Abstract: The present invention relates to a mixer for mixing two fluids, the mixer comprising a power source (5) with a rotating transmission shaft (7), a hollow rotor (6) to be submerged in a first fluid (8) and arranged to rotate with the shaft, wherein at least one end of the rotor comprises an opening or openings for supply of a second fluid (9) to the hollow rotor (6), and jet openings (10) are provided in the side surface of the rotor through which the second fluid (9) is discharged into the first fluid (8) surrounding the rotor. To achieve a better operating efficiency, the mixer has a tight liquid seal (14) shaped to cover and isolate substantially the entire portion of the rotor that is above the first fluid.

Abstract: The invention relates to a power supply and control unit for a light system, especially an airport approach light system, for making a number of lights go on and out as a progressive light front. The invention is also concerned with a lighting unit (1) suitable for use in combination with this power supply and control unit.

Abstract: This invention is related to a method and device for measuring the distance (.delta.) between the discs of a refiner, in which method a magnetic field is generated by means of a coil (5) placed at one disc (4), which magnetic field is allowed to run at least partly through the other disc (3). According to the invention the measuring is carried out by using the actual distance between the refiner discs as the object of measuring in that the magnetic flux over the distance between the discs caused by the coil (5), which is formed at least at one refiner-disc tooth (7) or comparable element, is measured such that the flux running over the distance between two opposite teeth (7,8) is detected by means of another coil (6), such as is formed round at least either of said teeth, the signal induced in the coil being interpreted as a quantity that expresses the distance (.delta.) between the teeth.