Throttle valve device for a pneumatic power tool

A pneumatic power tool comprising a housing, a motor and a smooth-start throttle valve for controlling a pressure of an air supply to the motor, wherein the throttle valve comprises:

• a casing with an inlet passage;
• an outlet passage;
• an annular main valve seat separating the inlet and outlet passages;
• a ball valve element co-operating with said main valve seat in a closed throttle valve condition;
• a manually operable activating rod supported in a transverse guide way in the casing, said activating rod being arranged to displace the ball valve element out of sealing engagement with said main valve seat in an open throttle valve condition;
• a bypass passage extending past the main valve seat, said by-pass passage being formed by a waist portion on the activating rod;
• and
• a secondary valve element carried by the activating rod and arranged to co-operate with a secondary valve seat located on and at the and of the guide way;
• wherein the secondary valve element is arranged to open the bypass passage by being displaced from said secondary valve seat before the activating rod contacts and displaces the ball valve element from the main valve seat upon displacement of the activating rod.