1. Field of the Invention This invention relates to a method and an apparatus for taking out an average milk sample proportional to the yield obtained in the milking of a cow.
The milk is transported from the cow's teats by means of vacuum. The measuring apparatus is inserted in the tube leading from the teat cups to the milk line, from which the milk is sucked into the collection tank.
To facilitate the transport of the milk from the milking unit to the milk line and further to the tank without excessive vacuum drop the milking unit is provided with vent hole through which a suitable quantity of air is sucked in together with the milk, normally of the order of 10 liters of air per minute. On completion of the milking, large amounts of false air will often enter at the teats on account of their getting slack. These amounts may often be considerably above for instance 10 liters per minute.
Cows milk at widely different rates, varying from nought to about 10 liters of milk per minute. The milking rate varies (drops) during the milking process.
Apparatus for measuring the milk yield of a cow are generally arranged to draw off a sample during the milking which is approximately proportional to the amount of milk flowing through the system. By measuring the quantity of the sample it will thus be possible to determine the amount of milk that has passed through the apparatus, i.e. the yield obtained from the cow who has been milked. The measurement of the quantity of the sample is generally performed volumetrically by the reading of the scale of a cylindrical tube in which the sample is collected.
2. Description of Prior Art
A proportional sampling from the passing milk may be performed in several ways, but in a conventional procedure used in several types of apparatus the inflowing milk is distributed evenly over a surface, for instance the internal surface of a cylindrical chamber. Such an apparatus is known for instance from the specification of British Pat. No. 1,095,708. Part of the milk distributed in the chamber is received of a funnel the transverse area of which is a certain fraction of the entire transverse area of the cylindrical chamber, and from this funnel the milk sample flows into the metering cylinder where the yield can be read on a scale. The measuring accuracy is determined by the uniformity with which the milk flow is distributed over the internal surface of the cylindrical chamber.
A high milking rate and a low content of air in the milk will give an ample filling of the apparatus and consequently an even distribution of milk over the spreading surface.
Problems of measuring accuracy will arise specifically when the milking rate is low and considerable amounts of air are transported with the milk in consequence of the said influx of false air. In certain milking systems the air intake in the milking unit is considerable. Where such a milking system is combined with slowly milking cows the reading of the apparatus will be too low (about 10-15%, dependent on conditions).