Power tool

1. A power tool comprising a housing, a motor housed in the housing, and a handle formed on the housing, the handle being provided with a speed regulating mechanism for adjusting the rotational speed of the motor, and a speed limiting mechanism cooperating with the speed regulating mechanism, wherein said speed limiting mechanism comprises a first knob and a second knob disposed on two sides of the handle, said first knob is provided with a rib member protruding toward the second knob and a slot formed on the rib member, and said second knob is provided with a connecting structure protruding into the rib member and a bar protruding outwardly from the connecting structure, said bar being latched and received in said slot, so that said first knob and said second knob are interlocked with each other to be toggled to limit said motor to operate at a fixed rotational speed.

2. The power tool according to claim 1 , wherein said rib member comprises a first arm disposed in an arc shape, a second arm spaced apart from the first arm, and a third arm disposed in a straight line connecting the first arm and the second arm, said first arm, said second arm and said third arm cooperate with each other such that a cross section of the rib member is D-shaped, and said slot is disposed on said third arm.

3. The power tool according to claim 2 , wherein said connecting structure is disposed in a D-shape, and said bar is formed to protrude outward from a straight side of the D-shaped connecting structure.

4. The power tool according to claim 2 , wherein said speed limiting mechanism further comprises a micro switch housed in said handle and located beside said second knob, and said second knob is further provided with a push rod formed from said connecting structure protruding outwardly, and when said push rod triggers said micro switch, said motor runs at a maximum speed.

5. The power tool according to claim 4 , wherein said speed limiting mechanism further comprises a torsion spring for engaging said first knob, said first arm of said first knob comprising a limiting arm protruding in a radial direction of said first knob, and when the push rod triggers the micro switch, one of the swing arms of the torsion spring is fixed to the housing, and the other swing arm of the torsion spring pressing against said limiting arm.

6. The power tool according to claim 1 , wherein said speed regulating mechanism comprising a speed regulating switch for adjusting the rotational speed of said motor, and a switch trigger coupled with said speed regulating switch and pivotally mounted on said handle, said speed regulating switch is provided with a pressing portion, and said switch trigger comprises a pivoting portion mounted on said handle, and a push arm and an abutting arm located on both sides of said pivoting portion which rotates around the pivoting portion, said abutting arm abuts said pressing portion to adjust the rotational speed of said motor.

7. The power tool according to claim 6 , wherein said pivoting portion is a shaft hole, and said handle is provided with a pivoting shaft that cooperates with said shaft hole.

8. The power tool according to claim 1 , wherein said housing comprises a first housing coupled to said first knob and a second housing coupled to said second knob, said speed regulating mechanism is received in a receiving cavity defined by said first housing and said second housing.

9. The power tool according to claim 8 , wherein a first positioning portion is disposed on a side of said first knob toward the first housing, and a second positioning portion is disposed on said first housing, said first positioning portion and said second positioning portion cooperate with each other such that said first knob switches and keeps constant speed between three speed positions.