13  EP 3 800 011 A1 14  even when the pressure difference between in front of and behind the throttle portion 23a becomes small by operating the operation portion 30 toa certain extentand the pressure to jet out the air decreases, the decrease in the pressure can be compensated by the increase in the flow channel area, so that as shown in FIG. 19, the relationship between the operation amount of the oper- ation portion 30 and the amount of air jetted out of the nozzle 17b can be made close to a proportional relation- ship. becomes small by operating the operation portion to a certain extent and the pressure in an accumulator de- creases, the decrease in the pressure can be compen- sated by the increase in the flow channel area, so that the relationship between the operation amountoftheop- eration portion and the amount of air jetted out of the nozzle can be made close to a proportional relationship. 5 10 15 [0052] According to an aspect of the invention, there is provided an air duster structure that is configured to jetcompressedairoutofa nozzle,theairdusterstructure comprising:a flow amountadjustmentmechanismwhich is configured to adjust an amount of air jetted out of the nozzle,wherein the flow amountadjustmentmechanism includes: a pipe line for circulating air; a valve member disposed inside the pipe line and being movable; and a throttle portion configured to gradually change an area ofaflow channelin whichaircirculates,with a movement of the valve member, to control a flow amount of the air in the pipe line, and the throttle portion has a stepped shape where the area of the flow channel is stepwisely changed when the valve member moves. [0048] While in the above-described embodiment, the flow amount of the air in the pipe line 23 is controlled by the change inthe clearance amountatthe throttle portion 23a and the change in the opening amountofthe opening portion 35,the method ofadjustingthe flow channelarea by the flow amountadjustmentattwo places isnotlimited thereto. That is, at least two throttle portions where the flow channel area change amounts with respect to the movement amount of the valve member 31 are different may be provided. For example, a throttle portion where the change in theflow channelareaissmalland a throttle portion where the change islarge maybe combined.Spe- cifically, by providing two or more tapered throttle por- tions as described in the first embodiment and making the angles ofthe tapered surfacesofthe throttleportions different from each other, the flow channel area change amounts with respect to the movement amount of the valvemember31 can be made differentfromeach other. 20 25 30 35 [0053] In the above described structure, the throttle portion has thestepped shapewhere thearea ofthe flow channel is stepwisely changed when the valve member moves.According to the structure,the flow channelarea can be stepwiselyadjusted bythe steppedshape.There- fore,evenwhen thepressure difference betweenin front of and behind the throttle portion becomes small by op- erating the operation portion to a certain extent and the pressure to jet out the airdecreases, the decrease in the pressurecanbe compensated bythe increaseintheflow channel area, so that the relationship between the oper- ation amount of the operation portion and the amount of air jetted out of the nozzle can be made close to a pro- portional relationship. [0049] In the above-described embodiment, the open- ing portion 35 is provided on the valve member 31, and the blocking portion 23i is provided on the pipe line for- mation portion 20 (the pipe line 23). However, the open- ing portion 35 may be providedonthe pipe line formation portion 20 (the pipe line 23), and the blocking portion 23i may be provided on the valve member 31. [0054] By stepwisely adjusting the flow channel area, it is made easy to keep constant the amount of air jetted out of the nozzle. That is, if the release valve or the pipe line is formed in the tapered shape and the amount ofair isadjusted,the operation amountofthe operation portion directly affects the amount of air being jetted out, so that in order to keep constant the amount of air jetted out of the nozzle, it is necessary that the operation amount of the operation portion be also kept constant. For this rea- son,itis difficulttokeep constantthe amount ofairjetted out of the nozzle in a situation where it is difficult for the user to continue applying a constant force to the opera- tion portion (for example, in a situation where the user uses the machine while shaking the nozzle under a con- dition where he/she is holding the machine) . In this re- gard, according to the present invention, since amount of air jetted out of the nozzle can be kept sub- stantially constant even if the operation amount of the operation portion changes in some degree, the amount ofairjetted outofthe nozzle can be keptconstantwithout the user continuing to apply a constant force to the op- eration portion. [0050] According to an aspect of the invention, there is provided an air duster structure that is configured to jetcompressed airoutofa nozzle,the airdusterstructure comprising:a flow amountadjustmentmechanismwhich is configured to adjust an amount of air jetted out of the nozzle, wherein the flow amountadjustmentmechanism includes: a pipe line for circulating air; a valve member disposed inside the pipe line and being movable; and a throttle portion configured to gradually change an area ofa flow channelin which aircirculates,with a movement of the valve member, to control a flow amount of the air in the pipe line, and the throttle portion is structured so as to increase the area of the flow channel at an accel- erated rate when the valve member moves in a direction that opens the pipe line. 40 45 50 55 [0051] In the above described structure, the throttle portion isstructuredsoas toincrease the area ofthe flow channel at an accelerated rate when the valve member movesin the direction thatopens thepipe line.According to the structure, as the operation amount increases, the flow channel area of the throttle portion increases at an accelerated rate.Therefore,evenwhen thepressure dif- ference between infrontofandbehind the throttle portion [0055] According to an aspect of the invention, there 8