THE INFLOW OF MILK INTO THE SEPARATOR-DRUM. 123 



Just as milk, standing in a milk-pan at rest, exercises a pressure 

 on the bottom and sides of the pan, due to the force of gravity, so 

 precisely milk, in a separator-drum in motion, exercises a pressure 

 on the sides of the drum, which is caused by centrifugal force, and 

 which is proportional to the strength of that force. 



In the same way, just as in milk, standing in a milk-pan at rest, 

 the fatty globules move upwards, in a direction opposite to that in 

 which gravity acts, so the fatty globules in a separator-drum, filled 

 with milk and in motion, travel in a direction opposite to that of 

 centrifugal force, that is, from outside to inside. In this case, as in 

 the former case, the layer of cream rises to the surface, which in the 

 separator-drum is that portion nearest to the axis of revolution. 



57. The Inflow of Milk into the Separator-drum. The drums of 

 many of the older separators suffered from this disadvantage, viz. 

 that the milk, flowing into them when revolving, was led in on the 

 top of the cream layer, through which it naturally at once sank 

 on account of its high specific gravity. This influenced the amount 

 of fat obtained. Nearly all the drums of the newer separators are 

 so arranged that the milk flowing into them is led in by a suitable 

 arrangement to the inside of the circle of milk, and in this way the 

 very considerable force with which it has to press through the layer 

 of cream is avoided, and the full yield of fat is thereby obtained. 



58. The Outflow of Cream and Skim -milk from the Separator- 

 drum. The outflow of the liquid from a filled separator-drum in 

 motion takes place with considerable energy, and is due to the 

 driving power employed, being in no way connected with the centri- 

 fugal force. This force is greater the further the spot is from the 

 revolving axis. Its amount is proportional to the square of the 

 rapidity of the revolving motion at this place, and increases, in a 

 simple regular proportion, with the radius vector of the spot of 

 outflow. In order, therefore, to reduce as far as possible the force 

 with which the liquid flows out, and thus to effect a saving in 

 motive power, the exit for the outflow of cream and skim-milk is 

 chosen as near the revolving axis as can be. The exit for the cream 

 can be placed directly on the surface of the ring of milk, that is to 

 say, as near as it can possibly be to the axis; whereas the exit for the 

 outflow of skim-milk, on account of the higher specific gravity of this 

 liquid, must be placed slightly further back. The skim-milk is con- 

 ducted either by means of tubes, which run back to the wall of the 

 drum to the surface of the milk-ring, or by means of a special space 



