unit is configured to generate the second control signal based on the temperature-indicating signal such that the cooling capacity of the cooling system is decreased if the temperature-indicating signal reflects a milk temperature below the set temperature. Thus, the milk pump will be operated at the predetermined high speed when the milk temperature is low, and the temperature-indicating signal is used to decrease a cooling capacity of the cooling system by decreasing the cooling capacity of the chiller and/or the speed of the coolant pump to further economize the energy usage.
According to still another embodiment of this aspect of the invention, the control unit is configured to generate the first control signal such that the milk pump causes the flow of milk to be pumped out from the balance tank at a predetermined low speed if the level-indicating signal reflects that the milk level in the balance tank is below or equal to the low-threshold level. This saves energy and reduces the risk of emptying the balance tank. Preferably, the predetermined low speed represents that the milk pump is inactive. Furthermore, the coolant system including a chiller and a coolant pump is preferably placed in an idle mode or turned off, whenever the milk pump is inactive. In this way the embodiment saves further energy.
According to yet another embodiment of this aspect of the invention, the control unit is configured to generate the first control signal based on the temperature-indicating signal so that the milk flow is caused to be pumped out from the balance tank at a predetermined nominal speed if the temperature-indicating signal indicates a milk temperature within a predefined interval from a set temperature. If, however, the temperature-indicating signal indicates a milk temperature below said predefined interval, the control unit is configured to generate the first control signal so that the milk flow is caused to be pumped out from the balance tank at an elevated speed above the predetermined nominal speed; and if the temperature-indicating signal indicates a milk temperature above said predefined interval, the control unit is configured to generate the first control signal so that the milk flow is caused to be pumped out from the balance tank at a lowered speed below the predetermined nominal speed. Namely, this allows a high milk throughput while keeping the milk temperature within an acceptable range and economizing the energy usage.
According to still another embodiment of this aspect of the invention, the cooling system contains a heat exchanger configured to transfer heat energy from the flow of milk to a cooling medium being circulated in a chiller by means of a coolant pump operating in response to a second control signal. Here, the control unit is configured generate the second control signal based on the temperature-indicating signal so that a flow of the cooling medium and/or the cooling capacity of the chiller increases if the temperature-indicating signal indicates a milk temperature above said predefined interval during a first uninterrupted period.
Analogously, the control unit is configured generate the second control signal based on the temperature-indicating signal so that the flow of the cooling medium and/or the cooling capacity of the chiller decreases if the temperature-indicating signal indicates a milk temperature below said predefined interval during a second uninterrupted period. Thereby, the chiller may also attain an efficient energy usage.
According to another aspect of the invention, the object is achieved by a computer-implemented method for controlling a flow of milk through a cooling system between a balance tank and a storage tank, where the balance tank receives an input in the form of milk extracted from a number of milking animals, and the method involves receiving a temperature-indicating signal from a temperature sensor measuring a temperature of the flow of milk before entering to the storage tank. The method also involves generating a first control signal to a milk pump in the cooling system, which milk pump is arranged to cause the flow of milk to be pumped out from the balance tank, and which first control signal is generated based on the temperature-indicating signal. It is presumed that the balance tank contains at least one sensor configured to produce a level-indicating signal reflecting a milk level in the balance tank in relation to low- and high-threshold levels respectively. Additionally, the method further involves receiving the level-indicating signal, and generating the first control signal on the further basis of the level-indicating signal. Here, a speed of the milk pump is controlled by the first control signal being based on the temperature-indicating signal exclusively if the level-indicating signal reflects that the milk level in the balance tank is between the low-threshold level and the high-threshold level. The advantages of this method, as well as the preferred embodiments thereof, are apparent from the discussion above with reference to the proposed control unit.
According to a further aspect of the invention, the object is achieved by a computer program loadable into a non-volatile data carrier communicatively connected to a processing unit. The computer program includes software for executing the above method when the program is run on the processing unit.
According to another aspect of the invention, the object is achieved by a non-volatile data carrier containing the above computer program.
Further advantages, beneficial features and applications of the present invention will be apparent from the following description and the dependent claims.
The invention is now to be explained more closely by means of preferred embodiments, which are disclosed as examples, and with reference to the attached drawings.
In
The control unit 110 is arranged to control a flow of milk F through a cooling system 170 between a balance tank 120 and a storage tank 130. The storage tank 130 is adapted to accumulate milk that has been collected during a relatively long period, namely between consecutive pickups of the milk for further transport to a dairy or similar facility, which pickups typically occur every 24 or 48 hours. Consequently, the storage tank 130 has a comparatively large capacity. The balance tank 120, on the other hand, has a comparatively low capacity because here the milk is just buffered briefly before being forwarded through the cooling system 170. The balance tank 120 is adapted to receive an input MIN in the form of milk having been extracted from a number of milking animals. Thus, one or more milking points may feed milk to the balance tank 120 directly or for example via a so-called end unit, or receiver.
A temperature sensor 140 is arranged on a milk conduit feeding the milk into the storage tank 130. The temperature sensor 140 is configured to measure a temperature of the flow of milk F before entering the storage tank 130. The balance tank 120 contains at least one sensor, here represented by a first sensor 121 and a second sensor 122, which are configured to produce a level-indicating signal s(LTH:HTH) reflecting a milk level L in the balance tank 120 in relation to a low-threshold level LTH and a high-threshold level HTH respectively. For example, the low-threshold level LTH may represent 10% of a storage capacity of the balance tank 120 and the high-threshold level HTH may represent 90% of the storage capacity of the balance tank 120.
The control unit 110 is configured to receive the temperature-indicating signal T from the temperature sensor 140. The control unit 110 is also configured to receive the level-indicating signal s(LTH:HTH) from the at least one sensor 121/122. Based on the temperature-indicating signal T and the level-indicating signal s(LTH:HTH), the control unit 110 is configured to generate a first control signal C1 to a milk pump 150 in the cooling system 170, which milk pump 150 is arranged to cause the flow of milk F to be pumped out from the balance tank 120 and through the cooling system 170. Specifically, the first control signal C1 is generated based on the temperature-indicating signal T and the level-indicating signal s(LTH:HTH) in such a manner that a speed of the milk pump 150 is controlled by the first control signal C1 based on the temperature-indicating signal T exclusively if the level-indicating signal s(LTH:HTH) reflects that the milk level L in the balance tank 120 is between the low-threshold level LTH and the high-threshold level HTH. Otherwise, i.e. when the milk level L does not lie within the range given by the low- and high-threshold levels LTH and HTH, the first control signal C1 is not based on the temperature-indicating signal T as will be explained below, inter alia with reference to
According to one embodiment of the invention, the control unit 110 is configured to generate the first control signal C1 such that the milk pump 150 causes the flow of milk F to be pumped out from the balance tank 120 at a predetermined high speed FHI, say at 80% or more of the milk pump's 150 maximum speed, if the level-indicating signal s(LTH:HTH) reflects that the milk level L in the balance tank 120 is above or equal to the high-threshold level HTH. Namely, if the milk level L is above or equal to the high-threshold level HTH, there is an imminent risk that the balance tank 120 will be flooded. In such a situation it is important that the milk level L is reduced quickly. Therefore, the predetermined high speed FHI preferably represents a highest possible pump speed for the milk pump 150 thus accomplishing a quickest possible reduction of the milk level L in the balance tank 120.
Additionally, it may be preferable if the control unit 110 is configured to generate the first control signal C1 such that the milk pump 150 causes the flow of milk F to be pumped out from the balance tank 120 at a predetermined low speed Fro, say at 20% or less of the milk pump's 150 maximum speed, if the level-indicating signal s(LTH:HTH) reflects that the milk level L in the balance tank 120 is below or equal to the low-threshold level LTH. Namely, otherwise, in such a case, the balance tank 120 might be emptied and undesired air bubbles risk being injected into the milk. It is therefore advantageous that the predetermined low speed Fro represents that the milk pump 150 is inactive, i.e. does not cause any flow of milk at all to be pumped out from the balance tank 120.
According to one embodiment of the invention, the control unit 110 is configured to generate a second control signal C2 based on the temperature-indicating signal T such that a cooling capacity of the cooling system 170 is increased if the temperature-indicating signal T reflects a milk temperature above a set temperature TSET of say 3.5 degrees Celsius. This means that the milk pump 150 may be operated at a relatively high, preferably fixed speed, which, in turn, renders it possible to increase a cooling capacity of a chiller 167 and/or a speed of a coolant pump 165 in the cooling system 170 based on the temperature-indicating signal T.
Analogously, according to another one embodiment of the invention, the control unit 110 is preferably configured to generate the second control signal C2 based on the temperature-indicating signal T such that the cooling capacity of the cooling system 170 is decreased if the temperature-indicating signal T reflects a milk temperature below the set temperature TSET. Namely, in such a case, energy can be economized by reducing the cooling of the milk.
According to one embodiment of the invention, the control unit 110 is configured to generate the first control signal C1 based on the temperature-indicating signal T so that the milk flow F is caused to be pumped out from the balance tank 120 at a predetermined nominal speed FNOM, say around 50% of the milk pump's 150 maximum speed, if the temperature-indicating signal T indicates a milk temperature within a predefined interval TR from a set temperature TSET, say between 3 and 5 degrees Celsius. Thus, a steady milk flow F can be fed efficiently through the cooling system 170 into the storage tank 130.
If the temperature-indicating signal T indicates a milk temperature below the predefined interval TR, the control unit 110 is configured to generate the first control signal C1 based on the temperature-indicating signal T so that the milk flow F is caused to be pumped out from the balance tank 120 at an elevated speed FELVD, i.e. at % or more of the milk pump's 150 maximum speed, above the predetermined nominal speed FNOM, thus causing the milk to be less cooled while forwarding more milk per unit time into the storage tank 130. It is additionally possible to hereby use the further second control signal C2 to also decrease the speed of the coolant pump 165. In this way, less heat will be taken from the milk.
If the temperature-indicating signal T indicates a milk temperature above said predefined interval TR, the control unit 110 is instead configured to generate the first control signal C1 based on the temperature-indicating signal T so that the milk flow F is caused to be pumped out from the balance tank 120 at a lowered speed FLWD below the predetermined nominal speed FNOM, i.e. at 50% or less of the milk pump's 150 maximum speed, thus cooling the milk more while passing through the cooling system 170 before entering the storage tank 130. It is also possible to hereby use the further second control signal C2 to increase the speed of the coolant pump 165. In this way, more heat will be taken from the milk.
According to one embodiment of the invention, the cooling system 170 contains a heat exchanger 160, for example a plate heat exchanger (PHE), which is configured to transfer heat energy from the flow of milk F to a cooling medium C, e.g. containing glycol being circulated in the chiller 167 by means of the coolant pump 165. The coolant pump 165 is adapted to operate in response to a second control signal C2.
Here, the control unit 110 is further configured to generate the second control signal C2 based on the temperature-indicating signal T so that a flow of the cooling medium C and/or the cooling capacity of the chiller 167 increases, if the temperature-indicating signal T indicates a milk temperature above the predefined interval TR during a first uninterrupted period, say 60 seconds. Thereby, any excessive milk temperatures may be reduced efficiently.
Further, if the temperature-indicating signal T indicates a milk temperature below the predefined interval TR during a second uninterrupted period, say 60 seconds, the control unit 110 is configured generate the second control signal C2 based on the temperature-indicating signal T so that the flow of the cooling medium C and/or the cooling capacity of the chiller 167 decreases. Hence, unnecessary cooling of the milk is avoided and energy is conserved.
In order to sum up, and with reference to the flow diagram in
In a first step 410, a temperature-indicating signal T is received from a temperature sensor 140 measuring a temperature of the flow of milk F before entering the storage tank 130. A level-indicating signal s(LTH:HTH) is also received in step 410, which level-indicating signal s(LTH:HTH) reflects a milk level in the balance tank 120 in relation to low- and high-threshold levels respectively.
A subsequent step 420 checks if the level-indicating signal s(LTH:HTH) reflects that the milk level in the balance tank 120 is within the low- and high-threshold levels; and if so, a step 430 follows. Otherwise, the procedure continues to a step 440.
In step 430, the milk flow is controlled to a nominal rate by generating the first control signal C1 to the milk pump 150 in the cooling system 170. Thereafter, the procedure loops back to step 410.
In step 440, it is checked if the level-indicating signal s(LTH:HTH) reflects that the milk level in the balance tank 120 is above the high-threshold level; and if so, a step 450 follows. Otherwise, the procedure continues to a step 460.
In step 450, the milk flow is controlled to a high rate via the first control signal C1 to the milk pump 150. Thereafter, the procedure loops back to step 410.
In step 460, the milk flow is instead controlled to a low rate via the first control signal C1 to the milk pump 150. Thereafter, the procedure loops back to step 410.
All of the process steps, as well as any sub-sequence of steps, described with reference to
Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.
The term “comprises/comprising” when used in this specification is taken to specify the presence of stated features, integers, steps or components. The term does not preclude the presence or addition of one or more additional elements, features, integers, steps or components or groups thereof. The indefinite article “a” or “an” does not exclude a plurality. In the claims, the word “or” is not to be interpreted as an exclusive or (sometimes referred to as “XOR”). On the contrary, expressions such as “A or B” covers all the cases “A and not B”, “B and not A” and “A and B”, unless otherwise indicated. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.
It is also to be noted that features from the various embodiments described herein may freely be combined, unless it is explicitly stated that such a combination would be unsuitable.
The invention is not restricted to the described embodiments in the figures, but may be varied freely within the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2051519-3 | Dec 2020 | SE | national |
This application is the U.S. national phase of International Application No. PCT/SE2021/051271 filed Dec. 16, 2021 which designated the U.S. and claims priority to SE Patent Application No. 2051519-3 filed Dec. 21, 2020, the entire contents of each of which are hereby incorporated by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/SE2021/051271 | 12/16/2021 | WO |
