Patent ID: 7891275

Claim:
An adapter coupling device comprising: an adapter having a polygonal recess defined therein for receiving a bit therein, a first radial hole and a second radial hole defined in an outer periphery thereof, a first bead received in the first radial hole and a second bead received in the second radial hole, a circular recess defined in an inner end of the polygonal recess, a first spring and a positioning block received in the circular recess, the positioning block having a receiving space defined radially in an outer periphery thereof and the receiving space located corresponding to the second radial hole, the positioning block having an outer surface, the positioning block including a top ring, a magnet and a base, the top ring mounted on the magnet which is engaged with the base, the base including a passage defined therethrough and the first spring received in the passage and contacting an underside of the magnet, the receiving space being defined between the top ring and the base, the outer surface extending from a top of the base, and an outer sleeve mounted to the adapter and a second spring mounted to the adapter and engaged with the outer sleeve, the second spring providing a force to return the outer sleeve relative to the adapter, an annular groove defined in an inner surface of the outer sleeve and located corresponding to second radial hole of the adapter, an inclined inner surface defined in the inner surface of the outer sleeve and the inclined inner surface having a maximum inclination of 30 degrees relative to an axis of the outer sleeve, the inner surface of the outer sleeve pushing the second bead into the receiving space of the positioning block or the outer surface of the positioning block pushing the second bead out from the receiving space to positioning the outer sleeve.