| 摘要 |
A cam is rapidly rotated against the actuating stem of a flapper valve to quickly open the valve. The cam is formed on a ratchet wheel which is mounted for limited rotary motion around a rotor. The rotor and attached ratchet wheel are driven slowly forward by a cam shaft until the ratchet wheel is locked by an engaging pawl. The rotor continues to rotate, winding a bias spring connecting the ratchet wheel and rotor. The pawl is disengaged by an escapement cam extending from the rotor and the bias spring unwinds, snapping the ratchet wheel and cam forward to actuate the valve. The valve is held open until the cam is rotated clear of the actuating stem.
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