11  EP 3 800 011 A1 12  by tapering the inner peripheral surface of the pipe line 23 ora stepped shape maybe used insteadofthe tapered shape. troduced fromthe upstreamside,and when the airsupply sourcesuch asan aircompressorisconnected,the com- pressed air is supplied to the upstream side at all times. On the downstream side of this flow amount adjustment mechanism, the air outlet 40 to which the duster pipe arrangement42 (the jointpart41)isconnectableisopen. 5 10 [0044] In the presentembodiment,the sealing member 37 formed of an O ring or the like is fixed to the housing side of the tool body 11. Under natural conditions, as shown in FIG. 15, this sealing member 37 abuts on the outer peripheral surface (a sealing surface 38) of the valve member 31 to seal so that no air flows into the intake 33. When the valve member 31 moves in the di- rection that opens the pipe line 23, the sealing state of the sealing member 37 and the sealing surface 38 is re- leased, so that air is supplied from the intake 33 to the inner pipe line 34. The flow amount of the air supplied to the inner pipe line 34 is controlled by the change in the clearance amount at the throttle portion 23a and changein the opening amount ofthe opening portion 35. The airhaving its flow amountcontrolled isreleased from the air outlet 40 and jetted out of the nozzle 17b. In the present embodiment, it is unnecessary to dispose the duster pipe arrangement42 inside the housing since the valve member 31 and the air outlet 40 are disposed in the pushing direction of the operation portion 30 and the air outlet 40 is formed on the side opposite to the oper- ation portion 30. [0040] The pipe line formation portion 20 has a hollow portion forming the pipe line 23, and in the present em- bodiment,partofthehousing ofthe toolbody 11 is made the pipe line formation portion 20. That is, in the housing of the tool body 11, a through hole that passes through in a direction orthogonal to the driving direction of the fastener is formed, and the pipe line 23 is formed of this through hole. This pipe line formation portion 20 is struc- tured, as shown in FIG. 16, so as to take in the com- pressed air into the pipe line 23 from the upstream open- ing portion 21thatisopen toward the upstreamside.This pipe line formation portion 20 is provided with a blocking portion 23i capable of adjusting the opening amount of an opening portion 35 described later. The blocking por- tion 23i has a cylinder inner surface shape facing the outer peripheral surface of the valve member 31. 15 20 25 30 [0041] Thevalve member31 isstructuredso astoslide along with the depression of the operation portion 30. While the valve member 31 is pushed in the protruding direction by the valve memberpushingmember36 under natural conditions, when the operation portion 30 is de- pressed against the pushing force of the valve member pushing member 36, the valve member 31 moves in the direction that opens the pipe line 23. [0045] According tothisstructure,since theflow chan- nel area can be stepwisely adjusted by the flow amount adjustment at two places, even when the pressure dif- ferencebetweenin frontofand behind the throttle portion 23a becomes small by operating the operation portion 30 to a certain extent and the pressure to jet out the air decreases, the decrease in the pressure can be com- pensated by the increase in the flow channel area, so that the relationship between the operation amount of the operation portion 30 and the amount of air jetted out of the nozzle 17b can be made close to a proportional relationship. [0042] This valve member 31 is hollow and provided with aninner pipe line 34 through which aircan pass.On the upstream side of the inner pipe line 34, an intake 33 for taking in the compressed air is provided, and on the downstream side of the inner pipe line 34, the opening portion 35 fordischarging thecompressed airtoward the air outlet 40 is provided. The compressed air supplied from the air supply source flows into the inner pipe line 34 from the intake 33, and passes through the opening portion 35 to flow in a direction toward the air outlet 40. The opening portion 35 is open in a direction orthogonal to the movement direction of the valve member 31, and canfacethe blocking portion 23iofthe pipe line formation portion 20.Specifically, this opening portion 35isprovid- ed, as shown in FIGS. 17A to 17D, continuously with the throttle portion 23a described later, and after the valve member 31 moves and the throttle portion 23a passes the blocking portion 23i,the openingportion 35 faces the blocking portion 23i. 40 35 [0046] That is, according to the present embodiment, as shown in FIGS.17A to17C,since the opening portion 35 is blocked until the operation portion 30 is operated and moves to a predetermined position, the flow amount adjustment is performed only by the throttle portion 23a. At this stage, as shown in FIG. 18A, the flow amount of the airis controlled by the changeintheamountofclear- ance between the throttle portion 23a and the blocking portion 23i. Then, as shown in FIG. 17D, when the op- eration portion 30 is further operated and moves to the predetermined position, part of the opening portion 35 moves to the downstream side of the blocking portion 23i, so that the air flows directly to the downstream side from the opening portion 35. At this stage, the amount adjustment by the throttle portion 23a is not per- formed, and as shown in FIG. 18B, the flow amount of the airis controlled by thechange in the opening amount of the opening portion 35. [0047] According to this structure, the flow amount of the air can be increased as a stretch when the operation portion 30isoperated to a certain extent.Forthisreason, [0043] On the downstream side ofthisopening portion 35, the throttle portion 23a is provided that controls the flow amount of the air in the pipe line 23 by gradually changing the amount of clearance between the pipe line 23 and the valve member 31 when the valve member 31 moves. While the throttle portion 23a is formed by taper- ing the outer peripheral surface of the valve member 31 in the present embodiment, the present invention is not limited thereto; the throttle portion 23a may be formed 55 50 45 7