| 摘要 |
The invention relates to a placement head assembly (100) for use in an electrical component placement machine and to a method of placing components on a circuit board. A hollow main shaft (34) has a carriage assembly (124, 126) disposed thereabouts. Rollers (144, 146, 148, 150) on the carriage assembly engage the shaft outer surface (34), providing for axial movement along the shaft. A vacuum support shaft (106) in coaxial alignment within the main shaft telescopes downwards to pickup and retain a component for subsequent alignment in a plane substantially normal to the longitudinal shaft axis. The carriage assembly carries actuator means (152, 154, 156, 158, 136, 160, 162) urging the carriage assembly into axial movement in response to fluid pressure differentials. Tweezer means are pendantly disposed in quadrature from pivot points about the shaft. Jaws at the lower ends of the tweezer means are thereby positioned circumferentially about the component when suspended from the vacuum support. Downward movement of the carriage assembly causes roller surfaces thereon to engage corresponding surfaces of upper ends of the tweezer means, thereby forcing these upper ends radially outwards. Pivoting action of the tweezer means correspondingly forces the jaws radially inwards from four quadrants into contact with the component, thereby aligning it for subsequent board placement. In one embodiment, the actuator means includes a piston-cylinder assembly. Pressure differential across the piston causes downward movement of the carriage assembly. Reverse pressure differential urges the carriage assembly upward. Spring-loaded return of the jaws to the radially outwards position prior to contact with the component is thereby facilitated. |
