Patent ID: 8746421

Claim:
A blocking device ( 30 ) for blocking a rotary motion of a shaft ( 14 ) relative to a housing ( 16 ) of a gear-drive unit ( 10 ) in a blocking state, the blocking device ( 30 ) having a first blocking element ( 32 ) and a second blocking element ( 34 ), where the second blocking element ( 34 ) is displaceable relative to the first blocking element ( 32 ) using an electromagnet ( 44 ) and a restoring element ( 42 ), wherein the blocking elements ( 32 , 34 ) each have radially extending indentations ( 82 ) and radially extending raised areas ( 84 ), positioned about an outer radial surface portion proximate each blocking element's circumferential edge, wherein each radially extending indentation and raised area pair on one blocking surface is positioned to oppose each radially raised area and extending indentation pair on the other blocking surface, enabling the blocking elements to mesh with one another in an axial direction and in a form-locking fashion to block the rotary motion of the shaft ( 14 ) in the blocking state, wherein the blocking device ( 30 ) is embodied as a separate, independent structural unit ( 31 ) comprising a barrier housing ( 52 ) configured as a stop disk ( 60 ) forming at least one axial stop ( 74 ) for the first blocking element ( 32 ), which barrier housing ( 52 ) is mounted as a separate independent structural unit ( 31 ) to the housing ( 16 ), wherein the first blocking element ( 32 ) is embodied as a rotatable disk with a central opening ( 64 ), an inner toothing ( 68 ) configured to engage corresponding outer toothing ( 70 ) of a slaving means ( 66 ) first secured to the shaft ( 14 ), which shaft ( 14 ) with slaving means ( 66 ) is then thrust into the blocking element ( 32 ) in a manner fixed against relative rotation to effect installation in a way that axial positioning of the drive shaft relative to the blocking device is not vulnerable to tolerances; and wherein the first blocking element ( 32 ) includes axial extensions ( 62 , 61 , 63 ) that form a detent hook ( 61 ).