PROCEDURE AND MEANS IN VOLUME MEASUREMENTS OF MILK

Abstract: The means (10) in milk gathering from milk producers taking place with the aid of tank cars comprises a flexible suction tube (13) or a suction pipe (11) and a flexible suction tube (13), an air separator (14) provided with a venting means (15), a pump means (18) and a volume meter (20). The means (10) is employed to draw the milk from a farm tank or from a milk can to the air separator (14), whence the milk is further conducted to the volume meter (20). With a view to avoiding technical problem solutions having a detrimental effect on the accuracy of measurement, the pump means (18) has been so disposed with reference to the air separator (14) that the air separator (14) is located on the intake side of the pump means (18). The pump means (18) has been provided with a control system (23) adapted to control the pump means (18) in such manner that when the milk surface reaches in the air separator (14) a first upper level (B) the pump means (18) is switched to operate at a slow pumping rate. When the milk surface in the air separator (14) reaches a second upper level (C) higher than the said first upper level (B) the pump means (18) is switched to operate at a higher pumping rate. The operation of the venting means (15) is so controlled with a control means (22) that the venting means (15) is switched to operate when the pressure in the air separator (14) is higher than a predetermined limit pressure (Pr), which is lower than atmospheric pressure. The control system (23) stops the pump means (18) when the milk surface in the air separator (14) falls to a lowest level (A).

Description: Procedure and means in volume measurements of milk ~t The present invention concerns a procedure in connection with milk gathering from milk producers by the aid of tank cars, for volume measurement of the milk, according to which procedure the milk is conducted through a flexible suction tube or through a suction pipe 5 and a flexible suction tube into an air separator and from the air separator to a volume meter. In addition, the invention concerns a means in connection with milk gathering from the milk producers by the aid of milk tank cars, for 10 volume measurement of the milk, said means comprising a flexible suction tube, or a flexible suction tube and a suction pipe, an air separator provided with a venting means, a pump means and a volume meter, and with said means milk being drawn from a farm tank or milk can into the air separator, wherefrom the milk is further conducted 15 to the volume meter- Volume measurements of liquids are carried out e.g. in connection with milk gathering from milk producers by the aid of milk tank cars. The milk is pumped through a pipe system into an air separator 20 container, wherein the liquid surface will rise until a closing member affixed to the shaft of a float sensing the liquid surface in the end closes the air hole leading to a venting valve. The upper part of the air separator container thus constitutes a closed system in which a pressure builds up gradually, which after rising to a 25 given value overcomes the spring force of a directional valve dis- "" * posed after the meter, and the directional valve will open. Thereby, * ~ milk starts to flow through the meter and keeps on flowing until the pump pushes nothing but air into the air separator container. The surface of the liquid in the air separator container starts 30 then to go down, and in the end the float is far enough down to cause the air hole to open and the pressure to discharge through the venting valve. The venting valve then closes, and the volume * measuring of milk is ended. A volume measuring system for liquids of k. OM this kind has been disclosed e.g. in the Finnish patent application No. 780025, which is referred to as regards the state of art. In the volume measurement system as described in the foregoing are presented several technical solutions, which exert an unfavourable effect on the accuracy of measurement. First, the pump has been mounted before the air separator, which results in mixing of air and milk to form bubbles of microscopic size. For this reason, the complete separation of air from the milk is extremely difficult and often outright impossible, as a consequence of which an error of measurement is incurred in .the volume measuring of milk. Secondly, in some apparatus applications, there is after the pump a vertical pipe run, wherein the residual milk quantity after measuring varies from measurement to measurement, giving rise to errors in measuring. Thirdly, the air separator usually has a large diameter area at the point where it is desired to arrest the surface of the milk at the end of each measurement. Owing to the large area, a small variation in height causes a great variation of volume and consequently an error in the measurement. Fourthly, the termination of measuring is indeterminate and unduly dependent on the actions of the person using the measuring apparatus. The object of the invention is to achieve an improvement in volume measuring procedures known in the art. A more specific object of the invention is to provide a procedure in which the occurrence of spurious errors of measurement can be avoided as closely as possible, and the systematic sources of errors can be avoided or standardized. The objects of the invention are achieved by the aid of a procedure which is mainly characterized in that the pump means, so disposed in relation to the air separator that the air separator is on the intake side of the pump means, is controlled by the aid of a control system so that when the surface of the milk reaches a first higher level in the air separator, the control system has been adapted to switch the pump means to operate at a slow pumping rate, and when the surface of the milk reaches a second level, higher than the first level, in the air separator, the control system has been adapted to switch the pump means to operate at a higher pumping rate. The other characteristic features of the procedure of the present invention are stated in claims 2 and 3. A further object of the invention is to achieve an improvement in volume measuring devices of present art. The more specific object of the invention is to provide a volume measuring means the design and operation of which as closely as possible prevent the occurrence of spurious errors in measuring and inhibit or stabilize the systematic sources of error. A further aim of the present invention is to provide a volume measuring means in which the effect of incorrect operation or deficient functioning or peripherals is minimized. The objects of the invention are achieved by the aid of an apparatus which is mainly characterized in that the pump means is so disposed in relation to the air separator that the air separator is located on the intake side of the pump means and that the pump means is provided with a control system adapted to control the pump so that when the surface of the milk reaches a first higher level in the air separator the pump means is switched to operate at a slow pumping rate and that when the surface of the milk reaches a second level in the air separator, higher than the first level mentioned in the foregoing, the pump means is switched to operate at a higher pumping rate. The rest of the characteristic features of the apparatus of the invention are stated in claims 5 to 10. The procedure and means of the invention represent the insight that the greatest measuring errors are caused by factors other than the volumetric instrument employed. It has thus been understood in the procedure and means of the invention to increase in the first place the efficiency of the separation of air and to improve the stabili- zation of the start and end of the measurement. It has been under¬ stood in the procedure of the invention to separate the air from the milk before the pumping. Consequently, unnecessary mixing of air and milk before the air separation proper is prevented. Secondly, in the procedure of the invention, the air is separated from the milk at a low pressure, that is, at a subatmospheric pressure, whereby the air bubbles present in the milk increase in size and are rapidly separated. Any "micro-bubbles" which may have failed to separate in the air separation process are compressed in the pumping following after the air separation, at a higher pressure and to small volume, whereby their effect on the error of the measurement is quite substantially reduced. In the apparatus of the invention an air separator has been used in which that cross- section area at which the surface of the milk is arrested after completed measuring is small. For this reason, the spurious error due to variations of level remains extremely small. The invention is described in detail referring to an advantegous embodiment of the invention depicted in the figures of the attached drawing, to which embodiment the present invention is not, however, intended to be solely confined. Fig. 1 presents schematically an advantegous embodiment of the means employed in the procedure of the invention. Fig. 2 displays the absolute error observed in a measuring apparatus of prior art, expressed in litres and as per cent error, when the measuring vessel used was a 302 litre measuring vessel. Fig..2b displays the absolute error observed in the measuring appa¬ ratus of the invention, expressed in litres and as per cent error, when for the measuring a 302 litre measuring vessel was used as the measuring vessel. Fig. 3a displays the absolute error observed in a measuring apparatus of prior art, expressed in litres and as per cent error, when * a 40 litre"measuring vessel was used as measuring vessel. "BUR OM Fig. 3b displays the absolute error observed in the measuring appa¬ ratus of the invention, expressed in litres and as per cent error, when a 40 litre measuring vessel was used as the measuring vessel. Fig. 4a displays the absolute error observed in the measuring appa¬ ratus of prior art, expressed in litres and as per cent error, when a 20 litre measuring vessel was used a measuring vessel. Fig. 4b displays the absolute error observed in the measuring appa- ratus of the invention, expressed in litres and as per cent error, when a 20 litre measuring vessel was used as measuring vessel. In the embodiment of Fig. 1 the apparatus of the invention has been generally indicated with reference numeral 10. The apparatus 10 comprises a suction pipe 11, a flexible suction tube 13 provided with shut-off valve 12, and air separator 14, a pump means 18, a volume meter 20 and a check valve 21. The air separator 14 has been provided with a venting means 15, a liquid level sensor 16 and a pressure pick-up 17. The reference numeral 22 indicates a control means, adapted to control the operation of the air separator 15. The signals from the liquid level sensor 16 and the pressure pick-up 17 are conducted to the control means 22. The pump means 18 is advantageously a centrifugal pump disposed to be controlled by a hydraulic control system 23 in accordance with the control signal from the control means 22. The reference numeral 19 indicates a filter inserted in the pipeline between the pump means 18 and the volume meter 20. The operation of the means 10 according to the present invention is as follows. Before starting the measurement, the shut-off valve 12 is closed while the hydraulic pump connected to the engine of the vehicle is in operation and the apparatus 10 is filled with milk forward from the level A of the air separator 14 in the direction of milk flow. The person conducting the measurement switches the apparatus 10 on with the aid of a switch on the control means 22. The pressure pick-up 17 transmits the pressure prevailing in the air separator 14. If the pressure in the air separator is higher than the predetermined limit pressure which is lower than the atmospheric pressure, the venting means 15 is switched on and extracts air from the air separator 14. The person conducting the measurement connects the flexible suction tube 13 to the farm tank and opens the bottom valve of the farm tank or, in milk can collection, attaches the suction pipe 11 and pushes the suction pipe 11 into the milk can and opens the shut-off valve 12, whereby milk begins under action of differential pressure to flow into the air separator 14. The venting means 15 continuously evacuates air entering the air separator 14, at the same time drawing more milk into the air separator 14. When the surface of the milk reaches the level B in the air separator 14, the pump means 18 is switched on at "a slow pumping rate", which is higher than or equal to the minimum flow rate allowed for the volume meter 20. It should thus be noted that in the means 10 of the present invention the pump means 18 has been so disposed in relation to the air separator 14 that the air separator 14 is located on the intake side of the pump means 18. When the surface of the milk in the air ' separator 14 reaches the level C, the pumping means 18 is switched on to "the full pumping rate" and the venting means 15 stops the elimination of air. If no air is now entrained with the milk, the operation of the apparatus 10 of the invention continues in this state. If air in the milk enters the air separator 14, the air is separated to be in the top part of the air separator 14 and at the same time the pressure in the top part of the air separator 14 increases, whereby the increased pressure of the air pushes down the surface of the milk in the air separator 14. When the surface of the milk in the air separator 14 falls below the level C, the venting means 15 starts to evacuate air until the surface of the milk in the air separator 14 again reaches the level C. When the milk surface again * reaches the level C in the air separator 14, the venting means 15 stops. If the entrance of milk into the air separator 14 totally stops e.g. when the farm tank is exhausted, the surface of the milk goes down in spite of continuous air venting, first to the level B, whereby the pumping means 18 is switched to "the slow pumping rate", and 5 further to the level A, whereby the pump means 18 stops. The volume of the milk drawn that has flown through the apparatus 10 can be read from the volume meter 20. In the procedure of the invention the control of the pump means 18 10 at two different pumping rates is substantial. It is further essential to extract air by utilizing subatmospheric pressure. An advantageous embodiment is that in which the subatmospheric pressure required for air extraction is provided by using the compressed air of the brake system of a car. Furthermore, a 15 characteristic feature of the procedure of the invention is the manner in which subatmospheric pressure is maintained in the air separator 14. The air separator 14 is further advantageously designed to be conical so that the air separator 14 conically tapers downwards, whereby a highly accurate termination volume is 20 obtained. With the aid of the procedure and means 10 of the invention a high accuracy of measurement is achieved, as shown by the results of comparison presented in Figs 2a and 2b, respectively 3a and 3b, 25 respectively 4a and 4b. The calibration of the volume meter was performed in these comparative measurements with water at the flow rate of 300 litres per minute. The measuring vessels has capacities of 302, 40 and 20 litres. The raw milk had been quieted during two hours and its temperature was 3-4 C. The actions of the person 30 conducting the measurements were similar to those in normal suction gathering measurement. On the whole, all steps had been standardized in general both in the measurements with the measuring apparatus of prior art and in those with the measuring apparatus 10 of the invention. 35 As the errors displayed in Figs 2a and 2b, respectively 3a and 3b, and 4a and 4b, expressed in litres and as per cent error indicate, a quite substantially better measuring accuracy is reached with the apparatus 10 of the invention. It can be deduced from the results of measurement that the means of the measured values reveal the systematic errors caused by the air venting. Secondly, the individual variations between results of measurement indicate the random errors. Such random errors are the volume variations incurred at the start and termination. It should further be noted that any small measured quantities are only pumped at the "slow flow rate", which causes about 0,1% higher calibration, according to the caharacteristic curve of the volume meter 20. This is believed to account for the difference between the means found with small and large measured quantities. In the foregoing only one advantageous embodiment of the invention has been disclosed, and it is obvious to a person skilled in the art that numerous modifications are feasible within the scope of the inventive idea stated in the claims following below.

Claims: Claims 1. Procedure in milk gathering from milk producers taking place with the aid of tank cars, for volume measuring of milk, wherein milk is conducted through a flexible suction tube (13) or through a suction pipe (11) and a flexible suction tube (13) to an air separator (14) and from the air separator (14) to a volume meter (20), characterized in that a pump means (18), so disposed with reference to the air separator (14) that the air separator (14) is on the intake side of the pump means (18) , is so controlled with the aid of a control system (23) that when the milk surface reaches in the air separator (14) a first upper level (B) the control system (23) has been adapted to switch the pump means (18) to operate at a slow pumping rate, and that when the milk surface in the air separator (14) reaches a second level (C) higher than the said first upper level (B) the control system (23) has been adapted to switch the pumping means (18) to operate at a higher pumping rate. 2. Procedure according to claim 1, characterized in that the air entrained with the milk is separated in the air separator (14) utilizing subatmospheric pressure in that an air venting means (15) is connected to operate when the pressure in the air separator (14) is higher than a predetermined limit pressure (P ) , which is lower than the atmospheric pressure. 3. Procedure according to claim 2, characterized in that the sub- atmospheric pressure required for air separation is produced by using the compressed air of the tank car's brake system. 4. Means in milk gathering from milk producers accomplished with the aid of tank cars, said means (10) comprising a flexible suction tube (13) or a suction pipe (11) and a flexible suction tube (13), an air separator (14) provided with a venting means (15) , a pump means (18) and a volume meter (20), and the milk being drawn with said means from the farm tank or from a milk can into the air separator (14) , whence the milk is further conducted to the volume meter (20) , characterized in that the pump means has been so disposed in OM 10 relation to the air separator (14) that the air separator (14) is located on the intake side of the pump means (18), and that the pump means (18) has been provided with a control system (23) adapted to control the pump in such manner that when the milk surface in the air separator (14) reaches a first upper level (B) the pump means (18) is switched on to operate at a slow pumping rate, and that when the milk surface reaches in the air separator a second upper level (C) higher than the said first upper level (B) the pump means becomes switched to operate at a higher pumping rate. 5. Means according to claim 4, characterized in that the means (10) has been provided with a control means (22) adapted to control the operation of the venting means (15) in such manner that the venting means (15) is connected to operate when the pressure in the air separator (14) exceeds a predetermined limit pressure (P ) , which is lower than atmospheric pressure. 6. Means according to claim 5, characterized in that the air separator (14) has been provided with a pressure pick-up (17) adapted to signal to the control means (23) the pressure pre¬ vailing in the air separator. 7. Means according to any one of claims 4 to 6, characterized in that the control system (23) has been adapted to stop the pump means (18) when the milk surface falls below a lowest level (A) in the air separator. 8. Means according to any one of claims 4 to 7, characterized in that the control system (23) is a hydraulic control system. 9. Means according to any one of claims 4 to 8, characterized in that the air separator (14) is conically tapering downward. 10. Means according to any one claims 4 to 9, characterized in that the air separator (14) has been provided with a liquid level sensor (16) adapted to signal to the control means (22) the milk surface level in the air separator (14) . OMPI

Inventors: KUJALA HANNU, SANTASALO HANNO, KUJALA, HANNU, SANTASALO, HANNO
Applicants: OT TEHDAS OY, OT-TEHDAS OY
Application year: 1982
Main classification: B67D5
IPC codes: A01J5, G01F15