Rotary valve

A valve comprising:

• a valve body having a body cavity with a fluid flow passageway therethrough defining a fluid flow-path intersecting the body cavity;
• a flow control means movably disposed in the body cavity for selectively closing and opening the fluid flow passageway;
• a valve operator means connected to the flow control means and comprising:
• a single valve operator;
• a stem mounted for movement in reciprocal directions relative to, and independent of, the flow control means, said stem having a stem axis;
• a stem moving means associated with the single valve operator and the stem, said stem moving means for moving the stem in reciprocal directions with respect to the flow control means to cause the stem to move in a sequence of steps that provides axial motion away from the flow control means and then rotary motion in response to movement of the single valve operator in one direction, and rotary motion and then axial motion towards the flow control means in response to movement of the single valve operator in another direction;
• and
• stop means disposed on the flow control means for arresting axial movement of the stem towards the flow control means and thereby transmitting a stem force to the flow control means, such that movement of the single valve operator in said one direction causes the flow control means to be substantially unloaded of axial force from the stem and then the stem rotated, and movement of the single valve operator in said another direction causes the stem to be rotated and then the flow control means loaded with an axial force by the stem so as to provide a better sealing function in a selected valve position than when an axial force by the stem has not been applied to the flow control means.