Lifting magnet and steel plate lifting apparatus, and steel plate conveying method
A lifting magnet including a plurality of electromagnetic coils that are disposed in a nesting arrangement and capable of being independently ON/OFF-controlled and voltage-controlled. By using the plurality of electromagnetic coils in a selective or appropriately combined manner, the lifting magnet secures a sufficient magnetic flux penetration depth during conveyance of steel plates, and can easily and highly precisely control the magnetic flux penetration depth in accordance with the number of steel plates to be lifted.
1 . A lifting magnet comprising:
a plurality of electromagnetic coils disposed in a nested arrangement and configured to be independently ON/OFF-controlled and voltage-controlled;
an inner pole disposed inside an innermost coil of the plurality of electromagnetic coils;
an intermediate pole interposed between adjacent coils of the plurality of electromagnetic coils;
an outer pole disposed outside an outermost coil of the plurality of electromagnetic coils; and
a yoke disposed in contact with upper ends of the inner pole, the intermediate pole, and the outer pole; wherein a maximum amount of magnetic flux of the innermost coil is smaller than a maximum amount of magnetic flux of all other electromagnetic coils.
2 . The lifting magnet according to claim 1 , further comprising a magnetic flux sensor configured to measure a magnetic flux density directly under magnetic poles of the lifting magnet.
3 . The lifting magnet according to claim 2 , wherein the magnetic flux sensor is disposed at a lower end of an inner pole disposed inside an innermost coil of the plurality of electromagnetic coils.
4 . A steel plate lifting apparatus comprising:
the lifting magnet according to claim 3 ; and
a control device programmed to execute a step of controlling an operation of the plurality of electromagnetic coils using a magnetic flux density measured by the magnetic flux sensor.
5 . A steel plate lifting apparatus comprising:
the lifting magnet according to claim 3 ; and
a control device programmed to execute a step of controlling an operation of the plurality of electromagnetic coils using a magnetic flux density measured by the magnetic flux sensor.
6 . The steel plate lifting apparatus according to claim 5 , wherein the control device performs the control such that a voltage corresponding to a set number of steel plates to be lifted is applied to the plurality of electromagnetic coils, and the control device is further programmed to execute the steps of:
calculating, from the magnetic flux density measured by the magnetic flux sensor, a magnetic flux penetration depth for the steel plates to be lifted;
determining, from the calculated magnetic flux penetration depth, whether the number of steel plates to be lifted matches the set number; and
controlling the voltage applied to the plurality of electromagnetic coils on a basis of the determination.
7 . The steel plate lifting apparatus according to claim 6 , wherein the control device controls a voltage applied to an innermost coil of the plurality of electromagnetic coils to control the number of steel plates to be lifted.
8 . The steel plate lifting apparatus according to claim 5 , wherein the control device performs the control such that some of the electromagnetic coils are excited for lifting steel plates, and such that at least one of all other electromagnetic coils is excited for conveying the lifted steel plates.
9 . A steel plate conveying method performed via the steel plate lifting apparatus according to claim 5 , the steel plate conveying method comprising:
lifting steel plates to be conveyed by exciting some of the electromagnetic coils; and
conveying, after the lifting, the lifted steel plates by exciting at least one of all other electromagnetic coils.
10 . The steel plate conveying method according to claim 9 , wherein the steel plates are lifted by exciting an innermost coil of the plurality of electromagnetic coils; and
after the lifting, the lifted steel plates are conveyed by exciting all other electromagnetic coils.