US3015045A

US3015045A - Lifting magnet

Info

Publication number: US3015045A
Application number: US778247A
Authority: US
Inventors: Arthur L Ward
Original assignee: Square D Co
Current assignee: Schneider Electric USA Inc
Priority date: 1958-12-04
Filing date: 1958-12-04
Publication date: 1961-12-26
Anticipated expiration: 1978-12-26

Description

Dec. 26, 1961 ARTHUR L WARD A. L. WARD LIFTING MAGNET Dec. 26, 1961 3 Sheets-Sheet 2 Filed Dec, 4, 1958 MII /&\\\\\\\\\ IN VEN TOR.

ARTHUR L.. WARD A. L. WARD LIFTING MAGNET Dec. 26, 1961 3 Sheets-Sheet 3 Filed DeC. 4, 1958 INVENTOR.

ARTHUR L.. WARD c/lz. ITV- ,Kal

Patented Dec. 26, 1961 3,015,045 LIFTING MAGNET Arthur L. Ward, Cleveland, Ohio, assigner to Square D Company, Detroit, Mich., a corporation of Michigan Filed Dec. 4, 1958, Ser. No. 778,247 7 Claims. (Cl. 317-164) This invention relates to lifting magnets and in particular to lifting magnets for lifting and handling coils having a plurality of convolutions of magnetic sheet material including coils in which each convolution of magnetic sheet material is spaced from its next adjacent convolution of magnetic material.

In coils of magnetic sheet metal, rod stock, and the like, since the circumferential length of each convolution is less than the circumferential length of the next adjacent convolution outwardly therefrom, the weight of the convolutions is increscent progressively from the innermost to the outermost convolution. In some coils the convolutions are juxtaposed tightly against each other and in other coils the convolutions of magnetic sheet material are spaced from each other, the spaces therebetween forming, in effect, convolutions of non-magnetic material. ln some instances, these spaces may be filled with non-magnetic material, for example, paper, brass, nylon, or other similar materials.

In the past magnets for lifting coils have been constructed to thread circumferentially through the convolutions of the coil. However, in these magnets the amount of flux passing through any particular convolution of magnetic material, was in no way proportional to the weight or circumferential length of that convolution. Examples of prior lifting magnets are illustrated in Patents Nos. 2,220,561 issued to A. L. Ward, 2,545,356 and 2,140,700 issued to H. E. Hodgson. Attempts were made to align several individual magnets at spaced intervals about a circle so that they `would engage the ends of edges of the convolutions of the coil. In these prior magnets the windings in the magnets were circular and modified rectangular pole shoes extended generally radially of the coil being lifted. Alternate pole shoes were of one polarity and the remaining pole shoes were of the opposite polarity so that the lines of flux would thread from one pole shoe arcuately through the coil to the pole shoe on the next adjacent magnet.

In some instances it is desired to lift coils wherein the convolutions of magnetic material are spaced or separated from each other with the space between adjacent convolutions of magnetic material occupied by non-magnetic material, and wherein the spacing between the convolutions of magnetic material is maintained throughout the handling and lifting thereof. Attempts were made to use rectangular shaped lifting magnets arranged at spaced intervals about a circle with the longitudinal axis of the magnets extending radially of the coil and its convolutions during lifting. These magnets were not completely satisfactory for several reasons. First of all, if each rectangular magnet was made strong enough to lift the outer convolutions, it had more lifting power than was necessary to life the innermost convolution which would be reached by the magnet. Furthermore, the inner ends of the magnets formed a configuration of a modified circle of radius or cross dimension greater than the radius of the innermost convolution to be lifted when the magnet was powerful enough to lift the outer convolution. On the other hand, if the magnets were made of smaller width so that they could engage the innermost convolutions, they were not powerful enough to lift the outermost convolutions.

It has been found that the capacity of magnets for lifting coils may be increased and that spaced convolutions may be held in spaced relationship with each other if the pole shoes are spaced close together and if there is a proportioning between the contact length of each pole shoe and the respective convolution being lifted.

One of the objects of the present invention is to overcome the aforementioned problems and the deficiencies in prior lifting magnets designed for lifting coils.

Another object of the invention is to provide a magnetic circuit comprising a coil having convolutions of magnetic sheet material and a lifting magnet having pole faces in flux conducting relationship with an edge of each of the convolutions wherein magnetic flux is threaded generally circumferentially in each convolution of the coil, and the circumferential extent of the pole faces are such that the ratio of the amount of flux in each convolution relative to the circumferential length of that convolution is substantially the same for substantially all convolutions of the coil, whereby the total ux is proportioned among the convolutions in relation to their respective weightsthe heavier the convolution, the greater the amount of flux applied thereto.

A further object of the invention is to provide a lifting magnet in which the pole faces are spaced from -each other about a common axis, and in which the total width circumferentially of the axis of the pole faces is so increscent from the inner coil engaging limit to the outer coil engaging limit of the pole face that the ratio of the total width of the faces at each increment of distance outwardly from the axis relative to the circumference defined by a radius equal to the distance of that increment from the axis is the same for all increments of distance outwardly from the axis.

A still further object of the invention is to provide a lifting magnet which has a plurality of primary pole faces, each provided with a pair of secondary pole faces, one on each side of the primary pole face, and all arranged for simultaneous contact with the edge of the convolutions of a coil, the pole faces having a width wherein the length of contact, or length of magnetic attraction, between the face and each convolution is different than the length of contact between that respective face and the other convolutions and wherein the lengths of contact are at least approximately proportional to the arcuate length of each convolution.

A further object of the invention is to provide a lifting magnet for handling coils having convolutions spaced apart which is constructed from a plurality of similar individual magnets arranged in a circle so that the lifting magnet may be easily constructed from components economically shipped and assembled at the job site.

Other objects and a fuller understanding of this invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawings, in which:

FIG. l is a top View of a lifting magnet incorporating the features of the invention resting on a coil to be lifted;

FIG. 2 is an enlarged vertical sectional view taken approximately along the line 2-2 of FIG. l;

FIG. 3 is a sectional view taken approximately along the line 3 3 of FIG. 2; and

FIG. 4 is an illustration representing the design of the surfaces of the pole shoes of one of the electromagnets in relation to the coil.

A preferred embodiment of the invention has been illustrated in the drawings for the purpose of exemplification and not for the purpose of limiting the scope of the invention to the details of construction illustrated. In this preferred embodiment there is illustrated a lifting magnet 10 for lifting coils 11 having convolutions of magnetic material.

The magnet will be described in combination with coils in which the convolutions of magnetic materials are spaced apart since the problem of lifting such coils was the basis of the present invention. However, it is understood that the lifting magnet will lift coils in which the convolutions of magnetic material are in surface contact.

The coil 11 comprises or has a plurality of magnetic convolutions of magnetizable sheet material, for example, iron, including an inner convolution 12, an outer convolution 13 and one or more intermediate convolutions 14, the magnetic convolutions being spaced from each other so that magnetic flux does not readily flow radially of the coil from one convolution to the next adjacent convolution. ln coils of this type there is an extremely high, if not infinite resistance to the flow of magnetic flux from one convolution to a next adjacent convolution in a direction radially of the coil, and an extremely low resistance or a high conductance to the flow of magnetic flux circumferentially of the convolution. The space between the separate magnetic convolutions are at least partially filled with a material of low or non-magnetic material, such for example, air, gas, nylon, brass, copper, etc.

For purposes of clarity, and because, in this instance, air and paper or other non-magnetic materials have similar characteristics relative to the magnetic convolutions, the non-magnetic material between the respective magnetic convolutions is illustrated as space and is not cross sectioned or numbered in the drawings.

The magnet 1t) comprises a plurality of individual electro magnets 1S arranged at spaced intervals about a circle and supported by a suitable supporting structure or spider 16. ln FIG. l, the lifting magnet is illustrated as having six electromagnets 15 or groups, each group including a pair of secondary poles and a primary pole disposed therebetween, supported by the spider 16 so that at least two of the magnets have a common longitudinal axis extendable diametrically across a coil 11 to be lifted. Since all of the individual electromagnets may be similar or identical only one will be described in further detail.

As best illustrated in FIGS. 2 and 3 each electromagnet 15 comprises a housing 20 of modified E-shape in cross section to provide a center or primary pole 21 of one polarity and a pair of outer or

secondary poles

22 and 22 of the opposite polarity. The

secondary poles

22 and 22 are spaced from the center pole 21 and this space is lled with an electrically energizable winding 23 which may be connected by suitable leads 24 extending through the top 25 of the housing 20 and into a terminal device 24 for connecting the coil to a suitable source of power (not shown). The winding 23 and the inner pole 21 are covered on the bottom side thereof by a retaining plate 26 which holds the winding 23 within the housing and between the primary and secondary poles.

The center or primary pole 21 and the outer or

secondary poles

22 and 22 are provided with pole shoes 27, 28, and 28', respectively. The shoes 28 and 28' may be integral with poles 22 and 22', if desired. These pole shoes 27, 2S, and 28', respectively, have

bottom surfaces

127, 128 and 128 which engage, or at least are within magnetic attraction distances of, the edges of the convolutions of the coil 11 being lifted. The surface 127 of the pole shoe 27 is wider at one end 29 than it is at the other end 3l). Similarly, the width of the surface of each of the outer shoes 28 and 2liV is greater at one end 31 or 31' than at the

other end

32 or 32 thereof, respectively. The surfaces 128 and 128' also are spaced equidistant from the surface 27 at least substantially throughout the length thereof.

The groups or electromagnets 15 are aligned by the spider 16 in such manner that all of the

shoes

27, 28 and 28 extend generally radially outwardly from the center of the magnet so that the longitudinal axis of the primary shoes extend at least approximately radially of a coil to be'lifted andV so that each shoe engages the inner,

outer, and

intermediate convolutions

12, 13, and 14 of the coil. In this way magnetic flux produced by the winding 23 threads through the surface 127 of the primary shoe 27, circumferentially through each magnetic convolution of coil 11 and through the surfaces 123 and 128 of the secondary shoes 2? and 28, the magnetic flux path being completed by the top 25 of 'the housing 20. The individual electromagnets or groups 15 may be energized so that each secondary shoe of each group is of the same polarity as the secondary poles of the group adjacent to it or the groups may be energized so that the primary poles of all of the individual groups or electromagncts 15 are of the Same or opposite polarity with respect to each other.

he spider 16 comprises a pair of spaced center plates and 41 provided with radially extending beams 42, one for cach electromagnet 15. The spider is further provided with chain fastening members 42' extending upwardly therefrom to provide for the attachment of suitable hoisting chains (not illustrated) to the spider. As best illustrated in FIGS. l and 2 each beam extends radially of the spider and generally along the longitudinal axis of its respective electromagnet 15. Each electromagnet 1S is provided with a plurality of upstanding ears 43 extending upwardly from the top 25 of the housing 20 and arranged for securement to the respective beams by pins 44 or other suitable fastening means. ln this instance it has been found desirable to have a pair of ears at each end of the housing with one ear on each side of the beam so that each pin extends through a pair of ears and the beam.

It is thus apparent that the lifting magnet 10, as illustrated herein has provided a structure capable of lifting coils 11 of magnetizable material in which each magnetic convolution of the coil being lifted is spaced from its next adjacent magnetic convolution. The magnet has a plurality of elongated primary shoes 27, each having a primary pole face 127 for contacting the coil. Each of these primary pole faces 127 has a narrow Width at one end or coil engaging limit 30 of the primary shoe 27, and a wide width at the end or coil energizing limit 29 of the primary shoe 27, with the width of the primary pole face 127 between the

ends

29 and 30 thereof gradually and uniformly increasing from the small width end 3l) to the large width end 29. In this instance the primary pole face 127 is bounded by radius lines extending outwardly from the center C of the lifting magnet 10. :The width of the pole face on each of the primary shoes increases uniformly from the narrow to the Wide end approximately in proportion to the distance from the center of the magnet, or from the center of the coil being lifted and thus approximately in proportion to the increase in weight of the convolutions being lifted.

It is further noted that the supporting spider 16 supports the primary shoes 27 with their pole faces 127 disposed at least substantially in a common plane and with the pole faces aligned with their narrow width ends 30 closer to each other than their wide width ends 29 and with the pole faces 127 spaced from each other. rl`he

secondary shoes

28 and 23 have their respective secondary pole faces 128 and 128 in the same plane as the primary pole faces 127. The narrow ends 32 and 32 of the secondary pole faces 128 and 128 are disposed adjacent to the ends 30 of the primary pole faces 127, respectively. Thus, with the construction herein described, the pole faces are thus spaced from each other about a coinmon axis and are adapted to engage the end of a coil of magnetic material in approximately coaxial relation to the convolutions thereof.

The total Width circumferentially of the axis of the pole faces is so increscent from the inner coil engaging limit to the outer coil engaging limit that the ratio of the total width of the faces at each increment of distance outwardly from the axis and relative to the circumference defined by a radius'equal to the' distance of the said incrementfrom the axis is the same for all increments of distance outwardly from the axis. In addition, the combined widths of the secondary shoe faces in a direction circumferentially of, and at a particular convolution, is illustrated as being at least approximately equal to the width of the primary shoe face in a direction circumferentially of and at that same convolution. It is further noted that both ends of each secondary shoe is spaced substantially equidistant from the respective ends of its respective primary shoe since the space therebetween is determined -by the dimensions of the Winding 23.

In using the magnet the operator first rests the magnet on top of a coil 11 to be lifted, with the magnet 1t) approximately centered on the coil so that each of the inner pole shoes 27 extend at least approximately radially of the coil and thus engage the respective edges of all of the spaced convolutions in the coil. At this time the magnet and coil have a magnetic circuit in which the pole faces of the magnet are in ux conducting relationship with an edge of each of the convolutions of the coil. Upon energization of the magnet the pole faces thread magnetic flux generally circumferentially in each convolution of the coil. The circumferential extent of the pole faces is such that the ratio of the amount of flux in each convolution relative to the circumferential length of that convolution is substantially the same for substantially all convolutions of the coil.

The magnetic convolutions of the coil are maintained in spaced relation and lines of flux flow lengthwise through each convolution for a short distance as compared to the total circumferential length of that convolution and between the primary and its respective secondary shoes or poles of each electromagnet, thereby substantially completely eliminating any forces which would tend to force the convolutions towards or away from each other.

Although this invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

Having thus described my invention, I claim:

1. A lifting magnet for lifting coils having convolutions of magnetizable material in which each said convolution of the coil being lifted is spaced from its next adjacent of said convolutions, said magnet comprising a plurality of elongated primary shoes each having a primary pole face for contacting the coil, each of said primary pole faces having a narrow width at one end of said primary shoe and a wide width at the other end of the primary shoe with the Width of the primary pole face between said ends gradually and uniformly increasing from the narrow width end to the wide Width end, means supporting said plurality of primary shoes with their pole faces disposed at least substantially in a common plane and with the pole faces aligned with their narrow width ends closer to each other than their wide width ends and with the pole faces spaced from each other, shoe energizing means to establish magnetic flux in flux paths extending transversely to and through the pole face of each respective primary shoe, pairs of secondary shoes arranged with a different pair for each primary shoe, each of said pairs having respective secondary pole faces in the same plane as their associated primary pole face, each primary pole face being disposed between its associated secondary pole faces, each of said secondary pole faces having a narrow width at one end thereof and a wide width at the other end thereof with the end having the narrow width disposed adjacent to the narrow width end of its associated primary shoe and with both ends of each secondary shoe spaced substantially equidistant from the corresponding respective ends of its associated primary shoe, and metallic magnetic flux conducting path means interconnecting each said primary shoe with its associated pair of secondary shoes at a distance from said pole faces to provide a closed circuit for magnetic flux passing through the pole faces and the convolutions of the coil when the primary pole shoes of the magnet are energized and the pole faces are in contact with the coil to be lifted.

2. In a lifting magnet for lifting coils having spaced apart convolutions of magnetizable material, a plurality of substantially identical individual electromagnets, each of said electromagnets comprising an elongated primary pole of one polarity and at least one elongated secondary poie of polarity opposite from said one polarity, said poles each having a bottom coil engaging surface wider at one end than the other, and magnetic ux conducting means connecting said primary pole to said secondary pole and retaining said secondary pole adjacent to and in spaced relation to said primary pole, supporting structure means for supporting said plurality of electromagnets in circumferentially spaced radially extending circular arrangement about a common axis with said wider ends of said coil engaging surfaces of said poles outermost, the space between the coil engaging surfaces of the secondary pole and the primary pole of each of said electromagnets being of uniform width throughout the major part of the radial length of said surfaces, and means for energizing each of said electromagnets.'

3. A lifting magnet according to claim 2 and wherein the means for energizing said electromagnets is such that the primary poles of adjacent electromagnets are of opposite polarity.

4. A lifting magnet according to claim 2 wherein said electromagnets are circumferentially spaced apart throughout the major part of their radial length a greater distance than said space between the coil engaging surfaces of the primary pole and secondary pole of each elcctromagnet.

5. A lifting magnet according to claim 2 wherein the means for energizing said electromagnets is such that the primary portion of adjacent electromagnets are of the same polarity.

6. A composite lifting magnet for lifting a helical coil of magnetizable sheet material of uniform width and thickness and having a plurality of convolutions with substanially equal spaces therebetween, and comprising a plurality of mechanically interconnected, magnetically, independent magnets each having at least a pair of elongated pole faces of opposite polarity, each of said pole faces being wider at one end than the other end and tapering gradually between its ends, said pole faces being in a common plane about a common axis and extending lengthwise approximately radially of the axis and being spaced apart with respect to each other circumferentially of the axis, and each being of such shape that, upon placing each of said pole faces in flux-conducting relationship with an edge of each convolution of said coil, the circumferential extent of each of the pole faces at each convolution is such that the ratio of the amount of Hux in each convolution relative to the circumferential length of that convolution is substantially the same for substantially all convolutions of said coil, and means for energizing the magnets.

7. The structure as dei-ined in claim 1 wherein said primary shoes are responsive to the energizing means, and the energizing means comprise windings on the primary shoes, respectively, and each winding fills the spaces between its associated primary shoe and the secondary shoes adjacent to its associated primary shoe.

References Cited in the file of this patent UNITED STATES PATENTS 2,220,561 Ward Nov. 5, 1940 2,545,356 Hodgson Mar. 13, 1951 FOREIGN PATENTS 607,637 Great Britain Sept. 2, 1948