1.  Field of the Invention
This invention relates to a louvered grille unit which is generally mounted over a fluid or air outlet to adjustably direct fluid or air.  Also, it relates to a method of manufacturing the grille unit. 
2.  Description of the Prior Art
An automotive vehicle has air outlets in its instrument panel to ventilate or air-condition the passenger compartment.  The air outlets are usually equipped with grille units for directing the air.  Some grille units have pivotal parallel vanes or louvers to allow the direction of discharged air flow to be changed manually. 
Japanese Patent Publication No.  54-26266 (Filing No.  51-92432) discloses such an adjustable louvered grille unit and a method of its manufacture.  The grille unit has a frame and louvers or vanes pivotally mounted to the frame.  The vanes are made by injection molding.  After a mold for the vanes is assembled with the previously-formed frame positioned within the cavity of the mold, synthetic resin is injected into the mold.  The frame has holes which are to allow pivotal engagement between the frame and the vanes in the finished product.  A fraction of the synthetic resin fills the holes during molding to form vane pivots which are rotatably received in the holes.  The holes have a stepped profile to provide the ends of the vane pivots with bosses or greater-diameter portions.  The bosses limit or prevent movement of the vanes along the axes of the pivots.  The bosses are pressed against the frame due to mold shrinkage, resulting in frictional contact between the frame and the vanes.  Thus, the vanes remain in their respective angular positions as long as they receive no pivotal force. 
However, in such a grille unit, pressure between the frame and the bosses tends to be excessively great, preventing smooth rotation of the vanes and immoderately deforming the frame.  What is worse, each of the frictional contacts between the frame and the vanes is liable to be angularly uneven, so that irregularly varying forces are necessary to pivot the vanes.