Valves are used for many industrial applications like for closing or modifying the passage through a pipe, preventing the process flow from reversing, for corrosion resistance, for chemical handling and for many more such applications. They are offered in various price ranges in the market, which makes it comfortable for every pocket.A pinch valve is a full bore or fully ported type of control valve which presents no obstruction to flow passage. There are a few types of pinch valves based upon application. Pinch valves used for fluids usually employ a device that directly contacts process tubing. Forcing the tubing together will create a seal that is equivalent to the tubing's permeability. Major components of a pinch valve consist of body and a sleeve. The sleeve will contain the flow media and isolate it from the environment hence reducing contamination to the environment. Generally used for slurries or processes with entrained solids, because the flexible sleeve allows the valve to close drop tight around solids-solids that would typically be trapped by the seat or stuck in crevices in globe, diaphragm, butterfly, gate, or ball valves. The sleeve material can be selected upon the corrosiveness and abrasiveness of the flow media, a suitable synthetic polymer can be chosen. A pinch valve may be the best type of valve for flow control application if the operation temperature is within the limit of the polymer. This invention provides a pinch valve having a pinch region defined by a pair of rotating pinch elements. These pinch elements define a variable profile that substantially surrounds the entire circumference of a tube in the pinch region and that thereby ensures that the tube is always returned to the desired opening size at all valve adjustment settings in a range from fully open to fully closed.
More particularly, the pinch elements are provided with a pinch region that defines a surface geometry that includes a continuously variable-length (ramping) linear segment, disposed at a continuously variable depth (ramping from full open to fully pinched), that pinches the walls into a pair of opposed parallel lines throughout the majority of their rotational movement/adjustment range. The pinch elements also include upper and lower variably sized fillets (typically curved) on each side of the linear segment that capture the curved top and bottom of the tube, adjoining the pinched walls, so as to force the top and bottom back into a desired shape despite the presence of any permanent deformation of the walls. Overall, the pinching region is adapted to conform to the prevailing outline of the tube at the pinch point throughout the range of pinch settings. In an illustrative embodiment, the pinch elements counter-rotate, so that parallelism between opposing pinched walls is enhanced.
