[Adger Smith]

Ray,
We are actually using the term pinch valve incorrectly in this throttle stop application. It is usually a needle valve used to control the air flow.
Needle Valves

The needle valve is used specifically for accurately controlling the flow of fluids at low flows. The valve is basically a globe valve without the disc. It is generally used provided in small sizes of up to 20mm bore..


This is a good example of a pinch valve:
Pinch Valves

The pinch valve is a theoretically ideal solution for fluid on-off duties. The valve is simple a length of pipe made from an elastomeric material with a mechanical system for squeezing the tube closed when a shut off is required. The valve is a true full bore valve - there are no mechanical parts in contact with the fluid- The operation of the valve is ideally simple- The valve can be easily engineered as a tight-shut off valve..

The valve is often supplied with the pinch tube contained within a outer pipe between the end flanges. This option provides a method of monitoring for tube leaks and provides a degree of secondary containment

The valve has similar limitations to the diaphragm valve. The diaphragm valve is really a variation on the pinch valve principles.. Pinch valves are supplied is for diameters 25 mm - 1000 mm, temperatures -50 C - +160 C, and pressures 0 - 100 bar.

Sorry can't get the pictures to copy.