Method and apparatus for changing spacers

A device for mixing two materials, comprising:

• a housing (2) with at least a first opening (5) for feeding a first material and a second opening (6) for feeding a second material, a conical part (15), and a discharge opening (8) for discharging the first and second materials as a mixture, the discharge opening (8) being located at an end part of the conical part (15) of the housing (2);
• a mixing element (3) received in the housing, the mixing element (3) having an axis extending along a first direction, the mixing element (3) being rotatable around the first direction of the axis, the mixing element (3) having a cylindrical area (9) adjacent a conical part (14), the cylindrical area (9) including grooves, there being a gap (18) between the conical part (14) of the mixing element (3) and the conical part (15) of the housing (2) and in an area in front of the discharge opening (8);
• first ribs (12) extending from an inner surface (10) of the housing (2) toward the cylindrical area (9) if the mixing element (3);
• and
• second ribs (11) set in the grooves of the cylindrical area of the mixing element (3), the second ribs extending from the cylindrical area (9) towards the inner surface (10) of the housing (2), the second ribs extending towards the inner surface (10) of the housing (2) between adjacent ones of the first ribs (12), wherein,
• along the cylindrical area (9), axially inner end portions of the first ribs overlap axially outer end portions of adjacent second ribs in the first direction of the axis, each second rib has an axially inner portion closest to the axis (7) that is spaced apart and separated from an inner portion of the groove in which the second rib is set,
• the first and second openings (5, 6) are arranged in an area where the second ribs (11) extend from the cylindrical area (9) towards the inner surface (10) of the housing (2),
• the mixing element (3) is adjustable to advance in the first direction of the axis (7) in relation to the housing (2) for adjusting the size of the gap (18) between the conical part (14) of the mixing element (3) and the conical part (15) of the housing (2), the mixing element (3) being adjustable, by movement in the first direction of the axis during rotation about the axis, until the gap is closed and the discharge opening (8) of the housing (2) is also closed thereby closing the discharge opening (8) of the housing (2).