Patent ID: 8307735

Claim:
A bicycle stem comprising: a steerer tube base including a pivotal end having a pivotal hole and two blocking devices provided in the pivotal end and protruding from an inner side of the pivotal hole; a clamp arm including a coupled end pivotally coupled to the pivotal end; and a lock unit, which is operable between a first position and a second position, including two lock sleeves, an engaged bolt operably rotated and disposed in the pivotal hole of the pivotal end and rotatably engaging the two lock sleeves, and a blocking element for preventing the engaged bolt detaching from the pivotal end, with the blocking devices respectively preventing the two lock sleeves completely inserting into the pivotal hole of the pivotal end, wherein the two lock sleeves rotate simultaneously upon operation of the engaged bolt; wherein each lock sleeve includes a through-hole engaged with an end of the engaged bolt and an outer toothed surface engaged with the pivotal hole of the pivotal end and the coupled end; wherein in the first position of the lock unit, the lock sleeves are engaged with the pivotal hole of the pivotal end and the coupled end of the clamp arm simultaneously, with the steerer tube base fixed and the clamp arm being not able to pivot with respect to the steerer tube base; and wherein in the second position of the lock unit, the engaged bolt rotates with respect to the pivotal end and drives the lock sleeves to disengage from the pivotal hole of the pivotal end, with the clamp arm able to be driven to pivot with respect to the steerer tube base to a desired position.