| 摘要 |
A speed control device for limiting the idle and operating speed of a pneumatic power tool driven by an air turbine (20) and comprising an inlet passage (16) for supplying pressure air at a pressure (P1), one or more nozzles (25) for directing supplied motive pressure air onto the turbine wheel (22) of the air turbine (20), and a speed governor (21) with a movable valve element (43) biased by a turbine speed responsive control pressure (P3) and arranged to control the flow of supplied pressure air from the pressure air inlet passage (16) to the nozzles (25), wherein a pressure regulator (60) controlled by the pressure air supply pressure (P1) is arranged to adjust the control pressure (P3) by adjusting the size of a bleed passage (66) communicating with the atmosphere in response to the actual level of the pressure air supply pressure (P1) such that a decreasing pressure air supply pressure (P1) results in an decreased area of the bleed passage (66) and a following increased control pressure which results in an increased pressure air flow to the turbine nozzles (25) and a compensation for occurring variations in the pressure air supply pressure (P1). |
