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Publication numberUS3805978 A
Publication typeGrant
Publication dateApr 23, 1974
Filing dateJan 5, 1973
Priority dateJan 6, 1972
Also published asDE2300280A1
Publication numberUS 3805978 A, US 3805978A, US-A-3805978, US3805978 A, US3805978A
InventorsHahne G
Original AssigneeNielsen & Son Maskinfab As H
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Transport apparatus
US 3805978 A
Abstract
Automatic transport apparatus, especially a gantry crane, provided with a magnet beam for lifting and transporting steel sheets in a sheet stack. From the magnet beam a series of inter-spaced magnet beam sections is suspended, the sections being situated in an oblique plan forming an angle to the surface of the sheets in the sheet stack. The transport apparatus is able to lift the topmost sheet of a stack of sheets containing large sheets of various lengths, widths, and thicknesses. Each section has an oblong magnet which is pivotally journalled around a horizontal axis and is capable of activating a micro-switch.
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Description  (OCR text may contain errors)

United States Patent Hahne Apr. 23, 1974 TRANSPORT APPARATUS 3,486,784 12/1969 Ejlertsen 294/655 [75] Inventor: Gustav Adolf Hahne, Oelstykke,

Denmark Primary Examiner-Gerald M. Forlenza Assistant Examiner-George F. Abraham [73] Assignee: H. Nielsen & Son Maskmfabrik AlS, Attorney Agent or Firm Bmwne Beveridge,

Herlev, Denmark Grandi & Kline [22] Filed: Jan. 5, 1973 [21] Appl. No.: 321,402 [57] ABSTRACT Automatic transport apparatus, especially a gantry [30] Foreign Application Priority Data crane, provided with a magnet beam for lifting and Jun. 6, 1972 Great Britain 712/72 transporting steel Sheets in a Sheet stack' From the magnet beam :1 series of inter-spaced magnet beam [52] US. Cl. 214/85 D, 214/] BT, 214/658, tiOns is suspended, the sections being situated in an 294/655 oblique plan forming an angle to the surface of the 1511 1111.01. B66c 1/04 Sheets the Sheet stack- The transport apparatus is 5 Field of Search n 214 5 D, 1 BS 1 BTy able to lift the topmost sheet Of a stack Of sheets COD- 214/658; 294/655 taining large sheets of various lengths, widths, and thicknesses. Each section has an oblong magnet which [56] References Cited is pivotally journalled around a horizontal axis and is UNITED STATES PATENTS capable of activating a micro-switch.

2,565,927 8/1951 Morgan 214/1 BT X 12 Claims, 9 Drawing Figures mm mm mm 5 g m .W4 E m, WMHL i y 3 8 E T'ATENTED APR 2 3 I974 PATENTEBAPR 23 I974 8 805; 978

saw 2 [IF 5 T ATENTED APR 2 3 $974 SHEET 4 OF 5 JAHENTEMW 23 5% WEE? 5 [INF 5 TRANSPORT APPARATUS The invention relates to a transport apparatus, especially a gantry crane, provided with a magnet beam for lifting and transporting sheets of magnetizable material, especially steel sheets, which magnet beam has a girder and at least one from the girder by means of wires suspended magnet beam section, which has a frame with a front and a rear transverse frame part and two sidegoing frame parts, and one or more electro magnets mounted in the frame.

BACKGROUND OF THE INVENTION A transport apparatus a so-called captivator is known in the form of a wagon with a conveyor and a magnet beam of the above-mentioned kind, arranged to be capable of lifting single sheets from a stack of sheets. Such lifting of single sheets is needed in shipbuilding yards, rolling mills and other undertakings where sheets are processed. Such a transport apparatus with a magnet beam is to be designed in such a way that the carrying capacity of its lifting magnet device may be adjusted to the thickness of the sheets as this carrying capacity is partly to be sufficiently strong for attaching the thickest sheet in the stack, partly so poor that it does not attract two sheets lying on top of each other simultaneously. The abovementioned captivator has two substantial drawbacks. First it is not capable of lifting all sheets, especially not short thick and long thick sheets. Secondly the captivator operates relatively slowly since first it has to pull the sheets up on its conveyor.

SUMMARY OF THE INVENTION The purpose of the invention is to provide a transport apparatus, especially in the form of a gantry crane, which automatically and safely is capable of lifting the topmost sheet of a stack of sheets containing large sheets of various lengths, widths and thicknesses.

The transport apparatus according to the invention is characteristic in that the magnet beam has a series of interspaced magnet beam sections, the sidegoing frame parts of which are situated in the same plane forming an angle to the surface of the sheets in the sheet stack. With the magnet beam sections being thus suspended from an angle in relation to the surface of the sheet stack, is achieved that after the girder with the magnet beam sections has been lowered down on the sheet stack, the topmost sheet of the sheet stack will, during the following hoisting movement of the magnet beam horizontally upwards, first be lifted at its front end by means of the magnets of the first magnet beam section. Not until the first magnet beam section has been lifted up to a certain height, the magnet beam section lying behind will come to lift the topmost sheet, and when the latter magnet beam section has been lifted up to a certain height, the next, behindlying magnet beam section will engage in the lifting of the sheet etc. After the topmost sheet has been lifted up from the sheet stack, the transport apparatus will transport the sheet towards the desired spot, where the sheet will be laid down by a lowering movement of the magnet beam.

Furthermore the transport apparatus according to the present invention is characteristic in that the girder is suspended from the transport apparatus in a substantially horizontal position, and that the magnet beam sections are suspended from the girder by means of wires of various lengths so that the sidegoing frame parts of the magnet beam sections are placed in the same plane forming an angle to the girder. Hereby an oblique suspension of the magnet beam is obtained in a simple manner so that the sidegoing frame parts of the magnet beam sections form an angle to the surface of the sheets of the sheet stack without the girder being turned in advance from a horizontal to an oblique position.

In addition the transport apparatus according to the invention is characteristic in that the girder is suspended from the transport apparatus in a substantially horizontal position and can be turned in relation to this position, and that the magnet beam sections are suspended from the girder by means of wires of the same lengths so that the sidegoing frame parts of the magnet beam sections are placed in the same plane. Hereby it is possible to turn the girder away from its normal horizontal position before the magnet beam is lowered down on the sheet stack so that the sidegoing frame parts of the magnet beam sections form an angle to the surface of the sheet stack; and by turning the girder more or less this angle may be adjusted to a desired value. Furthermore a simple suspension of the magnet beam sections from the girder is obtained by using wires of the same lengths for the suspension.

Moreoever the transport apparatus according to the invention is characteristic in that the electro magnets of the magnet beam sections are magnets of the reversible type (cf. British Pat. No. 1,187,557). The use of such reversible type magnets has the advantage that they can be switched over between two positions, i.e. a first position with the magnets having a maximum carrying capacity, which means that the magnets are capable of carrying a heavy sheet, and another position with the magnets having a small carrying capacity.

Furthermore the transport apparatus according to the present invention is characteristic in that the row of magnet beam sections consists of a front magnet beam section, placed at that end of the girder situated at the greatest distance from the topmost sheet of the sheet stack, and a number of lifting magnet beam sections lying there behind, that the frame of the front magnet beam section is suspended. just as the lifting operation begins. from two carrying wires, one carrying wire being fixed to each side of the center of the frame. that one of the carrying wires has a weight indicator built into it, and that the electro magnets of the front magnet beam section can lift at least half of the actual load. Hereby a rough weighing of that sheet which is in engagement with the front magnet beam section is obtained, since the weight measured by the weight indicator corresponds substantially to a fourth of the weight of the sheet and a fourth of the weight of the magnet beam sections lying behind, as the weight indicator only measures the weight in one side ofthe front magnet beam section and as the top-most sheet with its one end rests on the sheet stack and the lifting magnet beam sections rest on this sheet. while the front magnet beam section lifts the other end of the sheet. In this way. just before the lifting operation is started. a rough indication is obtained as to whether the sheet in engagement with the front magnet beam section is a thin or a thick sheet.

An essential feature of the transport apparatus according to the invention is that each lifting magnet beam section has along its rear frame part an oblong plate magnet which preferably is designed as an oblong reversible-type plate magnet. If, for instance thin sheets are to be lifted, i.e., thin sheets of a thickness of about 3-4 millimetres, an ordinary oblong plate magnet may unintentionally be turned by the underlying sheets because of its large depth effect. If, on the other hand an oblong reversible-type plate magnet is used, made according to the same principle as the round reversibletype magnets described in the previously mentioned British Pat. specification No. 1,187,557, the advantage is achieved that the tractive force of the plate magnet is concentrated upon the top part of the topmost sheet of the sheet stack when the hoisting movement is started. Incidentally, the plate magnet is to be currentcontrolled in such a way that after the hoisting movement having been started, the plate magnet is automatically switched from the position where the tractive force is concentrated upon the topmost sheet to a position where the plate magnet has maximum tractive force.

Another essential feature of the transport apparatus according to the invention is that the magnet in each lifting magnet beam section is pivotally journalled around a horizontal axis, which is parallel to the front or rear frame part. Hereby is achieved that an underlying sheet not to be lifted turns the magnet out of its normal position, such movement can be used for activating the measuring means.

A still further essential feature of the transport apparatus according to the invention is that each lifting magnet beam section is provided with a measuring means so arranged that when the magnet of a lifting magnet beam section during the lifting of the magnet beam is turned an angle in relation to the sidegoing frame part of the lifting magnet beam section, which angle is equal to the angle, which the sidegoing frame parts of the lifting magnet beam sections in their normal suspension position form with the surface of the sheets in the sheet stack, then the measuring means concerned will switch-off the current to the magnet of the lifting magnet beam section concerned, and to all the magnets of the behindlying lifting magnet beam sections. Hereby is achieved that only the front magnet beam sections, the magnet of which is not turned because these magnets are engaged with the topmost sheet, which is lifted up, and because the topmost sheet, which is lifted up, is parallel to the sidegoing frame parts of the magnet beam sections concerned will be supplied with current during the lifting operation, thereby keeping the topmost sheet to be lifted. On the other hand, by means of the measuring means, the current will be switched-off to the magnet of the frontmost of those lifting magnet beam sections, the magnet of which is turned to an angle in relation to the frame of the lifting magnet beam section, which angle is equal to the angle formed by the sidegoing frame parts of the magnet beam section in their normal suspension position to the surface of the sheet stack; and besides the current will be switched-off to all the magnets of the lifting magnet beam sections positioned behind, whereby the switched-off lifting magnet beam sections no longer will engage the underlying sheets during the further lifting of the magnet beam.

In addition, an essential feature of the transport apparatus according to the invention is that the measuring means is a microswitch attached on the rear frame part magnet positioned behind the rear edge of the sheet to be lifted, and which besides can switch-off the current to all the magnets of the lifting magnet beam sections positioned behind the first mentioned magnet.

Furthermore, an essential feature of the transport apparatus according to the invention is that the magnet beam sections are inter-connected by means of movable, mechanical coupling links. Hereby is obtained that the individual magnet beam sections are capable of performing the requisite movement mutually during the lifting of a sheet.

Moreover, an essential feature of the transport apparatus according to the invention is that each coupling link consists of hinge plates attached on opposite frame parts of adjacent magnet beam sections, and of hinge pins extending transversely through eyes in the hinge plates. Hereby is achieved a simple and robust coupling link rendering turning between two adjacent magnet beam sections possible.

BRIEF DESCRIPTION OF THE DRAWING The invention is further explained below with reference to the drawings in which, I

FIG. 1 shows in perspective an embodiment of a transport apparatus according to the invention in the form of a gantry crane with a magnet beam suspended in an oblique plane and consisting of a number of magnet beam sections, the coupling links between the sections being deleted for sake of clarity, I

FIG. 2 on a larger scale and viewed from above the front magnet beam section and a fragment of the magnet beam section lying behind according to FIG. 6, the front magnet beam section being imaginably lowered down on the sheet stack,

FIG. 3 diagrammaticly on a smaller scale and viewed from the side the transport apparatus in FIG. l,

FIG. 4 diagrammaticly on a smaller scale and viewed from the side another embodiment of the transport apparatus in FIG. 1, the magnet beam being situated in a horizontal position,

FIG. 5 the same, the magnet beam being turned an angle,

FIG. 6 diagrammaticly on a larger scale and viewed from the side a fragment of an amended embodiment of the magnet beam shown in FIG. 1 at an initial stage of the hoisting movement of the magnet beam, the front magnet beam section of the magnet beam lifting up a short sheet,

FIG. 7 the magnet beam shown in FIG. 6 at a later moment when the sheet is lifted free of the sheet stack,

FIG. 8 the magnet beam shown in FIG. 6 during the lifting of a longer sheet and FIG. 9 the magnet beam shown in FIG. 6 during the lifting of a long sheet.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a transport apparatus in the form of a gantry crane consisting of two portals 57 and 58, a girder 59, combining the two portals, and a magnet beam 60, the girder 62 of which is suspended from the girder 59 by means of wires 61. The portals 57 and 58 have at the foot travelling wheels (not shown), which, in relation to the longitudinal direction of the girder 62, can run on longitudinal or athwart rails (not shown). The gantry crane has run over a sheet stack 73, consisting of a number of steel sheets, the lengths, widths and thicknesses of which may vary. The magnet beam 60 consists of a traverse or girder 62 and a series of interspaced magnet beam sections 63, 64, 65, 66, 67, 68, 69, and 70, which by means of wires 97 are suspended from the girder 62.

As shown in FIG. 2 each magnet beam section 63, 64 has a frame 1 which consists of a front transverse frame part 2, a rear transverse frame part 3 and two sidegoing frame parts 4 and 5, which frame parts 2-5 can e.g. be U-shaped sectional irons.

In the embodiment of the transport apparatus shown in FIGS. 1 and 3 the wires 97 of the magnet beam sections 63 70 are of various lengths, so that the sidegoing frame parts 4, 5 of the magnet beam sections are placed in the same plane forming an angle 7 with the girder 62 said girder 62 being suspended from the girder 59 of the gantry crane in a substantially horizontal position. Since the girder 62 is parallel to the sheet stack 73. said angle is equal to the suspension angle beta. i.e.. the angle which is formed by the side-going frame parts 4, 5 of the magnet beam sections 63-70 in their suspension position to the surface of the sheets in the sheet stack 73. By using wires 97 of various lengths as shown in FIG. 1 an oblique suspension of the magnet beam sections 63-70 is obtained without it being necessary to turn the girder 62.

In FIG. 4 another embodiment of the transport apparatus is shown which, e.g., as shown may be formed as a gantry crane. The girder 62 is suspended from the girder 59 of the gantry crane and is in FIG. 4 in a horizontal position. In contradiction to the girder 62, shown in FIG. 1, the girder 62 in FIG. 4 may turn in relation to its horizontal position, one end of the girder 62 is lifted or lowered in relation to the other end. This lifting or lowering can, e.g., be carried out by two hoisting machineries (not shown), which are mounted on the girder 59 andwhich can operate independently. The magnet beam sections 63-70 are suspended from the girder 62 by means of wires 97 of the same length, so that the side-going frame parts 4 of the magnet beam sections 63-70 are in the same plane.

In order that the side-going frame parts 4, 5 of the magnet beam sections 63-70 may form an angle ,8 with the surface of the sheets in the sheet stack 73, the girder 62 is turned from its normal non-operative position to the turned working-position shown in FIG. 5 by means of the hoisting machineries. Hereafter the girder 62 is lowered down on the surface of the sheet stack 73 and lifting of the topmost sheet can be started.

By the embodiment shown in FIGS. 4 and 5 it is obtained that the angle )3 which the side-going frame parts 4, 5 of the magnet beam sections form with the surface of the sheet stack 73, can be adjusted to a desired value. The suspension angle B may thus be varied in contradiction to the embodiment in FIG. 3 where the suspension angle 5 has a fixed value. By using wires 97 of the same length as shown in the embodiment according to FIGS. 4 and 5 a very simple suspension of the magnet beam sections 63-70 from the girder 62 is obtained.

The series of magnet beam sections 63-70 consists of a front magnet beam section 63 and a number of lifting magnet beam sections 64-70 lying behind. The front magnet beam section 63 is placed at the end of the girder 62 situated at the greatest distance from the topmost sheet 78 in the sheet stack 73.

The individual magnet beam sections 6370 have expediently a width, which is smaller than the width of the narrowst sheet in the sheet stack 73.

In FIG. 6 a fragment of the magnet beam 60 of FIG. 1 is shown diagrammaticly, viewed from the side during the lifting of a short sheet 78.

The magnet beam section 63 shown in FIG. 1, 2 and 6 has an oblong plate-magnet 15 at its front end and an oblong plate-magnet 21 at its rear end. The platemagnets 15 and 21 can, e.g., each be replaced by one series of circular magnets of the reversible type as described in the previously mentioned British Pat. specification No. 1,187,557, e.g., three magnets in each series. The rearmost magnet 21 is pivotally journalled around a horizontal axis 114 going through the center point of the topside of the magnet 21. Between the magnets 15 and 21 one or several circular or oblong magnets may be mounted so that the electro magnets of the front magnet beam section 63 can lift at least half of the actual load, i.e., the heaviest sheet which is to be lifted by the transport apparatus, and half of the lifting magnet beam sections lying behind.

Each of the lifting magnet beam sections 64, 65, can along each rear frame part have a series of circular magnets 81 (FIG. 1). e.g.. of the reversible type. or as shown in the amended embodiment in FIG. 6 an oblong plate magnet 100. This oblong plate magnet 100 is expediently designed as an oblong plate-magnet of the reversible type. The use or this type of magnets has the advantage that said magnets can be switched over between two positions,

i.e., a first position with the magnets having a maximum carrying capacity, which means that the magnets are capable of carrying a heavy sheet, and another position with the magnets having a reduced carrying capacity so that the transport apparatus is capable of lifting thin sheets.

If, e.g., thin sheets are to be lifted, i.e., thin sheets of a thickness of about 3-4 mm an ordinary oblong platemagnet 100 may unintentionally be turned by the underlying sheets because of its large depth effect. If, on the other hand, an oblong plate-magnet 100 of the reversible type is used, said magnets being made according to the same principle as the circular magnets described in the previously mentioned British Pat. specification No. 1,187,557, the advantage is achieved that the tractive force of the plate-magnets is concentrated upon the top part of the topmost sheet of the sheet stack, when the hoisting movement is started. Incidentally, the plate magnet is to be current-controlled in such a way that after the hoisting movements having been started the plate-magnet is automatically switched from the position where the tractive force is concentrated upon the topmost sheet to a position where the plate-magnet has maximum tractive force.

As it appears from FIGS. 2 and 6 the frame 1 of the front magnet beam section 63 is suspended from two carrying wires 95, one carrying wire being fixed to each side of the centre of the frame 1. At a suitable spot a weight indicator 38 (cf. FIG. 2) is built into one of the carrying wires 95. By means of such a weight indicator 38 a rough weighing of the sheets is obtained with which the front magnet beam section 63 is in engagement. This is possible, since the weight measured by the weight indicator corresponds substantially to a fourth of the weight of the sheet and a fourth of the weight of the magnet beam sections lying behind, as the weight indicator only measures the weight in one side of the front magnet beam section 63 and as the topmost sheet with its one end rests on the sheet stack 73 and the lifting magnet beam sections 64-70 rest on this stack. while the front magnet beam section 63 lifts the other end of the sheet. In this way just before the lifting operation is started a rough indication is obtained whether the sheet, with which the front magnet beam section is in engagement, is a thin or a thick sheet.

Each of the oblong plate-magnets 100 in the embodiment according to FIG. 6 is pivotally joumalled around a horizontal axis 83 which is parallel to the front or rear frame part 2 respectively 3 (FIG. 2). Hereby it is obtained that an underlying sheet not to be lifted turns the magnet 100 out of its normal position in relation to the side-going frame part 4, said movement can be used for activating a measuring means 84 mentioned below.

The oblong magnets and 21 in the front magnet beam section 63 is pivotally joumalled around end journals 113 respectively 114 (FIGS. 2 and 6) mounted in holes in the side-going frame parts 4 and 5. Each lifting magnet beam section, for instance 64, has a measuring means, especially a micro-switch 84 (FIG. 6), so arranged that when the magnets 100 during the lifting of the magnet beam section 63 are turned an angle in relation to the sidegoing frame parts 4 of the lifting magnet beam section 64, which angle is equal to the suspension angle of the lifting magnet beam sections in the girder 62, then the micro-switch 84 will switch off the current to the magnets 100 in the lifting magnet beam section 64 and to all the magnets 100 in the lifting magnet beam sections 65,66, 70 lying behind. Hereby is achieved that only the front lifting magnet beam sections or the front lifting magnet beam section 64 (in FIG. 9), the magnets 100 of which are not turned because these magnets 100 are engaged with the topmost sheet 78, which is being lifted up, and because the topmost sheet 78" is parallel to the sidegoing frame part 4 of the lifting magnet beam sections or the lifting magnet beam section 64 concernedwill be supplied with current during the lifting operation, thereby holding the topmost sheet 78 to be lifted. On the other hand, the current will be means of the micro-switch 84 designed as a measuring means be switched-off to the magnets 100 of that lifting magnet beam section 65, the magnet 100 of which is turned an angle in relation to the sidegoing frame part of the lifting magnet beam section. which angle is equal to the suspension angle of the magnet beam section in the girder 62; and besides the current will be switched-off to all the magnets 100 in the lifting magnet beam sections 66,67, 70 lying behind, whereby the currentless lifting magnet beam section 65 no longer will seize the underlying sheets during the lifting of the magnet beam 62.

The micro-switch 84 is placed on the rear frame part of each lifting magnet beam section and activated by a spring 85 (FIG. 6) connected with the magnet 100. Hereby is achieved in a simple and reliable way an activation of the micro-switch 84 when the magnet 100 is turned. Instead ofa micro-switch, for instance a photoelectric cell or an inductive feeler or a potentiometer which produce a voltage proportional to the angular motion of the magnets can be used as a measuring means.

The magnet beam sections 63,64, are interconnected by means of movable, mechanical coupling links 99 as shown in FIGS. 2 and 6. Hereby is ensured that the individual magnet beam sections 63,64, 70, during the lifting of a sheet, can perform the mutual movements required. Each coupling link 99 consists preferably of two hinge plates 101 and 102, positioned on opposite frame parts 2 and 3 of adjacent magnet beam sections, such as for instance 63 and 64 in FIG. -6, and one hinge pin 1 03 extending through eyes in the hinge plates 101 and 102. The coupling link 99 renders a robust and simple coupling link possible ensuring that turning can take place between two adjacent magnet beam sections.

The carrying wires (FIG. 6) of the front magnet beam section 63 are at their top ends connected with a pressure spring 96, placed in the girder 62. The wires 97 from which the magnet beam sections 63-70 are suspended are at their top ends connected with a pressure spring 98 mounted on the girder 62. By giving these springs 96 and 98 a suitable pre-stressing, it is possible to regulate the length of the individual wires 95 and 97so that the sidegoing frame part 4 of the individual magnet beam sections come in the same oblique level, and so that the underside of the frame part 4 is on the same level. Thus it is possible to allow for inaccuracies arising from ordinary wear and tear during the use and, from the manufacture of the individual magnet beam sections or-inaccurate suspension during the mounting of the magnet beam sections. An accurate suspension ensures that the individual magnet beam sections participating in the lifting of the topmost sheet 78 or 78' or 78", essentially come to carry the same weight.

LIFTING OF A SHORT SHEET ACCORDING TO FIGS. 6 AND 7 Automatic lifting of a short sheet 78, the length of which is equal to about the length of a magnet beam section, is done in the following way. The girder 62 with the magnet beam sections 63,64,65, 70 is lowered down on the sheet stack 73. Full voltage is switched-on to all the magnets 15,21 and of the magnet beam sections. Then the girder 62 starts the hoisting movement. After a certain hoisting movement of the girder 62, the magnet beam takes up the position shown in FIG. 6. The front magnet beam section 63 is turned and lifted forming an angle, which is equal to the suspension angle B. By a further hoisting movement not only the front magnet beam section 63 will be lifted, but also the front lifting magnet beam section will be lifted at its front end because of the coupling link 99 "1511566556of"; continuous hoisting movement the oblong plate magnet 100, engaged with the topmost sheet but one 77, will be turned in relation to the lifting magnet beam section 64. In FIG. 7 the magnet beam is lifted so much that the oblong plate magnet 100 of the lifting magnet beam section 64 has turned an angle which is equal to the suspension angle beta. Thereby the micro-switch 84 is activated by the spring 85, whereby the current to the oblong plate magnet 100 is switched-off and to the behindlying plate magnets 100 in the lifting magnet beam section 65,66, 70. Through the further hoisting movement the lifting magnet beam sections 65,66, 70 are lifted in succession up from the sheet stack 73. When all the lifting magnet beam sections 64-70 have been lifted up from the sheet stack 73, the gantry crane transports the sheet 78 to the desired location where the sheet 78 is laid down by a lowering movement of the girder 62.

LIFTING OF A LONGER SHEET ACCORDING TO FIG. 8.

The automatic lifting of a longer sheet 78 (FIG. 8), i.e., a sheet, the length of which is one and a half times the length of a magnet beam section, proceeds in the same way as described above in connection with the lifting of the short sheet 78 in FIGS. 6 and 7. The position of the magnet beam shown in FIG. 8 corresponds to the position shown in FIG. 7.

LIFTING OF A LONG SHEET ACCORDING TO FIG. 9

With reference to FIG. 9 showing the lifting of a long sheet 78 all the oblong plate magnets 100 are switched-on as thin plate magnets during the initial stage of the lifting of the topmost sheet 78". If the micro-switch 84 of the lifting magnet beam section 64 is not activated, when the lifting magnet beam section 64 is lifted up clear of the sheet stack 73, full current intensity is switched-on to the oblong plate magnet 100 in the lifting magnet beam section 64.

The weight indicator 38 serves as mentioned above to ascertain whether a thin or a thick sheet is placed under the magnet beam. Hereby the weight indicator 38 ensures that the used magnets 15,21, 100 of the reversible type are switched-on to either the thin plate function or the thick plate function, i.e., that the magnets function either as thin plate magnets or as thick plate'magnets (strong magnets). First the case is considered where a thin sheet is placed under the magnet beam. When the weight indicator 38 has indicated that a thin sheet is concerned, all the magnets 15,21,100 are switched-on as thin plate magnets. Thereafter the depth of the magnetic field is not greater than the thickness of the thin sheet. By lifting the magnet beam is hereby avoided that the magnet picks up more than the topmost sheet. When the magnet beam has been moved a few centimetres up above the surface of the sheet stack 73, the magnets 15,21,100 are switched-on to thick plate function for purposes of security.

Thereafter the case is considered where a thick sheet is placed on top of the sheet stack 73. When the weight indicator 38 has ascertained that a heavy sheet, and consequently a thick sheet is concerned, the magnets 15,21,100 are switched-on to thick plate function. Hereby is avoided that the magnet beam will lift two or more sheets because the magnetic field does not extend beneath the underside of the thick sheet.

The gantry crane according to the invention with the oblique suspended magnet beam sections renders it possible to lift one sheet at a time from a buffer stack in which steel sheets of arbitrarily large length have been stacked. Such sheet stacks are for instance found in sheet stores at shipbuilding yards.

A characteristic of the lifting operation of the magnet beam is that a sheet, when lifted, is first lifted up by its front edge.

Since a sheet lifted up by means of the magnets invariably will flush with the longitudinal frame parts of the magnet beam sections, this sheet cannot cut-out (switch-off the current to) the magnets which are to remain switched-on as the switch-off of the current to the magnets only will happen when a magnet takes up a position in which this is turned an angle equal to the suspension angle ['1 in relation to the frame of the magnet beam section concerned. The turned position of the magnet is characteristic of the process of lifting of a sheet. The turned position will only occur when an underlying sheet, not to be lifted, turns the magnet out of its normal position, whereby the micro-switch belonging to the magnet is activated and the magnet current switched-off.

The present invention is not limited to the embodiments shown and described but can be modified in many ways within the scope of the succeeding claims.

I claim:

1. A transport apparatus, especially a gantry crane, provided with a magnet beam for lifting and transporting sheets of magnetizable material, especially steel sheets,from a stack of sheets which magnet beam has a girder and a series of spaced beam sections suspended from the girder by means of wires, each beam section having a frame with a front and a rear transverse frame part and two sidegoing frame parts and one or more electro magnets mounted in the frame, the sidegoing frame parts of each of the beam sections being situated in the same plane forming an angle ([3) to the surface of the sheets in the sheet stack.

2. A transport apparatus according to claim 1, characterized in that the girder is suspended from the transport apparatus in a substantially horizontal position, and that the magnet beam sections are suspended from the girder by means of wires of various lengths so that the sidegoing frame parts of the magnet beam sections are placed in the same plane forming an angle (y) to the girder.

3. A transport apparatus according to claim 1, characterized in that the girder is suspended from the transport apparatus in a substantially horizontal position and can be inclined relative to this position, and that the magnet beam sections are suspended from the girder by means of wires of the same lengths so that the sidegoing frame parts of the magnet beam sections are placed in the same plane.

4. A transport apparatus according to claim 1 characterized in that the electro magnets of the magnet beam sections are magnets of the reversible type.

5. A transport apparatus according to claim 4, characterized in that the series of magnet beam sections consists of a front magnet beam section, placed at the end of the girder situated at the greatest distance from the topmost sheet of the sheet stack and a number of behind lying lifting magnet beam sections, that the frame of the front magnet beam section is suspended from two carrying wires, one carrying wire being fixed to each side of the centre of the frame, that one of the carrying wires has a weight indicator built into it, and that the electro magnets of the front magnet beam section can lift at least half of the actual load. 7

6. A transport apparatus according to claim 5, characterized in that each lifting magnet beam section has along its rear frame part an oblong plate magnet.

7. A transport apparatus according to claim 6, characterized in that the plate magnet is designed as an oblong reversible-type plate magnet.

8. A transport apparatus according to claim 4, characterized in that the magnet in each lifting magnet beam section is pivotally journalled around a horizontal axis, which is parallel to thefront or rear frame part.

9. A transport apparatus according to claim 4 characterized in that each lifting magnet beam section is provided with a measuring means so arranged that when the magnet of a lifting magnet beam section during the lifting of the magnet beam is turned an angle in relation to the sidegoing frame part of the lifting magnet beam section, which angle is equal to the angle, which the sidegoing frame parts of the lifting magnet beam sections in their normal suspension position form with the surface of the sheets in the sheet stack, then the measuring means concerned will switch-off the current to the magnet of the lifting magnet beam section concerned, and to all the magnets of the behindlying lifting magnet beam sections.

10. A transport apparatus according to Claim 9, characterized in that the measuring means is a microswitch attached on the rear frame part of each lifting magnet beam section, and which can be activated by a spring connected with the magnet at the rear frame part of the lifting magnet beam section.

11. A transport apparatus according to claim 1, characterized in that the magnet beam sections are interconnected by means of movable, mechanical coupling links.

12. A transport apparatus according to claim 11, characterized in that each coupling link consists of hinge plates attached on opposite frame parts of adjacent magnet beam sections, and of hinge pins extending transversely through eyes in the hinge plates.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2565927 *Jun 28, 1947Aug 28, 1951Morgan Construction CoApparatus for handling annular articles
US3486784 *Oct 18, 1967Dec 30, 1969Nielsen & Son Maskinfab As HMagnet lifting yoke
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4077507 *Dec 11, 1975Mar 7, 1978Bertin & CieMetal sheet conveyor with linear electric motor and ground-effect shoe
US4136789 *Mar 15, 1977Jan 30, 1979B.V. Koninklijke Maatschappij "De Schelde"Conveying, storage and sorting system for large metal sheets, particularly for use in shipbuilding
US5151006 *Jun 20, 1989Sep 29, 1992Outokumpu OyAutomatic charging member
US6394519Nov 10, 1999May 28, 2002R&D Engineering & Macining, Inc.Adjustable pick-and-place tool for an automated robotic device or the like
Classifications
U.S. Classification414/797.1, 414/618, 294/65.5, 414/626
International ClassificationB66C1/06, B66C1/00, B65H3/00, B65H3/16
Cooperative ClassificationB66C1/06
European ClassificationB66C1/06
Legal Events
DateCodeEventDescription
May 26, 1981AS02Assignment of assignor's interest
Owner name: H. NIELSEN & SON MASKINFABRIK A/S
Effective date: 19810305
Owner name: MAGNEMAG HAGOU A/S, METERBUEN 6-12, DK-2740 SKOVLU
May 26, 1981ASAssignment
Owner name: MAGNEMAG HAGOU A/S, METERBUEN 6-12, DK-2740 SKOVLU
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:H. NIELSEN & SON MASKINFABRIK A/S;REEL/FRAME:003854/0872
Effective date: 19810305
Owner name: MAGNEMAG HAGOU A/S,, STATELESS
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:H. NIELSEN & SON MASKINFABRIK A/S;REEL/FRAME:003854/0872