Overload coupling device

In an overload coupling device for thread-cutter chucks or quick-change inserts therefor, comprising a cylindrical sleeve loadable with the rotational drive moment, a drive shank drivable by said drive sleeve and held coaxially and rotatably within said sleeve;

• a spring-loaded ball-pocket coupling with adjustable tripping torque positioned in a force transmission flux between said drive sleeve and said drive shank and including a plurality of coupling balls which couple said drive shank with said drive sleeve, said drive sleeve being formed with a plurality of cage slots which are inwardly and outwardly open in a radial direction and which are open in an axial direction on axial end faces thereof, said cage slots each receiving one of said coupling balls, the angular width of said cage slots being at least as great as the diameter of each coupling ball, said drive shank having a peripheral surface facing said drive sleeve and being formed at said peripheral surface in the axial regions of said cage slots with recessed ball-pockets spaced from each other at equal angular intervals in a circumferential direction, said ball-pockets being of a depth smaller than the diameter of the coupling ball and adapted for receiving said coupling balls;
• a cylindrical closure sleeve coaxially surrounding said drive sleeve and held on said drive sleeve with a formation therebetween of an annular space;
• a thrust ring arranged in said annular space on an axial side of said coupling balls, said thrust ring being adjustably supported by thrust springs axially in the direction towards said cage slots and being pressable against said coupling balls, said cage slots being substantially inclined towards a working drive direction of said drive sleeve, said closure sleeve having in the axial region of said cage slots in an interior an annular groove the bottom of which extends at a radial distance corresponding at least to the diameter of the coupling ball from said peripheral surface of the drive shank, the improvement comprising said cage slots being arranged in the circumferential direction of said drive sleeve in pairs and following closely adjacent one after another, one cage slot in a pair having an angular width which is substantially as great as the diameter of the associated coupling ball, and another cage slot in the pair, which follows closely adjacent said one cage slot, having an angular width which is substantially greater than the diameter of the associated coupling ball;
• and an annular elastic element arranged in the annular space between the closure sleeve and the drive shank, said elastic element, in operation of said ball-pocket coupling exerting on the respective coupling ball radially displaced from the associated ball pocket into said annular groove and positioned between said peripheral surface of said drive shaft and said annular groove of said closure sleeve a prestressed radial force.