US3653706A

US3653706A - Lifting magnet for handling cargos

Info

Publication number: US3653706A
Application number: US54786A
Authority: US
Inventors: Shinichi Kashiwagi; Morio Amano; Koichi Nakasawa
Original assignee: Nishishiba Electric Co Ltd
Current assignee: Nishishiba Electric Co Ltd
Priority date: 1970-07-14
Filing date: 1970-07-14
Publication date: 1972-04-04
Anticipated expiration: 1989-04-04

Abstract

A lifting magnet for handling cargoes which includes an elongated pole piece rotatably attached to a framework suspended from a suspension device such as the hook of a cargo crane. The elongated pole piece is rotatably mounted on the framework for being rotated in a plane relative thereto. Thus, when the elongated pole piece is positioned on a plurality of elongated cargos such as I-beams with the longitudinal axis of the pole piece crossing the longitudinal axes of the I-beams, it is possible to lift a plurality of I-beams at the same time. On the other hand, when the elongated pole piece is rotated and positioned on only one I-beam with the longitudinal axes thereof being aligned, it is possible to lift only the selected I-beam.

Description

United States Patent Kashiwagi et al.

Apr. 4, 1972 [54] LIFTING MAGNET FOR HANDLING CARGOS Primary Examiner-Evon C. Blunk Assistant ExaminerJ. Kenneth Silverman [72] Inventors: Shlnlchl Kashlwagi, Takasago; Mono Anomey oblom Fisher & Spivak Amano; Koichi Nakasawa, both of Hlmejl, all of Japan 57 ABSTRACT [73] Assign: Nishishiba Electric -s Himeji A lifting magnet for handling cargoes which includes an elon- JaPan gated pole piece rotatably attached to a framework suspended [22] Filed: July 14, 1970 from a suspension device such as the hook of a cargo crane. The elongated pole piece is rotatably mounted on the PP 54,786 framework for being rotated in a plane relative thereto. Thus, when the elongated pole piece is positioned on a plurality of [52] U S Cl 294/65 5 elongated cargos such as i-beams with the longitudinal axis of [51] 1". .Cl the p piece Crossing the longitudinal axes of the beams it is possible to lift a plurality of l-beams at the same time. On [58] Field of Search ..294/65.5 the other hand, when the elongated p piece is rotated and positioned on only one l-beam with the longitudinal axes [56] References cued thereof being aligned, it is possible to lift only the selected 1- UNITED STATES PATENTS beam- 3,487,964 1/1970 Riley ..294/65.5 7 Claims, 11 Drawing Figures l3; T. l

PATENTEU 4 I9 2 SHEET 1 BF 4 mvrzn'rons SHINICHI KASHIWAGI MORIO AMANO KOICHI NAKASAWA 06m, Fir/M a! 9mm ATTORN EYS PATENTEDAPR 4 I972 SHEET 0F 4 FIG. 10

LIFTING MAGNET FOR HANDLING CARGOS BACKGROUND OF THE INVENTION The present invention relates generally to magnetic lifting devices, and more particularly to an electromagnetic lifting device for handling cargos, and similar loads which are made of magnetic materials.

In the past, many types of magnetic lifting devices have been provided for handling cargoes and similar loads, the best known of which commonly suspend the lifting magnet from the hook, or load-engaging member, of a crane. These devices have had to be relied upon for the handling of various cargos in the field and although they have generally been successfully employed, they have not always proven to be entirely satisfactory in certain operations. One of these operations involves the handling of elongated cargos such as I-beams, rails for railways, ingots and the like.

It is sometimes necessary to load a truck with many elongated cargos of the aforedescribed character at the same time.

Whenever the truck has been substantially fully loaded, however, such that the loading ability of the truck will permit only one or two additional elongated cargos to be loaded thereon,

for example, or that the removal of only one or two of these cargos is required, the magnet must be able to selectively lift the aforesaid only one or two cargos therefrom.

In the magnetic lifting devices heretofore available, a circular surface or circular pole face is generally provided for magnetically attracting the cargos. It can be understood that such magnets can be employed to lift many cargos of the character described simultaneously, but they cannot selectively lift a defined one or two of such cargos from among the others. Therefore, when it is required to lift one or two selected cargos from among the others, it has been necessary to prepare other types of magnets having substantially rectangular configurations, or such other shape which is specifically adapted for the elongated cargos to be selectively lifted.

Such changing of the magnets for selectively lifting cargos, however, is not readily accomplished, of course, unless magnets having configurations different from each other have been previously readied for use. It is therefore not only expensive to make such preparations of the various types of magnets, but also it is inconvenientbecause the changing of the magnets in presently available lifting devices is manually performed and is considered to be a difficult operation.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a magnetic lifting device for use in various cargo operations which does not require changing of the lifting magnet to suit the particular cargo in order to selectively lift only one or two of the cargos from among a larger number thereof.

Another object of the present'invention is to provide a magnetic lifting device for handling cargos in which the magnet includes an elongated pole piece rotatably attached toa lower surface of a framework that is suspended from the book of a cargo crane.

Still another object of this invention is to provide a magnetic lifting device for selectively handling cargos in which the angular disposition of an elongated pole piece relative to a lower surface of a framework suspended from the hook of a cargo crane can be automatically or manually varied by a suitable drive.

A still further object of this invention is to provide a magnetic lifting device for handling cargos in which an elongated pole piece is rotatably attached to a lower surface of a framework and can be rotated by either an electric control signal from the control station of a cargo crane or a similar signal from a switch box suspended from the lifting magnetic device.

Briefly, in accordance with the teachings of the present invention, there is provided a framework which is adapted to be suspended from a suspension device of a cargo crane. At least one electromagnetic pole member is mounted on the lower surface of the framework such that the pole member includes an elongated effective pole face to which cargos are magnetically attracted and the pole member can be rotated in a plane relative to the lower surface of the framework. A drive mechanism on the framework is effective for rotating the pole member within a desired angle in the predetermined plane relative to the framework.

BRIEF DESCRIPTION OF DRAWINGS Various other objects, as well as additional features and advantages of the present invention will be more fully appreciated as the same becomes better understood from the following detailed description when considered in conjunction with the accompanying drawings, wherein like reference numerals designate like or corresponding parts throughout the several views, in which:

FIG. 1 is a schematic view of a lifting magnet device constructed in accordance with the teachings of the present invention and shown being suspended from a cargo crane;

FIG. 2 is a plan view of one embodiment of the lifting magnet device of the invention;

FIG. 3 is an elevational view, partly in section, of the lifting magnet device of FIG. 2;

FIG. 4 is a bottom view of one of the elongated pole pieces of the embodiment illustrated in FIGS. 2 and 3;

FIG. 5 is a schematic of a circuit for controlling the excitation of the energizing coils of the lifting magnet device of this invention;

FIGS. 6a and 6b are simplified perspective views illustrating two kinds of cargo lifting operations;

FIG. 7 is a side elevation of another embodiment of this invention;

FIG. 8 is a bottom view of one of the elongated pole pieces of the embodiment shown in FIG. 7;

FIG. 9 is a side elevation of still another embodiment of the present invention; and,

FIG. 10 is a bottom view of the device shown in FIG. 9.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to the drawings, and more particularly to FIG. 1 thereof, a traveling crane generally designated by the reference numeral 10 is disposed on rails 11 and 12 for movement in a direction perpendicular to the surface of the drawing paper, or parallel with the rails.

Conventionally, the traveling crane 10 includes a girder 13, a control room 14 integrally constructed with the girder, and a crab 15mounted on the girder for movement in a direction perpendicular to the path of movement of the traveling crane itself.

The crab carries a drum 16 for winding a steel rope, or cable 17, to lift a hook member 18 secured thereto, an electric hoisting motor l9'for driving the drum, an electromagnetic brake (not shown)'for clamping the hoisting motor to prevent free lowering of the cargo when the motor is at a standstill, a mechanical friction brake (not shown) arranged between the shaft of the motor 19 and the shaft of the drum 16 for absorbing the potential energy of the lowering load being applied by the weight of the cargo, and an electric traversing motor (also not shown) for driving the crab 15 along the girder 13.

Although it is not shown, a trolley wire is provided along one of the rails 11 and 12 for supplying the crane 10 with electrical power through a suitable connecting device (not shown) which slidably contacts the trolley wire, whereby electrical power may be taken into the crane as desired. The electric power taken into the crane is distributed through various controllers provided in the control room and control panel boards conventionally mounted on the girder 13 for the aforedescribed hoisting motor 19 and traversing motor, as well as for a traveling motor (not shown) mounted on the girder for driving the crane as desired.

A lifting magnet generally designated by the reference numeral is shown being suspended from the hook 18. To energize and control the magnet 20, there are mounted on the girder 13 a relatively constant voltage source 63, such as either an electric motor-generator or a static converter unit including a thyristor invertor and a thyristor rectifier, and a control panel board 64.

When the voltage being supplied to the trolley is from an A.C. power source, an A.C. induction motor may be employed as the driving motor of the motor-generator unit to drive a D.C. generator of the same. On the other hand, where the voltage for the trolley is supplied from a D.C. power source, a thyristor inverter is preferably employed to convert D.C. to A.C., then the A.C. voltage is rectified by the thyristor rectifier to energize the magnet. It will be readily understood that the constant voltage source 63 may include any suitable voltage regulating device for supplying a relatively constant output voltage to the energization circuit of the lifting magnet 20. This provision insures against any sudden decrease in the energization voltage level of the magnet due to voltage variations such as are likely to occur upon starting of the motors of the crane, whereby the cargos attracted to the magnet can thus be effectively prevented from being inadvertently dropped out of the magnet.

To conduct an exciting current to the lifting magnet 20, a flexible cable conductor 65, one end of which is wound around a cable drum 66 rotatably mounted on crab 15, is suspended from the crab to a cable connector 67 which is supported on the hook 18. Another cable 68, having one end electrically connected to the lower end of the cable 65 through the connector 67, is connected at its other end to a terminal box 69 mounted on the lifting magnet.

Although now shown, the shaft of the cable drum 66 is mechanically connected to that of the wire cable drum 16 through a gear train, whereby

cables

65 and 68 can be rolled up and down in synchronized relation with the hoisting and lowering activities of the hook 18.

The output of the control panel 64 is connected to a subtrolley wire 70 extending along the girder and the end of the cable conductor 65 wound around the cable drum 66 is slidably connected to the sub-trolley wire through a collector 71. The amplitude of the exciting current for the magnet 20 may be regulated by a regulating, or controller device 72, provided in the control room 14. A further function of this controller 72 will be described hereinafter.

Referring now to FIGS. 2 and 3 for an explanation of the structural detail of the lifting magnet 20, there is shown a framework 21 which acts as a yoke through which magnetic fluxes may be passed. The framework, or yoke, is preferably made of cast steel and is formed in a generally flat configuration. A pair of

cylindrical pole members

22 and 23 are integrally formed with the yoke member 21 and project downwardly from the lower surface thereof adjacent opposite ends along a lengthwise direction.

A main exciting coil 24 is concentrically wound around the cylindrical pole member 22, as shown in FIG. 3, and similarly, although not illustrated, another main exciting coil is concentrically wound around the cylindrical pole member 23.

Elongated

pole members

25 and 26 are provided below the lower ends of

cylindrical pole members

22 and 23 such that the longitudinal axes of the former are respectively positioned perpendicularly to the axes of the latter.

As is clearly shown in FIG. 2, the

elongated pole members

25 and 26 respectively include three elongated cast steel'

blocks

27, 28, 29 and 30, 31, 32 disposed in parallel, in which the centered blocks 27 and each are of a length longer than those of the other two blocks disposed on either side thereof for the reason described hereinbelow. Also, both

elongated pole members

25 and 26 have a length such that one of the ends thereof protrudes beyond the

opposite edge portions

33 and 34 of the yoke 21 to indicate their angular positions relative to the yoke,.

The three parts or blocks of each pole member are integrally assembled with each other by any suitable fixture means such as welding, and each pair of blocks disposed on opposite sides of the centered block have a vertical dimension which is less than that of the centered block, one of the same 31 being shown in FIG. 3. Furthermore, the lower surface of each of such pairs of blocks are positioned slightly higher than the lower surface of the centered block as also shown by the relative positioning of

blocks

30 and 31 in FIG. 3. The purpose of this arrangement will be set forth hereinafter. The amplitude of the total width of

elongated pole pieces

25 and 26 is chosen substantially equal to that of corresponding

cylindrical poles

22 and 23.

In FIG. 4, there is shown a bottom view of theelongated pole piece 25. Of course, because the other piece 26 also has the same construction as the piece 25, the explanation with a view thereof is omitted.

The centrally disposed block 27 has a rectangular slot 35 provided in the bottom surface thereof along and near the four edges of the same. As is shown in FIG. 3, there is embedded in this slot a formed coil 36 for the purpose of exciting the centered block. The opening of the slot receiving the exciting coil is then closed with wedges 37 inserted in the slot, whereby the formed coil is prevented from dropping out.

Because the

elongated pole members

25 and 26 are assembled on the yoke member in the same manner, respectively, only the method for assembling the elongated pole member 25 is disclosed in the drawing.

Thus, to assemble an elongated pole piece 25 with yoke member 21, there is provided an opening 38 vertically extending through the cylindrical pole member 22. A tubular member 39 with a flanged portion 40 at one end, preferably made of steel, is fixed to the centered area of the upper surface of the elongated pole piece 25 at the flanged portion 40.

Referring again to FIG. 4, there are provided a plurality of openings in the elongated pole piece 25, which openings extend therethrough from the bottom surface of the pole piece to the upper surface of the same and respectively receive therein a screw bolt 42. Thus, the threaded end of each bolt 42 is screwed into the flanged portion 40 of tubular member 39 to secure the elongated pole piece to the tubular member. Of course, the elongated pole piece can be fixed to the tubular member, by other suitable attachment methods, such as, for example, by welding.

A tubular portion 43 of tubular member 39 extends upward from the secured flange portion 40 through the opening 38 in the cylindrical pole member 22, and then further extends through an aligned opening 44 in a ring-shaped thrust collar 45, whereby the tubular member 39 is fixed at the tubular portion 43 thereof with the collar 45 by any suitable affixing means, such as bolts 46 extending through radial openings 47 through the wall of the collar.

Around the opening 38 in yoke member 21 and on an upper surface of the same is a thrust bearing seat 48 welded thereto to support the thrust force resulting from the weight of the elongated pole assembly, whereby the elongated pole piece 25 can be rotatably supported from the yoke member.

To rotate the elongated pole piece 25 around the central axis of tubular member 39, an operational arm 49 is securely mounted on collar member 45 by means of bolts 50, shown in FIG. 2, such that the arm is disposed on the ring-shaped collar along a diameter thereof and the opposite ends of the arm extend over the peripheral portion of the collar.

To cause the exciting current to flow through the coil 36 embedded in the slot 35 of the elongated pole piece, a cable conductor 51 is introduced into a terminal of the coil through an opening 52 in the arm 49 and an axially disposed cylindrical opening located within the tubular member 39 which is aligned therewith permitting the same to be connected to the coil terminal.

Similarly, an operational arm 53 is securely mounted on a collar member 54 connected to the elongated pole member 26 for causing it to rotate.

A pair of

arms

49 and 53 are thereby located in parallel, as shown, and their corresponding ends are respectively connected with each other by

elongate rods

55 and 56 having the same length. Thus, because the pair of

arms

49 and 53 and the pair of

rods

55 and 56 form a so-called four-link rocking mechanism, it is possible to rotate the pair of

elongated pole pieces

25 and 26 in desired parallel relation at all times.

To rotate the pair of

elongated pole members

25 and 26 around the central axes thereof, an electric motor-driven fluid actuator 57 is pivotally mounted on the upper surface of yoke member 21 by means of a pin member 60. The fluid actuator is a conventional oil pressure type actuator and includes a piston with a piston rod (not shown) reciprocally located in a cylinder 58, which, in turn, is filled with an oil. The cylinder has an impeller (not shown) to be driven by an electric motor 59 located at one end thereof. When the motor is rotated in one direction, the impeller generates an oil pressure which functions with the piston such that the same will be moved in one direction. On the other hand, where the motor drives the impeller in the reverse direction, the same will cause the piston to move in the reverse direction.

As is clearly shown in FIG. 3, the leftward end of the piston rod extends through the leftward end wall of the cylinder 58, where it rotatably engages a downward extension of a pin 61 mounted through one end of the arm 49 through a connection rod 62.

Thus, when the motor 59 is rotated forward, the piston rod of the actuator is pushed out from the cylinder thereof, rotating the arm 49 in a counterclockwise direction (see FIG. 2). The rotation of the arm 49 is transferred through the

rods

55 and 56 to the arm 53 to rotate it in the same direction by the same angle as the aforesaid arm 49.

Such synchronized movements of the pair of arms are transferred to the pair of

elongated pole pieces

25 and 26 through the tubular members 39 being connected between thearms and the pole pieces, respectively. In FIG. 3, only one of the tubular members 39 connected between arm 49 and pole piece 25 is shown, but the other arm 53 and pole piece 26 are also connected by a tubular member similar to the member 39.

It will be therefore readily understood that the pair of

elongated pole pieces

25 and 26 synchronously rotate in a counterclockwise direction during forward rotation of the motor 59.

On the contrary, when the motor 59 is rotated in a reverse direction, the aforesaid movement of the parts will occur in a reverse direction, whereby the pair of

pole pieces

26 and 26 will rotate in a clockwise direction as seen in FIG. 2.

In FIG. 5, there is shown a typical excitation circuit for the

main coils

24 and 124, respectively, wound about

cylindrical pole members

22 and 23, as well as for

coils

36 and 136 wound in slots 35 of

elongated pole members

25 and 26 as shown in FIG. 3.

One end terminal of each of the

coils

24, 124, 36 and 136 is connected together and then connected to a negative conductor, which, in turn, is connected through the terminal box 69 to a lead of the cable conductor 68 as shown in FIG. 1. The other terminals of

coils

36 and 136 are connected together at one point, and then connected through the terminal box 69 to a positive lead of cable conductor 68. The other terminals of

main coils

24 and 124 are also finally connected to the positive lead through the terminal box 69. However, this connection is made through normally open serially

connected switches

73 and 74.

The switch contact 73 closes when the hoisting operation begins and the contact 74 closes when a predetermined time interval elapses after the beginning of the hoisting operation. The contact 74 belongs to a timing relay 75 which functions when an electric signal corresponding to the beginning of the hoisting operation is received by the relay from the controller 72 through a conductor 76 connected to the control panel board 64. The series

circuit including contacts

73 and 74 connected is employed for selectively lifting cargos as described hereinafter.

To simultaneously excite all the coils, there is provided a normally open contact 77 connected across the series connected

contacts

73 and 74. This contact is closed when it is required that many cargos are lifted up at the same time as described hereinafter.

These

contacts

73, 74 and 77 and the timing relay 75 are mounted in the control panel board 64 and are controlled by the controller 72 located in the control room 14, as shown in FIG. 1

As is shown in FIGS. 2 and 3, the lifting magnet 20 is suspended from the hook 18 by means of four eye-bolts 78 secured onto the four corner portions of the surface of the yoke member 21.

In operation, let us assume that it is necessary to lift a plurality of cargos, such as I-beams 79 shown in FIGS. 6a and 6b, at the same time..This operation is readily performed by positioning the pair of

elongate magnets

25 and 26 on the beams such that the longitudinal axes of the magnets are disposed perpendicular to those of the l-beams as shown in FIG. 6a. This is made by rotating the elongate magnets from the positions shown in FIG. 2 to angular positions perpendicular thereto. The control of the rotation for the elongate magnets is maintained by the electric motor driven oil pressure actuator 57 to which the control signal is given from the controller 72 in the control room 14 through the control panel board 64.

In this case, the contact 77 is closed, whereby all of the

coils

24, 124, 36 and 136 are fully excited at the same time. The lifting magnet 20 will therefore generate a full rated output to magnetically attract many of the cargos.

The magnetic fluxes induced by each pair of

coils

24 and 36, as well as

coils

124 and 136, are respectively added to each other in the respective pole members, and the fluxes, for example, flow out from the pole face of one of the poles 25, then through the cargos made of magnetic material, flowing into the other pole 26, and then through the yoke member 21 so as to return back to the aforesaid pole 25.

The cargo handling operation as mentioned above is employed with the usual loading of cargos on a truck or a ship and is further employed to change the cargos from one place to the other in which the same'are to be loaded.

For example, upon the loading of a truck, assume that only a little space remains for loading only one or two l-beams thereon.

The pair of

elongate magnets

25 and 26 are rotated to the position shown in FIGS. 2 and 6 by the oil pressure actuator 57 which may be driven by the electric driving motor 59 thereof under the control of the controller 72 through the control panel board 64. The angular positions of the pair of

magnets

25 and 26 can be visibly established since one end of each extends over the edge portion of the yoke member 21 and may be observed from the operation room 14 of the cargo crane.

Such rotative motion of the

elongate magnets

25 and 26 can also be initiated by a manually operable switch such as a pendant type reversible switch 80 suspended from the terminal box 69 of the lifting magnet 20.

Assume now that the pair of

elongate magnets

25 and 26 have been positioned on an I-beam 79 such that their longitudinal axes are aligned with each other along the longitudinal axis of a beam, as shown in FIG. 6b.

When the hoisting control order is emanated from the controller 72, only the pair of

coils

36 and 136 of the elongated magnets are at first energized from the control panel, starting the hoisting operation of the beam and the contact 73 will close responsive to the hoisting operation, as will be understood from the circuitry illustrated in FIG. 5.

After a predetermined time delay following the initiation of the hoisting of the beam, the relay 75 is operative to close the contact 74 thereof, whereby the pair of

main coils

24 and 124 are energized such that the magnetic fluxes emanated therefrom are added to those of the corresponding elongated coils to increase the magnetically attractive forces to be generated by the latter.

Thus, it may be readily understood that prevention of drop out of the I-beam from the lifting device during the lifting operation may be achieved with the present invention. In this way, also, a single I-beam can be handled in loading the same on the truck.

It can be, however, easily understood that by rotating the pair of elongate magnets by any other angle in a plane, it is possible to lift any desired number of beams less than the maximum number capable of being lifted.

As shown in FIGS. 2 and 3, each of the elongated pole members and 26 includes a

centered part

27 and 30 and a pair of

side parts

28, 29 and 31, 32, located respectively along opposite side walls of the centered parts. The lower surfaces of the aforesaid side parts are in a slightly higher level than those of the centered parts. This insures that when only the

coils

36 and 136 of the elongated pole pieces are excited for lifting only a single .l-beam, the clearance provided between the aforesaid lower surfaces of the side parts and the upper surface of the cargo provides a relatively high magnetic reluctance for the magnetic fluxes which may flow therethrough, whereby it is possible to select only one l-beam to be lifted.

In another embodiment illustrated in FIG. 7, the lifting magnet 20 includes a pair of

elongated pole members

25 and 26 mounted on a yoke member 21 such that they can rotate around the central axes thereof. The rotation of the pole members are provided by

electric motors

81 and 82 which, in turn, provide reversible torques for the elongated pole members through

worms

83 and 84 secured to one end of the shafts of the motors and section gears 85 and 86 mounted partially around the peripheral portions of

collar members

45 and 54. The collar members have a construction similar to those of FIGS. 2 and 3, except for the provision in this embodiment of the sector gears being mounted on the same.

Further, the lifting magnet disclosed herein does not include main coils as shown in FIGS. 2 and 3. This serves to handle cargos which are relatively light in weight compared with those being lifted with the device described in FIGS. 2 and 3.

FIG. 8 shows an enlarged bottom view of one of the elongated poles of the embodiment illustrated in FIG. 7. The elongated pole member 25 includes a centered part made of cast

steel having slots

87 and 88 adjacent to longitudinally opposite ends thereof for receiving two coil sides ofa formed coil. The other two coil sides are mounted along the other opposite side walls in a lengthwise direction of the centered part, and are covered by elongated side parts 89 and 90 made of cast steel to protect the same. The openings of the slots and the openings of the side slots constructed between the centered part and the side cover parts are covered by wedges 100 inserted therein. The two side parts are integrally secured with the centered part by employing any suitable means such as welding and bolting. The elongated pole member 25 is secured by welding to a lower surface of a cylindrical support 101 made of cast steel and the same serves not only to support the pole member on the yoke member, but also magnetically connects both members.

In accordance with this embodiment, the exciting coils can be easily mounted on the elongated pole members without specially machining the same along their lengthwise directions to provide the slots for receiving the elongate coil sides.

Also, because the rotation of the pair of elongated pole members is separately controlled by the separated

electric motors

81 and 82, the complicated mechanical interconnection which usually is required between the pole members can be eliminated, and the entire driving mechanism for the pole members thus becomes more simple and less expensive. At the same time, however, the angular positions of the pole members can still be easily observed and controlled either in the control room of the crane or from a place on the earth.

A further embodiment of the invention is shown in FIGS. 9 and 10, in which a substantially single elongated pole member 125 is provided. The pole member 125 includes a centered part 102 and a pair of side parts 103 and 104 located along the lengthwise-extending side walls of the centered part, and these three parts are made of cast steel or thick steel sheets, respectivel As best shown in FIG. 9, the centered part 102 is provided with an integral cylindrical support member 105 on the upper surface thereof substantially intermediate its ends such that the same extends upwards from the centered part. The cylindrical support extends through an opening 106 of a supporting frame 107 and the top portion thereof fits into an opening 108 of a collar member 109 and is secured thereto by means of screw rod members 110. A plurality of thrust balls 111 are positioned between the bottom surface of the collar 109 and the upper surface of the frame 107 in corresponding ring-like grooves respectively provided in the aforesaid surfaces.

An electric motor 112 is mounted on the frame 107 and by causing a worm 113 thereof to engage with a sector gear 114 secured around the side wall of the collar member 109, rotating the motor makes possible the rotation of the elongated pole member 125 such that the same will assume a desired angular position in a horizontal plane.

Referring to FIG. 10 in which the bottom view of FIG. 9 is shown, there are shown a plurality of coils 115 to posi tioned in spaced-apart relation along a lengthwise direction of the elongated pole member 125. Each coil side of the coils is placed in a respective slot to 141 which is machined in a direction perpendicular to the lengthwise of the pole member. The respective other two coil sides of each of the coils are positioned along the longitudinal side walls of the centered part 102, and are respectively covered by side parts 103 and 104 to protect the coil sides from, among other things, objects which may hit the coil sides. In the drawing, for the convenience of easily viewing the coils, the wedges generally inserted for retaining the coils have been removed.

There are provided magnetic poles 142 and 149 in areas surrounded by coils such that they alternatively show north pole and south pole. It is therefore understood that magnetic fluxes emanated from one pole surface enter into the cargo made of magnetic material, flow therethrough, enter into the adjacent pole via the surface thereof, and after that flow through the back portion of the centered part into the originated pole. Thus, the centered part 102 serves as a yoke member having a plurality of magnetic poles.

To prevent reducing the effective magnetic fluxes, the lower surfaces of both side parts 103 and 104 are positioned in a plane slightly higher than the lower surface of the centered part. In this way, because there are defined air gaps between the lower surfaces of both side parts and the upper surface of cargo, the magnetic reluctance in the gaps is increased.

The lifting magnet as shown in FIGS. 9 and 10 can be effectively employed for handling cargos such as l-beams H-beams and the like, which have a relatively short length.

Obviously, many modifications and variations of the present invention are possible in light of the teachings of the present invention. Accordingly, although the invention has been explained by way of example for handling I-beams, l-I-beams and the like, it should be apparent that the invention can be readily adapted for handling other things such as scrap iron, ingots, billets, sheet bars, wires and rods. Additionally, the invention can be also adapted for an operation such as turning over the sheet bar. It is therefore to be understood that within the scope of the teachings herein and the appended claims, the invention may be practiced otherwise than as specifically described herein.

1. A lifting magnet for handling cargos comprising:

a frame member suspended from a crane being made of magnetic material and serving as a magnetic yoke through which magnetic fluxes are permitted to flow,

a pair of elongated magnetic pole members rotatably mounted on said frame member for being rotated in a plane relative to the frame member and being disposed thereon with the functioning surfaces thereof directed toward cargos to be lifted thereby.

What is claimed and desired to be secured by Letters Patent I a first exciting coil means respectively wound on each of said elongated pole members,

a second exciting coil means mounted on said frame member for increasing the magnetic flux being emanated from said first coil means when used in combination therewith,

control means connected to feed exciting currents to said first and second exciting coil means, and

rotating means mounted on said frame member to cause said elongated magnetic pole members to rotate in said plane.

whereby when said pair of elongated pole members are positioned on a selected elongated cargo such that the lengthwise axes of the pair of pole members are aligned with the lengthwise direction of the cargo and a lifting operation of the cargo is initiated, said control means initially energizes only said first exciting coil means and subsequentlyenergizes said second exciting coil means so as to add magnetic fluxes emanated therefrom to those of said first coil means after starting the lifting operation of the cargo.

2. A lifting magnet for handling cargos according to claim 1,

wherein said rotating means comprises:

a link mechanism connected between said pair of pole members for simultaneously rotating the pole. members, and

a driving means mounted on said frame member to rotate said pair of pole members through said link mechanism.

3. A lifting magnet for handling cargos according to claim 2,

wherein said driving means is an electric motor-driven oil pressure actuator.

4. A lifting magnet for handling cargos according to claim 1,

wherein said control means includes means responsive to the start of the cargo lifting operation and a timing relay means operable after a predetermined interval of time elapses following the start of said lifting operation,

whereby said second exciting coil means is energized through the cooperation of said operation starting responsive means and said timing relay means for energizing said second exciting coil said predetermined interval of time after energizing said first exciting coil. 5. A lifting magnet for handling cargos comprising: a frame member which is suspended from a crane, at least one elongated magnetic member rotatably mounted on said frame member for being rotated in a plane relative to the frame member and being disposed thereon with the functioning surface thereof directed toward cargos to be lifted thereby, and rotating means mounted on said frame member to cause said at least one elongated magnetic member to rotate in said plane, said at least one elongated magnetic member being in three parts respectively made of magnetic material including an elongated center part and side parts located along lengthwise opposite side walls of the center part, said center part including a plurality of slots located perpendicularly to said lengthwise direction and being spaced apart for receiving two opposite coil sides of an exciting coil therein, the other two opposite coil sides of said exciting coil being located along the lengthwise opposite walls of said center part, and said side parts respectively covering said other two opposite coil sides for protecting the same. 6. A lifting magnet for handling cargos according to claim 5, wherein Y the lower surfaces of said two side parts of said at least one elongated magnetic member facing said cargos is disposed at a higher level relative to said cargo than the corresponding lower surface of said center part. 7. A lifting magnet for handling cargos according to claim 1, wherein at least one end of each of said elongated magnetic pole members extends over the peripheral edge of said frame member to indicate the angular position thereof when said magnetic pole members are rotated in a plane relative to said frame member.

Claims

1. A lifting magnet for handling cargos comprising: a frame member suspended from a crane being made of magnetic material and serving as a magnetic yoke through which magnetic fluxes are permitted to flow, a pair of elongated magnetic pole members rotatably mounted on said frame member for being rotated in a plane relative to the frame member and being disposed thereon with the functioning surfaces thereof directed toward cargos to be lifted thereby. a first exciting coil means respectively wound on each of said elongated pole members, a second exciting coil means mounted on said frame member for increasing the magnetic flux being emanated from said first coil means when used in combination therewith, control means connected to feed exciting currents to said first and second exciting coil means, and rotating means mounted on said frame member to cause said elongated magnetic pole members to rotate in said plane. whereby when said pair of elongated pole members are positioned on a selected elongated cargo such that the lengthwise axes of the pair of pole members are aligned with the lengthwise direction of the cargo and a lifting operation of the cargo is initiated, said control means initially energizes only said first exciting coil means and subsequently energizes said second exciting coil means so as to add magnetic fluxes emanated therefrom to those of said first coil means after starting the lifting operation of the cargo.

2. A lifting magnet for handling cargos according to claim 1, wherein said rotating means comprises: a link mechanism connected between said pair of pole members for simultaneously rotating the pole members, and a driving means mounted on said frame member to rotate said pair of pole members through said link mechanism.

3. A lifting magnet for handling cargos according to claim 2, wherein said driving means is an electric motor-driven oil pressure actuator.

4. A lifting magnet for handling cargos according to claim 1, wherein said control means includes means responsive to the start of the cargo lifting operation and a timing relay means operable after a predetermined interval of time elapses following the start of said lifting operation, whereby said second exciting coil means is energized through the cooperation of said operation starting responsive means and said timing relay means for energizing said second exciting coil said predetermined interval of time after energizing said first exciting coil.

5. A lifting magnet for handling cargos comprisiNg: a frame member which is suspended from a crane, at least one elongated magnetic member rotatably mounted on said frame member for being rotated in a plane relative to the frame member and being disposed thereon with the functioning surface thereof directed toward cargos to be lifted thereby, and rotating means mounted on said frame member to cause said at least one elongated magnetic member to rotate in said plane, said at least one elongated magnetic member being in three parts respectively made of magnetic material including an elongated center part and side parts located along lengthwise opposite side walls of the center part, said center part including a plurality of slots located perpendicularly to said lengthwise direction and being spaced apart for receiving two opposite coil sides of an exciting coil therein, the other two opposite coil sides of said exciting coil being located along the lengthwise opposite walls of said center part, and said side parts respectively covering said other two opposite coil sides for protecting the same.

6. A lifting magnet for handling cargos according to claim 5, wherein the lower surfaces of said two side parts of said at least one elongated magnetic member facing said cargos is disposed at a higher level relative to said cargo than the corresponding lower surface of said center part.

7. A lifting magnet for handling cargos according to claim 1, wherein at least one end of each of said elongated magnetic pole members extends over the peripheral edge of said frame member to indicate the angular position thereof when said magnetic pole members are rotated in a plane relative to said frame member.