Apparatus for taking out molded product

An apparatus for taking out a molded product, comprising:

• an attachment including a suctioning portion operable to suction a molded product in a die of a molding machine;
• a moving mechanism operable to move the attachment according to an operation sequence determined in advance;
• a moving mechanism control portion configured to control the moving mechanism;
• a negative pressure generating circuit including an air flow path provided between the suctioning portion and a vacuum generating device to generate a negative pressure in a space formed between the suctioning portion and the molded product, and a pressure valve and a pressure detector, both of which are disposed in the air flow path, the negative pressure generating circuit having variation characteristics such that the negative pressure is reduced to an inflection point after the pressure valve is opened and then is started increasing;
• and
• a negative pressure control portion configured to control the negative pressure by controlling the vacuum generating device or the pressure valve, wherein:
• the negative pressure control portion is configured to repeatedly perform on-off control in which a suctioning operation is started by opening the pressure valve when a suctioning start instruction is received, the suctioning operation is stopped by closing the pressure valve when the negative pressure of air flowing through the air flow path reaches a stable value or an upper limit set value, and thereafter the suctioning operation is resumed by opening the pressure valve on a basis of a user-set lower limit value that is lower than the stable value or the upper limit set value;
• the negative pressure control portion includes a determining portion configured to determine a pressure valve resumption time period that is used to resume the suctioning operation such that the inflection point does not become lower than the user-set lower limit value;
• and
• the negative pressure control portion repeatedly performs an off operation to keep the pressure valve closed until the pressure valve resumption time period elapses after the suctioning operation is stopped and an on operation to open the pressure valve and keep the pressure valve open until the negative pressure reaches the stable value or the upper limit set value in the on-off control;
• and wherein
• the determining portion includes:
• a detecting portion for detecting a negative pressure variation tilt configured to detect a tilt of variations in the negative pressure immediately after the negative pressure starts reducing;
• a first computing portion configured to compute an expected time period since the negative pressure starts reducing until the negative pressure is expected to exceed the inflection point on a basis of a value of the negative pressure at a time when the negative pressure starts reducing, the user-set lower limit value, and the tilt;
• and
• a second computing portion configured to determine the pressure valve resumption time period on a basis of the expected time period.