US Patent 7108245 Jack having safety effect

A jack includes a base provided with a plurality of catch blocks, a lift arm pivotable relative to the base, and a safety member pivotally mounted on the lift arm to move therewith. Thus, when the lift arm is lifted, the first end of the safety member is locked on either one of the catch blocks of the base, so that the safety member is fixed by the base during upward movement of the lift arm so as to fix the lift arm, thereby preventing the lift arm from being lowered too quickly when the power supplied to the lift arm disappears accidentally due to malfunction so as to provide a safety effect.