US961342A - Lifting-magnet controller. - Google Patents

Description

A. G. EASTWOOD.

LIPTING MAGNET CONTROLLER.

APPLICATION rmzn um aa, 1909.

961,342. Patented June14,1910= wu-rncssti: mvlzn-roll ARTHUR, C. EASTWOOD, 0F CLEVELAND, OHIO.

LIFTING-MAGNET CONTROLLER.

Specification 01' Letters IPatent.

Application filed January 28, 1909. Serial No. 474,731.

Patented June 14, 1910.

To "all whom it may concern:

Be it known that I, ARTHUR O. EASTWOOD, a citizen of. the United States of America, residing at Cleveland, in the county of Cuyahogal'and State of Ohio, have invented or discovered new and useful Im rovements in Lifting-Magnet Controllers, 0 which the following is a specification.

My invention relates to a controller for controlling the action of alifting magnet.

The chief object of my invention is to secure a more rapid release of the load lifted by the magnet thus increasing the handlinig capacity of a given crane and. magnet and also reducing the percentage of material s illed or misplaced in the process of han- My invention also provides means for o ening the circuit of a lifting magnet, w ich naturally is of a highly inductive nature, reliably, quietly and without excessive insulation stresses.

The use of lifting magnets for handling pig iron, scrap and similar miscellaneous matter necessitates a magnet winding of a large number of ampere turns and also a magnet frame of heavy cross section. Consequently, the circuit including the magnetizing winding becomes high y inductive in nature with the result that when the circuit of the magnet is opened by any of the ordinary switches or circuit controlling devices, a persistent arc of a very flaring or expansive nature is set up, the energy stored in the magnet being discharged through the arc. This arcon account of the inductive characterv of the circuit emits a large volume of light and usually also a considerable sound both of which are likely to prove disconcerting to the operator. Further the persisting character of the are prevents rapid de'energization of the magnet so that all or a ortionof the load lifted thereby has a ten ency to ban on for several seconds after the control or has been operated to release the load. This last point is very objectionable in cases where a material such as pig iron and scrap is being from eighteen to twenty-four inchesin,

consequently material must vbe quite ile accurately deposited by the magnet to avoid excessive spilling. When material is handled by means of a crane and lifting magnet the magnet is usually suspended from hoisting cables or chains of 'from thirty to fifty feet in length. If the motion of the crane is suddenly checked the magnet with its load has a tendency to swing like a pendulum and if uncertainty exists in the release of the load when the magnet controller is operated to denergize the magnet, the magnet is likely to swing past the point where 1t is desired to deposit the load thus causin spilling and scattering of the material Either this will occur or the operator must wait until the load has substantially come to rest before operating his controller to release the load, which, of course, necessitates a loss of time and a reduction in the capacity of the plant. This objectionable condition becomes further ag ravated where the material to be handled wi I retain a considerable percentage of the induced magnetism and the material is of such form as to completely bridge the poles of the magnet this causing the material to more tenaciously cling to the poles of the magnet after the circuit of the magnetizing winding has been opened. My invention ossesses particular advantage when applied to magnets handling material of such a character.

In controlling devices at present commonly used with lifting magnets, when it is desired to release the load, the circuit of the magnet winding is opened at the contacts of a magnetically operated switch under the influence of a powerful magnetic blow-out, and, at the instant of disconnecting the magnet winding from the line the windin is connected in a local or discharge circuit.

In a test I found that a lifting magnet of annular type, capable of lifting elghteen hundred pounds of pig iron per lift, when equipped with this commonly'used control device would hold a load consisting of a plate g of an inch in thickness for nine seconds after the switch was operated to denergize the magnet. With my improved control system identically the same magnet with the same excitation released the same load'in 1 76/100 seconds after the switch was operated to deenergize the magnet. The savin in time and the increased s eed of handhng which may be secured by t e use of my system is evident.

In carryin out my invention, I provide a magnetical y operated switch or switches for connecting the winding of the magnet to the supply circuit, and a master switch for energizing the operating solenoid or solen oids of these switches. I also provide the master controller with contacts by means of which, when it is desired to denergize the magnet and promptly release the load, the magnetizing winding may be connected through a resistance to the line, the ends of the winding being trans osed such that a limited current will flow t rough the magnet winding in the reverse direction.

I find that in the case of a lifting magnet requiring 45 amperes at 220 volts for full excitation, a reverse current of two amperes is sufficient to cause the desired promptness in releasing the load and at the same time this small current is not sufficient to cause the load to cling to the magnet. It is natural to suppose that this more sudden deenergization of the ma net would cause more severe arcing and higher insulation strains than the ordinary forms of magnet controllers which permit the magnet to release its load more slowly. I have discovered, however, that this is not the case. By means of my invention the circuit of the magnet is opened with the occurrence of a smaller and quieter arc and no appreciable disturbance of line voltage occurs.

To describe more fully the operation of my invention reference will be had to the accompanying drawing, which is a diagram of the electrical connections of my invention.

In this drawing the magnet is represented by M, the magnetic switch by D, and the controller by C. The magnetic switch D has an operating solenoid d which simultaneously operates the two contact arms (Z and (Z to make contact with the fixed contacts a? and d (Z and cl represent blow-out coils provided to extinguish the are formed when the said contacts open.

(Z is an auxiliary contact which opens when the solenoid operates to close the main contacts d and (Z In the controller C, the controller arm 0 carries the brush 0* which makes contact with the fixed contacts 0, 0 and 0 when moved to the several operating positions.

When it is intended to energize the magnet for lifting a load, the controller arm 0 1s moved to the position marked Lift, at which time the brush at makes connection with the contacts 0 and 0 A circuit is now established from the positive through the wire 1, the operating solenoid d, the wire 4, the contact 0, the brush 0*, the contact a, and the wire 5 to the negative. This energizes the solenoid d of the magnetic switch D, closing the main contacts 03 d and (1 d and o enin the auxiliary contact d. Current t en ows from the positive throu h the fixed contact d, the movable contact the wire 6, the lifting magnet winding m in the direction of the solid arrow, the wire 7, the movable contact d, and the fixed contact d to the negative. This fully energizes the ma net. If 1t is now desired to drop the load quickly, the controller arm 0 is moved to the position marked Drop so that the brush a connects the contacts 0 and c. As soon as the brush 0 leaves the contact 0', the solenoid d of the magnetic switch is deenergized and the circuit to the ma et- M is interrupted. As soon as the brus a connects the contacts 0 and c a circuit is established from the positive through the auxiliary contactd", the resistance 1' the wire 7 the magnet windin m in the direction 0 the dotted arrow, t e wire 8, the resistance W, the wire 9, the contact 0 the brush 0, the contact 0 and the wire 5 to the negative. This connection allows current to flow through'the magnet windin m in the opposite direction to that while iftin the current being limited to a small va ue by the resistances 'r and a. After the load carried by the magnet has dropped, the controller arm C may be placedin the oil-position to prevent a waste of current which would flow throu h the magnet if the controller arm were Ieft in the drop osition. When it is again necessary to pic up the load the arm 0 is again moved to the position lift.

I claim- 1. In a controller for lifting magnets, the combination of a magneticall closed switch for connecting the windingof the magnet to the supply mains, a master switch, said master switch having contacts for energizin the winding of sald ma etically close switch, and contacts for c osing the circuit of the winding of said magnet to give a reverse direction of current flow through said winding.

2. In a controller for lifting magnets, the combination of a magneticall closed switch for connecting the wlnding o the magnet to the supply mains, a master switch, said master switch having contacts for energizin the winding of said magnetically close switch, contacts for closing the circuit of the winding of said ma net to give a reverse direction of current ow through said winding, and means for limiting the current when flowing in the said reverse direction.

3. In a controller for lifting magnets, the combination of a magnetically closed switch for connecting the winding of the magnet te. the supply mains, a master switch, said master switch having contacts for energiz' the winding of said ma netically close switch, and contacts for c osing the circuit of the winding of said magnet to give a reverse direction of current flow through said winding, there being a space or oil'- position between said first and second mentioned contacts of the master controller.

4. In a controller for lifting magnets, the combination of a m'agneticall closed switch for connecting the winding 0 the magnet to the supply mains, a master switch, said 'master switch havin contacts for energizing the winding of sald magnetically closed switch, contacts for closing the circuit of the winding of said ma netto give a reverse direction of current ow through said winding, there being a space or off-position between said first and second mentioned contacts of the master controller, and means for limiting the flow of current when flowing in the said reverse direction.

5. In a controller for lifting magnets, a magnetically closed switch having main contacts for connecting the winding of the magnet to the supply mains when it is desired to energize the magnet, an auxiliary switch actuated by said magnetically closed switch said auxiliary switch being open when said magnetically closed switch is closed and closed when said magnetically closed switch is open, said auxiliary switch when closed being adapted to connect one end of the winding of the magnet to the supply main opposite to that to which the same end of the winding was connected by the magnetically closed switch, a resistance, and a master controller having in one position contacts"

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