Patent ID: 7040679

Claim:
A vacuum suction device comprising a suction head for sucking a workpiece, a negative pressure source and a positive pressure source, a single switching valve for selectively connecting the negative pressure source and the positive pressure source to the suction head, a first passage for connecting the switching valve and the suction head with each other, a second passage for connecting the switching valve and the negative pressure source with each other, a third passage for connecting the switching valve and the positive pressure source with each other, and a throttle device provided in the third passage, wherein the switching valve is a two position valve comprising a first switching position which interrupts the third passage and connects the first passage and the second passage with each other, and a second switching position which interrupts the second passage and connects the first passage and the third passage, and wherein a total volume in the first passage is defined as V 1 , a total volume of a main passage portion from the throttle device in the third passage to the switching valve is defined as V 2 , a negative pressure in the first passage when the workpiece is sucked by the suction head is defined as P 1 , a positive pressure of the main passage portion when the workpiece is sucked is defined as P 2 , and an internal pressure of the first passage and the main passage portion immediately after the switching valve is switched in a state in which the workpiece is sucked by the suction head and the first passage and the third passage are brought into communication with each other is defined as Ps, in the following equation, P 1 ×V 1 +P 2 ×V 2 =Psx ( V 1 +V 2) the pressures P 1 and P 2 , as well as passage volumes V 1 and V 2 are associated with each other such that the Ps is equal to or less than the atmospheric pressure which is necessary for the workpiece to drop by its own weight from the suction head.