Abstract A method for transporting loads safely utilizing a permanent magnet type lifting magnet having a permanent magnet provided in its magnetic circuit and an exciting winding for controlling the magnetic flux developed in said magnetic circuit and adaptable to be operated in an attraction mode in which a load is to be attracted, a lifting mode in which the attracted load is lifted and a transportation mode in which the load is transported, said method comprises the steps of applying an exciting current of a predetermined value to the exciting winding for producing an attractive magnetic force during the attraction mode, reducing the exciting current to a value of zero or less thereby making the magnetic flux less than the residual magnetic flux due to its remanence during the lifting mode and increasing the exciting current to larger than zero during at least the initial period of the operations in the transportation mode, thereby providing the lifting magnet with magnetic flux larger than the residual magnetic flux corresponding to the remanence under the condition in the lifting mode.
A method of transporting loads by utilizing a permanent magnet type lifting magnet having a permanent magnet provided in its magnetic circuit and an exciting winding for controlling the magnetic flux produced in said magnetic circuit, said method comprising the steps of: a. applying an exciting current of a first value to said exciting winding during the operations in an attraction mode in which a load to be transported is attracted to the lifting magnet, b. reducing the exciting current to a second value of zero or less thereby making the magnetic flux produced by the circuit less than the residual magnetic flux due to its remanence during the operations in a lifting mode in which the load is lifted, and c. increasing the exciting current to a third value larger than zero thereby making the magnetic flux produced by the circuit larger than the residual magnetic flux corresponding to the remanence under the condition in the lifting mode during the operations in a transportation mode in which the load is transported.
Claim 2
Independent Claim
172 words
A method of transporting loads by utilizing a permanent magnet type lifting magnet having a permanent magnet provided in its magnetic circuit and an exciting winding for controlling the magnetic flux produced in said magnetic circuit, said method comprising the steps of: a. applying an exciting current of a first value to said exciting winding during the operations in an attraction mode in which a load to be transported is attracted to the lifting magnet, b. reducing the exciting current to a second value of zero or less thereby making the magnetic flux produced by the circuit less than the residual magnetic flux due to its remanence during the operations in a lifting mode in which the load is lifted, and c. increasing the exciting current to a third value larger than zero thereby making the magnetic flux produced by the circuit larger than the residual magnetic flux corresponding to the remanence under the condition in the lifting mode during the operations in a transportation mode in which the load is transported.
Claim 3
Dependent Claim
49 words
A method according to claim 1, wherein the third value of the exciting current is held larger than zero thereby providing the lifting magnet with magnetic flux larger than the value corresponding to the remanence under the condition in the lifting mode during the operations in the transportation mode.
Claim 4
Dependent Claim
24 words
A method according to claim 2, wherein the exciting current during the operations in the transportation mode is not larger than said first value.
Claim 5
Dependent Claim
48 words
A method according to claim 1, wherein said exciting current during the operations in the transportation mode is once increased to substantially the same value as said first value and then reduced to and held at a fourth value less than said first value and larger than zero.
Claim 6
Dependent Claim
20 words
A method according to claim 1, wherein said third value of the exciting current is larger than said first value.