Rotary indexing device

A rotary indexing device comprising:

• a housing including an inner cylinder and an outer cylinder which are concentrically arranged at a radial space therebetween;
• an output shaft having a hollow cylinder rotatably supported by the outer cylinder of said housing via bearings, a portion of said hollow cylinder being concentrically arranged within the radial space of said housing;
• an indexing drive motor having a motor stator fixed inside the housing and a motor rotor fixed on the output shaft and provided coaxially with said motor stator;
• a rotational angle detector for detecting the rotational angle of the output shaft relative to the housing;
• a rotation indexing table fixed to an end of the output shaft;
• and
• a clamp device having a clamping sleeve arranged in the radial space between perimetric faces of the output shaft and the housing, a middle portion of the sleeve in an axial direction being opposed to one face of the perimetric faces across a narrow interstice, both ends of the sleeve being secured in an airtight manner to the other face of the perimetric faces, and being formed with a large number of slits on said middle portion to communicate an inner and an outer region therefrom, an annular elastic member which covers said large number of slits of the sleeve to form a pressurizing chamber with said other face of the perimetric faces, and a fluid path to feed pressurizing fluid into said pressurizing chamber, said clamping sleeve being deformed radially to cause said narrow interstice to vanish and press onto said one face of the perimetric faces with the pressurizing force from said pressurizing chamber, thereby causing the clamping of the output shaft against the housing.