JPH0524073B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an excitation current control circuit for a lifting magnet device for attracting and moving slag and the like.

(Prior Art) Lifting magnets used in overhead cranes and the like are now operated by two systems: on-board operation and wireless remote control. When switching between such operating systems, the switching is sometimes done without checking the status of the other system, resulting in accidents where suspended loads fall. Conventional measures to prevent accidents from dropping suspended loads include the following: Depending on the work procedure, switching between on-board operation and wireless operation should not be performed while the load is being lifted.

Take safety measures such as converting to DC, which has a large residual magnetic field (so it will not fall if the power is cut off for a short time), or using a separate power source.

Incorporates a circuit to prevent suspended loads from falling due to incorrect operation (Utility Model Application No. 176186/1986).

(Problem to be solved by the invention) When switching between on-machine operation and wireless operation is not performed while the load is being lifted, etc. to prevent the load from falling, for example, if the material is sucked up using the wireless operation. When switching to on-machine operation during operation, if the on-machine controller is in the release position, the material will fall just by switching the operation. In reality, such accidents have not disappeared. Furthermore, it is uneconomical to separate power sources for each system, and conventional suspended load fall prevention circuits are complex.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a drop prevention circuit with a simple structure that can reliably prevent a suspended load from falling due to switching of the operating system of a lifting magnet having two or more operating systems.

(Means for Solving the Problems) Thus, the gist of the present invention is to provide a circuit for controlling the excitation current of a lifting magnet device using two or more operating systems, including a switch for switching the operating systems, and a switch for switching the operating systems; An operation circuit that commands an excitation current state for each system, and a control circuit that outputs an excitation command when the excitation command is output from at least one of the operation systems, and the control circuit of each operation system, It is equipped with a self-holding circuit that self-holds the excitation command and a reset circuit that resets the excitation command, and when the changeover switch is switched to the relevant operation system, it is activated by the relevant reset command, and when it is switched to another operation system. In this case, the lifting magnet suspended load fall prevention circuit is characterized in that the self-holding circuit of the excitation command is reset by the excitation command.

(Function) The self-holding circuit allows the excitation command to be held in the on-board operating system even if the changeover switch is switched to the remote operating system while the on-board operating system is attracting excitation.

This excitation command can be reset and canceled by:
Limited to the following two cases: When the changeover switch is switched to the relevant on-machine operating system itself and the excitation reset command is output.

When the changeover switch is switched to the remote control system and an excitation command is output by remote control.

This is a case where the excitation current is turned off or released using the on-board control system during operation. Due to normal switch operation based on the operator's intention.

This is a case where the excitation command from the on-board operating system is taken over by the excitation command from the remote operating system.

Note that for excitation and reverse excitation (release), it is preferable to provide a protection circuit that cannot be turned on unless the other is turned off.

(Example) Next, an example of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram showing the basic configuration of a control circuit according to the present invention, and this control circuit includes an on-board operating system having operating switches S ₁ , S ₂ , and S ₃ , and operating switches S ₄ , It has two wireless (remote) control systems with S ₅ and S ₆ . Switching of the operating system is performed by a changeover switch S.

On-board operating system Each symbol A1, B1, C1 in the circle in the circuit diagram is an excitation (attraction) command in the on-board operating system,
These are the off command and the reverse excitation (release) command.

Parallel lines A1, D1, and D2 in the circuit diagram indicate relay contacts, which are turned on when commands A1, D1, and D2 are on, respectively. However, the contacts A1 and B1 whose parallel lines are shaded are commands A1 and B1, respectively.
Turns on when B1 is off.

Wireless operation system A2, B2, and C2 in the circle are excitation, cut, and reverse excitation commands for the wireless operation system, and correspond to A1, B1, and C1 of the on-board operation system, respectively. Similarly, operation switches S ₄ , S ₅ , and S ₆ correspond to S ₁ , S ₂ , and S _{3 ,} respectively. Further, the operation of the relay contacts is the same as in the case of the above-mentioned on-board operating system.

Final command Excitation command A that finally commands the excitation current state
turns on when either command A1 or A2 is on. Reverse excitation command C is also commands C1 and C2.
It turns on when any one of them is on. However, neither A nor B is turned on unless the other command is turned off.

Fig. 2 is a circuit diagram showing the connection state of the lifting magnet to the excitation current power source, and the contacts A and C indicated by parallel lines in the figure are turned on when the final commands A and C are on, respectively. (contact state).

Operation A specific example of the operation of this embodiment will be explained: When a suction operation (regardless of strong excitation or weak excitation) is performed using the operation switch _S4 with the switch S switched to the wireless system, the wireless suction command A2 is held. be done.

When the switch _S5 is turned on and turned off in this state, the suction command A2 is reset and the magnet is de-energized.

When the switches S ₅ and S ₆ are sequentially turned on in this state and a release operation is performed, the attraction command A2 is reset and the magnet is reversely excited.

When switching to on-machine selection using switch S (while material is being sucked), even if the on-machine operation switch is in the OFF or release position, wireless suction command A2 will remain set and the material will not fall. do not.

In this state, if you want to perform the release operation, turn on the on-board operation switch _S1 once to set the on-board suction command A1, reset the wireless suction command A2, and then perform the release operation.

Note that the operation when switching from the on-board selection state to wireless selection is also the same as ~ above.

(Effects of the Invention) As can be seen from the above explanation, if the circuit of the present invention is used, when the operating system is switched during suction of material,
Even if the operation system switch is in the release position after switching, the material will not fall just by switching the operation.

As described above, the present invention can reliably prevent the accident of dropping a suspended load when switching the operating system of a lifting magnet with a simple structure.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the basic configuration of an embodiment of the present invention; and FIG. 2 is a circuit diagram showing the exciting current connection state of the lifting magnet based on the final command.

Claims (1)

[Scope of Claims] 1. A circuit that controls the excitation current of a lifting magnet device using two or more operation systems, comprising: a changeover switch that switches the operation systems; an operation circuit that commands the excitation current state for each operation system; a control circuit that outputs an excitation command when the excitation command is output from at least one of the operating systems; and a self-holding circuit that allows the control circuit of each operating system to self-hold the excitation command; and a reset circuit for resetting the excitation command, when the changeover switch is switched to the relevant operation system, the reset command is used, and when the switch is switched to another operation system, the excitation command is used to activate the self-holding circuit of the excitation command. A lifting magnet suspended load fall prevention circuit characterized by resetting the lifting magnet.