Lockable swivel coupling

In a lockable swivel coupling comprising two machine elements, a journal means on one of the elements, a hole means in the other of the elements, receiving the journal means, the journal means and the hole means having rotational-symmetric complementary gliding surfaces forming a guide for swivelling motion between the two elements about a swivelling axis which also constitutes a common axis for the hole means and the journal means, and locking means for rigidly locking the elements in different swivelling positions, the improvement comprising:

• that the complementary gliding surfaces are conical along at least part of their axial extensions;
• that the journal means has an end surface cooperating with a complementary bottom surface in the hole means, the journal means being axially form-locked in the hole means with small axial clearance;
• and the locking means comprises an integral leak-proof working chamber behind at least one of said conical surfaces, the end surface and the bottom surface, the chamber having a flexible wall defining said one surface, the working chamber communicating with a hydraulic pressure source, whereby a hydraulic pressurization of the chamber causes a rigid locking of the elements against swivelling relative to each other with retained angular attitude and a precise axial positioning of the elements relative to each other.