Abstract: The change head (1) for a tool change apparatus is provided at its free end with a prism-shaped centering opening (15) and in the center thereof an axially displaceable screw driver (3). Arranged concentrically with respect thereto is a screwthreaded sleeve (9) which has a female screwthread and which is mounted slidably but non-rotatably in an axial bore (8) in the head (1) and which is urged towards the centering opening (15) by a spring (14). A respective radially displaceable clamping member (12) is provided in each of two radially extending bores (11) in the screwthreaded sleeve (9), the two radial ends of each clamping member being cones (12a, 12b) (or hemispheres).

Abstract: An artificial skiing surface comprising a plurality of single elements formed from plastic adapted to be detachably joined together in side-by-side relationship including a base layer provided with a plurality of flexible upwardly extending plastic fingers and a plurality of sockets in each of which rotatable balls are disposed formed from plastic having a hardness greater than that of the fingers and having the same height as that of the fingers together with a guidance comb inserted in a groove in the base layer and having flexible teeth with globular tips which extend upwardly preferably to a height above that of the fingers to provide control of a ski sliding thereon.