Fluid transfer coupling

A coupling for conveying a fluid from a source and thence between a stationary part and a rotatable part having confronting ports centered on a rotation axis of the rotatable part, the coupling comprising:

• an axially extending tube fixed in the port of the stationary part and extending toward the port of the rotatable part;
• a control sleeve axially slidable on and coaxially surrounding the tube;
• a first slide ring fixed to the control sleeve and carrying a seal ring turned toward the port of the rotatable part;
• a second slide ring on the rotatable part at the port thereof and axially engageable with the first slide ring, the tube, control sleeve, first ring, and second ring together forming an axially throughgoing passage for the fluid;
• seals engaged between the stationary part, the tube, and the control sleeve and forming an annular and pressurizable chamber around the tube, separate from the passage, and in which an axially directed and annular end face of the axially slidable control sleeve is exposed, whereby pressurization of the chamber presses the slide rings axially against each other;
• and
• means for applying fluid pressure to the chamber and thereby varying the axial pressure with which the first slide ring bears axially on the second slide ring.