Trigger valve apparatus for pneumatic tool

1. A pneumatic tool comprising a circular cylinder, a piston slidably accommodated in said circular cylinder, a driver blade integrally fanned with said piston, and a sleeve valve portion for driving said piston when compression air is discharged from a sleeve valve chamber via a trigger valve portion, wherein

said trigger valve portion father comprising:

a plunger shifting in response to a trigger operation by a user;

a valve piston slidably supporting said plunger and shifting in a direction opposed to a shifting direction of said plunger; and

a valve bush slidably supporting said plunger and said valve piston so as to allow slide movements of said plunger and said valve piston, and

a seal member provided on a first surface formed on one of said valve piston and said plunger; and

combined grooves and ridges formed on a second surface formed on another one of said valve piston and said plunger, said grooves and ridges being alternately arranged along a circumferential direction of the other one of said valve piston and said plunger, said second surface opposing to said first surface,

wherein said ridges hold said seal member and prevent said seal member from pulled off from the first surface formed on said one or said valve piston and said plunger and at the same time said grooves cooperatively define an air passage between said valve piston and said plunger.

2. The pneumatic tool in accordance with claim 1 , wherein said ridges cooperatively define an effective diameter of a guide along which said seal member is guided, and said grooves define an effective area of a relief passage of compression air of a valve piston chamber in which said plunger is accommodated.

3. The pneumatic tool in accordance with claim 1 , wherein said grooves and ridges are arranged alternately and extend in an axial direction of said plunger.

4. A pneumatic tool comprising a circular cylinder, a piston slidably accommodated in said circular cylinder, a driver blade integrally formed with said piston, and a sleeve valve portion for driving said piston when compression air is discharged from a sleeve valve chamber via a trigger valve portion, wherein

said bigger valve portion further comprising:

a plunger shifting in response to a trigger operation by a user;

a valve piston slidably supporting said plunger and shifting in a direction opposed to a shifting direction of said plunger; and

a valve bush slidably supporting said plunger and said valve piston so as to allow slide movements of said plunger and said valve piston;

a seal member provided on a first surface formed on either said valve bush or one of said plunger and said valve piston; and

combined grooves and ridges formed on a second surface formed on another one of said valve bush and said one of said plunger and said valve piston, said grooves and ridges being alternately arranged along a circumferential direction of the other one of said valve bush and said one of said plunger and said valve piston, said second surface opposing to said first surface,

wherein said ridges hold said seal member arid prevent said seal member from being pulled off from the first surface formed on either said valve bush or said one of said plunger and said valve piston and at the same time said grooves cooperatively define an air passage between said first surface and said second surface.

5. The pneumatic tool in accordance with claim 4 , wherein said ridges cooperatively define an effective diameter of a guide along which said seal member is guided, and said grooves define an effective area of a relief passage of compression air of a valve piston chamber 3 . n which said plunger is accommodated.

6. The pneumatic tool in accordance with claim 4 , wherein said grooves and ridges are arranged alternately and extend in an axial direction of said plunger.

7. A pneumatic tool comprising a circular cylinder, a piston slidably accommodated in said circular cylinder, a driver blade integrally formed with said piston, and a sleeve valve portion for driving said piston when compression air is discharged from a sleeve valve chamber via a trigger valve portion, wherein

said trigger valve portion further comprises:

a plunger shifting in response to a trigger operation by a user;

a valve piston slidably supporting said plunger;

a valve bush slidably supporting said plunger and said valve piston;

a seal member provided on a first surface formed on at least one of said plunger, said valve piston, and said valve bush; and

combined grooves and ridges formed on a second surface opposing to said first surface, said second surface being formed on a second one of said plunger, said valve piston and said valve bush, said grooves and ridges being alternately arranged along a circumferential direction of the second one of said plunger, said valve piston and said valve bush;

wherein said ridges hold said seal member and prevent said seal member from being pulled off from the first surface formed on the at least one of said plunger, said valve piston and said valve bush and at the same time said grooves cooperatively define an air passage between said first surface and said second surface.

8. The pneumatic tool in accordance with claim 7 , wherein said ridges cooperatively define an effective diameter of a guide along which said seal member is guided, and said grooves define an effective area of a relief passage of compression air of a valve piston chamber in which said plunger is accommodated.

9. The pneumatic tool in accordance with claim 7 , wherein said grooves and ridges are arranged alternately and extend in an axial direction of said plunger.