Patent attributes
A vertical injection molding machine designed to move up/down a large weight by a toggle link mechanism so as to perform mold opening/closing. In a foreign matter detection region where a mold opening/closing servo-motor is subjected to speed feedback control during a mold closing process, a measured torque value of the mold opening/closing servo-motor is compared with a standard torque characteristic curve with no foreign matter between dies. Between a start position of the foreign matter detection region and a position of the foreign matter detection region in which a torque value is zero in the standard torque characteristic curve, it is concluded that there is a foreign matter between the dies when the measured torque is lower than the standard torque characteristic curve by a predetermined value or more. Between the position of the foreign matter detection region in which a torque value is zero in the standard torque characteristic curve and an end position of the foreign matter detection region, it is concluded that there is a foreign matter between the dies when the measured torque is higher than the standard torque characteristic curve by a predetermined value or more. The foreign matter between the dies can be detected surely without provision of any weight compensating mechanism.
