10 the sleeve 2 has an axial extension 2a extending from a shoulder 2b the flat spring 4 is provided with a central bore 4a which receives the axial extension 2a of the sleeve 2 a second ring 5 is provided with a central bore 5a and is also telescopically received on the axial extension 2a of the sleeve 2 so that the flat spring 4 is sandwiched between the ring 5 and the shoulder 2b a plurality of screws 50 hold the ring the spring and sleeve 2 together in a fixed arrangement the sleeve 2 also has a second shoulder 2c axially spaced from the shoulder 2b and the ring 5 has an annular shoulder 5b axially spaced from the surface of the ring 5 engaging the spring 4 the spacing between the shoulder 5b and the shoulder 2c is such that the assembly formed by the ring components 3a and 3b will have as illustrated an axial clearance x between a surface of the components 3a and the shoulder 5b as well as between the shoulder 2c and the component 3b this clearance enables the components to be shifted appropriately one with respect to the other in the axial direction the elasticity of the flat spring 4 depends on its structure its shape its.