Bleeder valve assembly

A valve assembly comprising a valve seat, a lid structure including a valve lid which can be fitted in sealing relation on the valve seat, a lever arm, said lid structure being secured towards one end on said arm, said arm being mounted to rotate on a rotatable shaft longitudinally remote from the lid structure, an over-center spring device having an over-center position and being arranged to apply a force to the shaft to rotate the shaft, and drive means arranged to rotate the shaft;

• the arrangement of said valve assembly being such that, with the valve lid fitted on the seat, the spring device urges the shaft in a direction to seal the lid on the seat and, when the shaft is rotated in a direction to displace the lid from the seat, the rotation of the shaft is opposed by said spring device until said over-center position is exceeded whereupon the spring device assists in the rotation of the shaft;
• and in which the lid structure is secured to the arm by first pivot means and is further secured to an elongate link by second pivot means at a point spaced from the first pivot means, said link being mounted to rotate about a fixed pivot axis spaced from the shaft so that during displacement the lid structure is raised essentially upwardly from the valve seat and upon continued rotation of the lever arm the lid structure is then pivoted away from the valve seat.