Handheld power tool and impact block return device thereof

A handheld power tool, having a main body, a nail magazine, an impact block, and an impact block return device, the main body having an exit at one end thereof, the exit communicating with the nail magazine and the impact block return device, the main body having a compressed air chamber at the other end thereof, the compressed air chamber accommodating the impact block, the impact block having a plurality of continuous teeth arranged along a lengthwise direction of the impact block, the impact block return device comprising:

• a gearwheel adjacent to and engaged with the teeth of the impact block;
• a ratchet wheel connecting to the gearwheel and rotating simultaneously with the gearwheel;
• and
• a clamping member disposed at a position corresponding to the ratchet wheel and located away from the teeth of the impact block, the clamping member being operated in a first state and a second state, the clamping member contacting the ratchet wheel in the first state and the clamping member being separated from the ratchet wheel in the second state;
• wherein the impact block only can do a single-directional movement when the clamping member contacts the ratchet wheel in the first state.