The CAIDEX valve

 

In traditional compact rotary valves, the sound-path through the valve often involves sharp changes in flow direction and wide variation in the shape and size of the cross-sectional area.  In some designs, the sound-path cross section is ‘squeezed’ near the middle of its transit through the rotor, causing acoustic resistance.  In other designs, the area inside the rotor may be larger and distorted, forming an oversized ‘chamber,’ causing unwanted acoustic reflections that may result in ‘wolf tones.’   

 

The main design objectives of the CAIDEX valve are to (i) eliminate sharp changes in flow direction and cross-sectional area shape and (ii) maintain constant cross-sectional area magnitude along the sound-path—by using internal ducts of variable elliptic cross section: since the area of an ellipse is proportional to the product of the minor and major axes, any contraction of the minor axis as the sound-path is ‘squeezed’ through the compact casing is exactly compensated for by a calculated proportional expansion of the major axis.  The CAIDEX design also uses lipped tubes that provide natural venting, eliminating any pressure buildup-and-release (‘popping’) that would otherwise occur in an intact-duct design during transition between the two operational orientations of the rotor.  Apart from the duct walls and lips and the bearing components, no additional metal mass (‘dead weight’) is involved in the rotor construction, thereby guaranteeing low rotational inertia and very fast action.  This results in a rotor of considerable geometric complexity, as seen on the front cover and on pages 14 and 18, below.  The name ‘CAIDEX’ for the valve is (a slight contraction of) an acronym for: Constant Area Internal Ducts of Elliptic Cross Section.

If you would like the booklet of comparison of standard rotary and CAIDEX valves please email to: mail@willson.ch