| 摘要 |
The butterfly valve includes a valve housing (1) with a bore defining a flow passage (2) and a closure disc (3) rotatably mounted around a transverse shaft so as to be moved between a closed position and a full open position. The peripheral surface of the closure disc and the associated valve housing seat surface are both frusto-conical surfaces defined by two circular cones. The closure disc shaft axis is offset.
<??>For a given value of the cone angle 2 of that circular cone defining the valve housing seat surface and a given position C of the closure disc shaft axis in an orthogonal system @@, @ , @ wherein one of the axis is the said cone axis, there is defined a valve butterfly seal plane where the closure disc seals engages the valve housing seat, a couple of points of said seal plane, for which points the minimum clearance angle is maximum, projecting in a point Q located in the plane ( @@, @) of said orthogonal system, the coordinates of those points and the clearance being respectively given by the following approximated relations:
XQ = sin phi cos phi (1 - c<2>)
ZQ = c[(1 - sin<2> phi (1 - c<2>)]
<MATH>
c being the distance from the projection of the closure disc shaft axis to the centre 0 of the orthogonal system, the inclination 0 of the closure disc with respect to the bore axis being given by the complement relation of the blocking angle > theta > pi /4
<??>The compression value epsilon at the fluid-tight surfaces is:
<MATH>
<??>The seal surface is generated by straight lines forming a given angle beta with the generatrix of the first cone at any point of the ellipse E plane in the plane defined by the generatrix and the centre of the ellipse. |
