Mechanism for adjusting a rotational position of a table of power miter saw

1. A power miter saw comprising:

a base including a plurality of positioning apertures;

a table rotatably mounted on the base and including an arm projecting forward;

a saw blade and motor mechanism configured to rotate a circular saw blade thereof;

a pivotal positioning seat interconnecting two linear guide mechanisms and a support seat at a rear end of the base;

a connecting seat interconnecting the linear guide mechanisms to the saw blade and motor mechanism;

a locking device including a knob disposed on a rear end of the arm, a first face cam disposed under the arm, a first rod interconnecting the knob and the first face cam, a first biasing member disposed on the first face cam, a second face cam disposed under the arm and proximate the first face cam, a locking assembly pivotably disposed under the arm and including a hole, a projection, a second biasing member put on the projection and having one end urging against an inner surface of the arm and the other end urging against a joining portion of the projection and the locking assembly, and a knurled surface, a second rod having one end secured to the second face cam and the other end fastened in the hole; and

a positioning device including a spring biased push button disposed on one side of a rear portion of the arm, a button member disposed on a top of the rear end of the arm, a lever having two side pins pivotably secured to two sides of the arm respectively, and a hole member disposed on one side of a forward portion, two parallel links each pivotably interconnecting the button member and a forward end of the lever, and a resilient, bifurcated positioning member having a forward end rested upon a rear bar of the lever, two rear ends secured to the arm, and a protrusion projecting downward;

wherein in a locked state, the first face cam is disengaged from the second face, the second biasing member is compressed, an annular edge of the base is urged against by the knurled surface, the protrusion is disposed in a predetermined one of the positioning apertures, the lever is not capable of pivoting, and the button member is irresponsive to a pressing exerted thereon.

2. The power miter saw of claim 1 , wherein the positioning apertures are arranged as a curve adjacent to a periphery of the base.

3. The power miter saw of claim 1 , wherein the second rod has one end secured to the second face cam, and further comprising a rod-shaped receptacle having one end for receiving a portion of the threaded other end of the second rod and the other end fastened in the hole, and a fastener threadedly put on the remaining portion of the threaded other end of the second rod.

4. The power miter saw of claim 1 , wherein for adjusting a rotational position of the table in a first mode the following are performed:

pressing down the button member to lower and align the hole with an end of the push button and pivoting the rear bar of the lever upward to lift the forward ends of the positioning member to disengage the protrusion from the positioning aperture;

rotating the table a predetermined angle until a desired position of the table is reached;

releasing the button member to fall the protrusion into one of the positioning apertures; and

clockwise rotating the knob to disengage the first face cam from the second face cam and move the second face cam rearward to engage the knurled surface with the annular edge of the base and the second spring being compressed, thereby fastening the base and locking the table.

5. The power miter saw of claim 1 , wherein for adjusting a rotational position of the table in a second mode the following are performed:

pressing down the button member to lower and align the hole with an end of the push button and pivoting the rear bar of the lever upward to lift the forward ends of the positioning member to disengage the protrusion from the positioning aperture;

pushing the push button to compress the third spring until the push button's stepped-diameter shank passes through the hole with both the push button and the lever being locked;

rotating the table with the protrusion disposed above the positioning apertures until a desired one of the positioning apertures is reached; and

clockwise rotating the knob to disengage the first face cam from the second face cam and move the second face cam moves rearward to engage the knurled surface with the annular edge of the base and the second spring being compressed, thereby fastening the base and locking the table.