Driver

1. A driver comprising:

a nose portion provided in a housing and extending in a longitudinal direction, the nose portion being configured to allow a fastener to pass therethrough;

a plunger configured to move in an impact direction parallel to the longitudinal direction to impact the fastener through the nose portion;

a weight; and

a resilient member configured to be compressed by a motor in the longitudinal direction, a release of the compression in the resilient member causing the plunger to move in the impact direction, while causing the weight to move in a counter-impact direction which is away from the plunger, and

a drive mechanism configured to cause the motor to compress the resilient member in the longitudinal direction, the drive mechanism including a first gear and a second gear meshingly engaged with the first gear, the first gear and the second gear being configured to be rotated by the motor, each of the first gear and the second gear being provided with a plurality of roller-cams arranged in a circumferential direction at predetermined intervals, wherein

the resilient member is provided between the plunger and the weight, the resilient member having one end portion and another end portion in the longitudinal direction, the one end portion being configured to urge the plunger, and the another end portion being configured to urge the weight, wherein

rotation of the first gear and the second gear causes the plurality of roller-cams of the first gear to be in abutment with one of the plunger and the weight, while causing the plurality of roller-cams of the second gear to be in abutment with an other of the plunger and the weight, thereby compressing the resilient member in the longitudinal direction.

2. The driver according to claim 1 , wherein the resilient member comprises a single coil spring.

3. The driver according to claim 1 , wherein

the drive mechanism is configured to release compression of the resilient member to cause the plunger to start moving in the impact direction, and simultaneously cause the weight to start moving in the counter-impact direction.

4. The driver according to claim 1 , wherein

the drive mechanism is configured to release compression of the resilient member from the another end portion to cause the weight to start moving in the counter-impact direction, and then the drive mechanism is configured to release compression of the resilient member from the one end portion to cause the plunger to move in the impact direction.

5. The driver according to claim 1 , further comprising a weight restriction member provided in the housing and configured to restrict further movement of the weight in the counter-impact direction, wherein

the weight is configured to be in abutment with the weight restriction member after the plunger strikes the fastener.

6. The driver according to claim 5 , further comprising a plunger restriction member provided in the housing and configured to restrict movement of the plunger in the impact direction, wherein

the plunger and the weight are provided in the housing in such a manner that a moving distance of the plunger to the plunger restriction member is set longer than a moving distance of the weight to the weight restriction member.

7. The driver according to claim 1 , wherein each of the plurality of roller-cams of the first gear has a protruding length in an axial direction, the protruding length of each roller-cam of the first gear being different from each other, and each of the plurality of roller-cams of the second gear has a protruding length in an axial direction, the protruding length of each roller-cam of the second gear being different from each other.