US2855197A

US2855197A - Magnetic sheet handler

Info

Publication number: US2855197A
Application number: US567990A
Authority: US
Inventors: Leonard W Nash
Original assignee: L W NASH CO
Current assignee: L W NASH CO
Priority date: 1956-02-27
Filing date: 1956-02-27
Publication date: 1958-10-07
Anticipated expiration: 1975-10-07

Description

Oct. 7, 1958 I L. V\ I NA S H 2,855,197

MAGNETIC SHEET HANDLER Filed Feb. 27, 1956 s Shets-Sheet 1 JNVENTOR. Leonard m Nash mg ATTORNEYS Oct. 7, 1958 L. w. NASH 2,855,197

MAGNETIC SHEET HANDLER Filed Feb. 27. 1956 5 Sheets-Sheet 3 86 I r I I 86 i6 II I" I PM a r, 84 M A A 'S-l #84 90 P l I 90 Ls-4 I I06 5o-' [lulu 50 LLs-s la -||2 INVENTOR. Leonard M. Nash HIS ATTORNEYS Oct. 7, 1958 Filed Feb. 27, 1956 L. W. NASH MAGNETIC SHEET HANDLER 5 Sheets-Sheet 4 IN V EN TOR.

L eonard m Nash BY g WW8 ATTORNE Y5 Oct. 7, 1958 w. NASH MAGNETIC SHEET HANDLER 5 Sheets-Sheet 5 Filed Feb. 27, 1956 INVENTOR. Leonard Ml Nash TwS BY W 7n I HAS A r romvs rs United States Patent 2,855,197 MAGNETIC SHEET HANDLER Leonard W. Nash, Columbiana, Ohio, assignor to L. W. Nash Company, East Palestine, Ohio Application February 27, 1956, Serial No. 567,990 18 Claims. (Cl. 271-18) This invention relates to a magnetic sheet handler for feeding individual metal sheets to conveying or processing machinery. More particularly, the magnetic sheet handler of the invention receives stacks of metal plates or other magnetizable sheets and individually operates on each stack to remove the sheets therefrom, one at a time, from the top to the bottom of the stack. The successive stacks of sheets may continually vary in height with one another through a considerable range of sizes and the destacking operation is uniformly effective in the handler for each size of stack, although the low stacks are, of course, destacked in proportionately less time than the larger stacks. I

In many sheet metal pickling, de-scaling, rolling, crimping, and other operations it is customary to receive the sheet metal in stacks or bales by reason of the convenience in handling and transferring the metal sheets in compact and orderly arrangements, rather than individually or loosely in the aggregate. Such operations as the foregoing usually proceed with a treatment of each sheet at both sides simultaneously or at least in a sepa rated relationship to the other sheets, and therefore require that the sheet metal be destacked prior to operating upon or treating the sheets. This individual separation or destacking of the sheets is accomplished in the present sheet handler through provision of a power lift platform on which a stack of sheets is supported, and a cooperating frame of depending magnets toward which the lift platform progressively rises to transfer the sheets in succession off the top of the stack into the field of influence of the magnets. One important feature of this sheet handling machine is the provision of a set of conveyor rollers in the machine frame to which the sheets cling under the magnetic suspending force and along which the suspended sheets are conveyed as they are individually fed from the machine.

A primary object of the present invention is to provide, in a machine such as the foregoing, a system of switching elements and mechanism controlled thereby which senses the progress of the stack and sheets in the machine at various stages and renders the destacking and feeding operations essentially automatic. More particularly, the machine embodies several beds and platforms of conveyor rollers, and I provide switches in these beds at strategic points which, in conjunction with the operation of a photoelectric cell switch, enable the sheets to operate the switches and control the machine in rapid, trouble-free cycles of operation.

In the accompanying drawings illustrating a preferred embodiment of my invention:

Figure l is a plan view of the magnetic sheet handler machine,

Figure 2 is a sectional view in elevation taken to en larged scale along the lines II-II of Figure 1 and showing the magnet frame section and the confronting lift platform section therebelow.

Figures 3 and 4 are longitudinal sectional views taken it. to enlarged scale along the lines of Figure 1,

Figure 5 is a diagrammatic view of the hydraulic circuit controlling the lift platform section and,

Figure 6 is a wiring diagram of the automatic controls for the mechanism for the machine including the hydraulic circuit and the magnets.

In particular reference to Figures 14, a magnetic sheet handler machine is shown having an entrance table 10, a transfer roller bed 12, and an upright framework 14 incorporating a magnet and roller section 16 and a lift platform section 18. The magnet and roller section 16 is adapted to deliver individual metal plates from a stack S to a conveyor 20 which is diagrammatically shown and which either directly or indirectly transfers the sheets to processing machinery 22 (Figure 2).

More particularly, the entrance table includes a base 24 which carries a series of slightly downwardly sloping roller frames 26 each having a bed of freely rotatable conveyor rolls 28. The frames 26 are spaced laterally from one another in accordance with Figure 1 to accommodate sets of lifting fork arms, not shown, employed to deposit a stack of metal sheets S thereon, Figure 3. The transfer roller bed 12 is horizontally disposed and includes a base 30 which supports two sets of rollers 32 arranged side by side. An electric motor 34 drives the rollers 32 through a common cross shaft 36 appropriately connected to a gear type speed reducer 38. A chain and sprocket drive 40 provided for each set of rollers 32 coordinates their motion of rotation. The transfer roller bed 12 has a shaft 42 which extends across the full width thereof and which carries an operating handle 44 at one end. Intermediate its ends, the shaft 42 carries a plurality of fixed levers 46 each of which is spaced from the others and carries an individual stop pin 48 which protrudes from a guide to a point above the level of the conveyor rollers 32. Rotation of the shaft 42 in a clockwise direction as viewed in Figure 3 causes the levers 46 to assume a dotted line position 460 in which the normally protruding upper ends of the pins 48 are caused to be retracted in their guides below the level of the rollers 32.

The upright framework 14 is rectangular in shape and has an inverted U shaped frame at each side thereof consisting of a pair of inner and outer columns 50 of I-beam construction which are connected at their upper ends by means of an angle member 52 and a channel member 54, Figure 2. A base plate 56 interconnects the lower ends of the pair of columns 50 in each U frame and is suitably anchored to supporting masonry or to a concrete bed 57. The base plate 56 carries a set of leveling screws 58. A pair of spaced cross beams 60 of channel shaped construction form bridging members between the U frames, extending between the sides of the machine and being welded at their corresponding ends to the channel member 54 at that sidev A series of short hanger bars 62 is welded to the upper edges of the cross beams 60 and each hanger bar 62 carries a U-shaped core 63 provided with an electrical coil 64 on each of the salient poles 66 thereof. Below each coil 64, the salient pole carries a pair of spaced roller wheels 68. A series of driven conveyor rollers 70 is arranged in alternation with the pairs of roller wheels 68 which may also be power driven but as shown are freely rotatable idler rollers and together the live and

idler roller

68, 70 cooperate to define a common horizontal plane for conveying sheets of metal thereal'ong. A driven pair of mutually opposed upper and lower pinch rolls is diagrammatically indicated at 72, Figure 2, in alignment with the plane of the underside of these rollers. These IIIIII and IV'IV rolls 72 keep the leading edge of the moving sheet in line with the conveyor 28 to which the sheets are fed regardless of whether the magnetic suspending force from the coils 64 thereafter partially or completely collapses. The cross beams carry a series of bearing brackets 74 on their underside which journal the stub shafts 75 on which the conveyor rollers 70 are mounted. A chain and sprocket drive '76 interconnects the conveyor rollers 70 for coordinated driving movement together in the direction of the arrow 77, Figure l. A continually running motor 78, Figure l, is connected to the chain and sprocket drive 76 by means of a mechanical speed reducer 80 and an intervening chain and sprocket connection 82.

At each of the four corners of the rectangular upright framework 14, the columns 50 carry a bracket 84 which, rigidly supports a hydraulic lifting cylinder 86. Each of the hydraulic lifting cylinders 86 has a vertically sliding piston 88 which divides the cylinder into lower and upper working chambers as viewed in Figure 4. A piston rod 90 extends through the lower working chamber and is connected at its upper end to the piston 88 and at its lower end the piston rod 90 carries a elevis and a pivot pin 92. The lift platform 18 is of rectangular shape and rigidly mounts an apertured lifting lug 94 at each corner thereof which receives the adjacent pivot 92 so as to connect the platform 18 and each of the piston rods 90. The outer ones of the columns 50 carry a pair of vertically disposed racks 96 adjacent the ends of the platform 18. A stabilizer bar 98 is journaled at spaced points in a set of bearings 1.80 carried by the platform 18 and a pinion 102 affixed to each end of the bar 98 meshes with the stationary rack 96 at that end. The bar 98 interconnects the platform 18 and the stationary racks 96 in known manner and torsionally resists any tendency toward movement of the platform 18 out of its normally horizontal position, for instance, tilting movement due to unequal pulling of the piston rods 90 attended by unequal rotation of the pinions 102 on the racks. The platform 18 has a plurality of parallel mounting brackets 104 on the upper surface thereof which carry a series of four sets of freely rotatable conveyor rollers 106; a stop 108 is suitably provided at one end of each pair of roller sets 106. The rectangular lift platform 18 which may be readily constructed from a box of frame members such as channel beams 110, Figure 3, is movable upwardly and downwardly by the cylinders 86 from a remote position in which they engage a stationary set of lower stops 112 into an upper position closely confronting the magnet and roller frame 16.

In Figure 5, a hydraulic pump 114 has an intake line 116 connected to a hydraulic reservoir 118 and supplies hydraulic fluid in a pump delivery line 120 which is connected to a solenoid operated three-spool valve 122 for controlling the lift platform 18. The pump delivery line 120 has a branch passage 124 which is connected to the lower chambers in the hydraulic cylinders 86 through a conventional flow check valve 126 and a header 128. The three-spool valve 122 has a pair of vent lines 130 connected to the reservoir 118 through a drain line 132. A down relay coil DR and a coil spring 134 cooperate in shifting the valve 122 between its neutral solid line position and its dotted line operating position 122a in Figure 5, and an up relay coil UR and a coil spring 136 cooperate in shifting the valve 122 between its solid line neutral position aforesaid and an opposite operating position shown by the dotted lines 1221) in Figure 5. When the DR and UR coils are unenergized, the

coil springs

134 and 136 tend to balance one another and hold the spools of the valve 122 and the upper chambers in the cylinders 86 through a conventional flow check valve 138 and a header 140. The flow check valves 126, 138 operate in well-known fashion to unseat and freely supply hydraulic fluid to their

respective headers

128, 140, but to restrict the flow of vented fluid escaping from the headers and returning to drain. A by-pass connection per 142 by-passes the flow-check valve 138 and contains a solenoid valve 144 controlled by a return spring 146 and a by-pass relay BR.

Energization in the down relay DR in Figure 5 causes the valve 122 to shift into the operating position 122a to pressurize the line 137 at line pressure and direct hydraulic fluid through the freely operating flow-check valve 138 and header into the upper chambers in the cylinders 86. Simultaneously, owing to the fact that both vents 130 are blocked by the valve spools, line pressure is introduced through the branch line 124 into the lower chambers in the cylinders 86. By the well-known action of a differential motor, equal pressures in the upper and lower chambers effective on the respective different sized areas on opposite sides of the pistons 88 cause the pistons to move the platform 18 downwardly and at a rate controlled by the restricted escape of hydraulic fluid back through the flow-check valve 126 which resists flow in that direction.

Energization of the up relay UR causes the valve 122 to shift into the operating position shown by the dotted lines 12% in which the line 124 is supplied under line pressure to pressurize the lower working chambers in the cylinders 86. Simultaneously the line 137 from the upchambers is connected in a path to the drain 132 through the appropriate one of the vents 130 and hydraulic fluid thus escapes through the flow-check valve 138 which resists the flow in that path. The pistons 88, therefore, cause upward movement of the lift platform 18. Normally, the by-pass relay coil BR is energized during initial upward movement of the platform 18 thereby by-passing the flow check valve 138 by means of the solenoid valve 144 and causing a fast initial rate of lift of the platform 18. This fast rate of lift continues under these circumstances until the by-pass relay BR becomes deenergized whereupon the flow-check valve 138 is effective to restrict the rate of upward movement of the lift platform 18 to a slow feed speed.

By way of a brief reference again to Figures 2, 3 and 4 of the drawings, a pressure type limit switch LS1 is included in the bed of rollers 32 in the transfer roller bed 12 and has an upwardly protruding actuating finger sensitive to the presence of sheets thereabove. A similar pressure type limit switch LS2 is included in the bed of rollers of the magnet and roller frame 16 so as to be sensitive to the presence of metal sheets thereupon. A pressure switch LS-3 having two sets of contacts is mounted to one of the stops 112, Figure 4, to sense the presence of the lift platform 18 in its lowermost or most remote position relative to the magnet and roller frame 16. A pressure type limit switch LS-4 having four sets of contacts is included in the lift platform roller bed so as to be sensitive to the presence of a stack or a single sheet of metal on the lift platform rollers 106. A photoelectric cell switch PEC is arranged at one side of the vertical framework 14 and a light source 147 is arranged at the opposite side and focused in direct line of sight therewith.

An electrical wiring diagram is shown in Figure 6 which includes the limit switches LS1, LS-Z, LS-3 and LS-4 and the PEG switch just described. In Figure 6, a pair of

power supply conductors

148, 150 has a circuit 152 included therebetween having a manual starting switch MS1 to bring the magnet sheet feeder into operation. The switch MS-l operates an electromagnetic relay switch 154 having three sets of upper operating contacts, a, b, and c and a lower set of contacts d, forming a holding circuit. The three sets of upper contacts connect the transfer roller bed motor 34 and an A. C. source of power, not shown, to drive the roller bed rollers 32 in synchronism. The circuit 152 has a branch which includes the limit switch LS-1 located in the transfer roller bed 12 to insure that any stack of sheet metal occupying the same will be advanced by the motor 34 until it reaches the edge of the transfer roller bed 12. In another branch connected in the circuit 152 in parallel to the switch LS-l, a set of normally open contacts LS3a and a set of normally closed contacts LS4a are connected in the series to one another. The contacts LS-3a are included in the limit switch LS3, Figure 3, and the contacts LS4a are included in the pressure switch LS4 in the bed of the lift platform 18. A manual switch MS-2 is included in a branch of another circuit 156 so as to be electrically in parallel with another set of series connected contacts LS-3b and LS4b both normally closed. The circuit 156 further includes the down relay coil DR and also the coil for an electromagnetic switch 158 providing a magnetic interlock between the circuit 156 and another circuit 160. The circuit 160 includes the normally closed switch LS-2 and a normally open set of contacts LS4c in the switch LS4. The circuit 160 further includes an upper branch containing the up relay coil UR and a lower branch including the by-pass relay coil BR in series with an upper set of contacts a in the electromagnetic switch 162. The electromagnetic switch 162 is included in a circuit 164 in series with the PEG switch Whose photoelectric cell component is sensitive to light normally shining thereon from the light source 147 already noted. When a light beam focuses on the PEG switch, it closes and energizes the switch 162 to close its upper set of contacts a. When the light beam is blocked by a rising stack of sheets, the PEG switch opens to deenergize the switch 162 which opens the upper set of contacts a and closes a lower set of contacts b. The lower set of contacts [7 in the electromagnetic switch 162 closes a circuit 166 which energizes the paired electromagnetic coils 64 in the magnet and roller frame 16. A trim rheostat 168 is included in circuit with the coils 64 to adjust the intensity of the strong magnetic field which they create. Additionally included in circuit with the coils 64 is a normally open set of contacts LS-4a' in the lift platform limit switch LS4 and also a timer switch 170. In one physically constructed embodiment of the invention, the timer switch 170 was arranged to be operated in repetitive six-second cycles in which it is held open for seconds and closed for only 1 second, thereby to energize the cells 64 in submultiple spaced periods of 1 seconds duration.

In operation of the magnetitc sheet handling machine of the preceding figures, an operator moves the handle 44, Figure 3, to lower the stop pins 48 and permit a loaded stack of sheets S to roll by gravity from the sloping entrance table 10 onto the horizontal transfer roller bed 12. The operator then closes the manual switch MS-l, Figure 6, to start the driving motor 34 and the drive rollers 32 thereby conveying the stack S along the transfer roller bed 12 in the direction of the upright frame 14. Motion of the stack S causes the limit switch LS-I to open, but the rollers 32 continue to be driven by the motor 34, Figure 6, so long as the switches LS3a and LS-4a remain closed. The lift platform 18 can be restored to its lowermost position at any time by the operator through the manual switch MS-2, and it can be herewith assumed that the lift platform 18 is in its lowermost position and free of any load whereupon the switches LS3a and LS-4a are closed to cause the drive rollers to drive the stack off the bed 12 and onto the platform 18. Momentum of the stack S on the rollers 106 carries it to the position 8-1, Figure 3, at which the stack engages the stop 108 to arrest its progress and simultaneously closes the pressure switch LS4 to stop the roller bed motor 34, Figure 1. Closure of the normally open contacts LS4c in this switch LS4-completes the circuit 160, Figure 6, to energize the up relay coil UR and the by-pass relay coil BR, it being noted that the upper set of contacts a in the electromagnetic switch 162 is closed due to the energization of the PEG switch controlling the electromagnetic switch 162, Figure 6.

The energized up relay coil UR, Figure 5, causes the lift control valve 122 to deliver line pressure into the line 124 so as to drive the pistons 88 upwardly in-the 75 6. cylinders 86. Simultaneously free escape of the fluid from the upper chambers in the cylinders 86 is permitted by the energized by-pass valve 144 to cause rapid rise of the platform and sheets thereon. At a predetermined point the rapidly rising stack of sheets S, Figure 2, intertrupts the light source 147 to deactivate the PEG switch and accomplish two results; first, in Figure 6, the contacts a in the switch 162 are opened so as to release and close the by-pass valve 144 and retard upward motion of the platform 18 to feed speed rate and; second, the lower contacts b in the switch 162 are closed to initiate periodic energization of the electromagnetic coils 64 in the magnet and roller frame 16. Progressing at feed speed rate slowly upwardly, the stack in the position 8-1, Figure 2, has its top end moved into the field of influence of the coils 64, which field extends downwardly through the plane of the

rollers

68, 70 and thereby links with and attracts the top sheet from the stack. The limit switch LS-2 is opened by the magnetically lifted top sheet for temporarily deenergizing the up relay coil UR, Figure 6. The magnetized top sheet in moving vertically against the underside of the alternating live and

dead rollers

70, 68 is driven transversely to the right thereupon as viewed in Figure 2, so as to pass between the driven pinch rolls 72 and onto the conveyor 20 or other receiver to which the individual sheets are successively fed. The switch LSZ is thereupon released and recloses to reenergize the up relay UR and cause the stack to progress upwardly again, repeating in stages to magnetically unload one sheet therefrom at a time. Periodic energization of the coils 64 by the timer switch 170 in short pulses, provides intervening dead periods of 5 seconds duration to enable the departing sheet to completely uncover the stack prior to the pulse for the next sheet. Therefore, the next sheet is fully exposed for uniform application of the pulsed field when it occurs so that the sheet will come up generally level, and not with one end coming up before the other end can start to lift.

When the last sheet vacates the platform 18, the latter is in a closely confronting position to the magnet and roller frame 16 and in the event the lift platform overtravels its normal feed path, the switch LS2 is opened thereby, to cause the up relay UR to be open circuited and the lifting stopped. Meantime, inasmuch as the lift bed switch LS4 is released owing to the fact that the rollers 106, Figure 2, are no longer occupied, the contacts LS-4b thereof, Figure 6, close the circuit 156 to energize the down relay coil DR and simultaneously to disable the up relay circuit 160 through action of the electromagnetic interlock switch 158. The lift platform 18 is, therefore, restored to its lowermost position due to appropriate operation of the control valve 122, Figure 5, in its operating position 122a. Assumption of the lowermost position by the platform 18 closes the normally open contacts LS3a, Figure 6, and opens the normally closed contacts LS3b to interrupt downward movement of the platform and prepare it for another loading and lifting operation. The machine, proceeds with another automatic loading, destacking, and feeding cycle as soon as the operator moves the handle 44 and the manual switch MS-l, Figure 6, in the manner above set forth.

It is apparent that the PEG switch-controlled shift of the machine from fast rate to feed speed rate of lift, automatically compensates for the height of stacks being handled by the machine, and that each stack is initially lifted rapidly to the point at which its top sheet begins to enter the pulsating field of the lifting magnets. The idler rollers 68 in the magnet and roller frame 16 have the dual function of providing antifriction coasting engagement with sheets being conveyed therealong and providing a magnetizable metal path for the field from the salient field coil poles in the magnets 64. The live rollers 70 in the same frame 16 not only provide anti friction engagement with the sheets, but also rotate under torque to drive them in the direction in which they are tobe conveyed. It is appreciated that the magnetic suspending force collapses before each departing sheet has fully uncovered the remaining stack and the departing sheet naturally sags somewhat under gravity and tends to or actually does drag its trailing end against the stack. However, at this same time the upper and lower pinch rolls 22 are both in engagement with the leading end or the body portion of the sheet and hold it generally to its horizontal path without any actual necessity for further assistance from the electromagnetic coils 64.

Variations within the spirit and scope of the invention described are equally comprehended by the foregoing description.

I claim:

1. A sheet handling machine comprising a bed of conveyor rolls for conveying a stack of sheets and having a stack supporting section, a delivery conveyor having at least a portion thereof above and confronting said stack supporting section, power lift means effective to lift said section and a stack of sheets supported thereby toward said delivery conveyor, said power lift means having a reverse control mechanism, and means activated to create a field of force in space between said section and the confronting portion of the delivery conveyor to attract the sheets individually from a stack supported on said section and to suspend the same thereabove as the delivery conveyor conveys them away, said reverse control mechanism and said field creating means having control means sensitive to the presence of sheets on said stack supporting section and released when the section is vacated to automatically deactivate the field creating means and reverse the power lift means.

2. A sheet handling machine comprising a bed of conveyor rolls for conveying a stack of sheets and having a stack supporting section, a delivery conveyor having at least a portion thereof above and confronting said section, power lift means effective to lift said section and a stack of sheets supported thereby at a fast rate of progress toward said delivery conveyor, said power lift means having speed control mechanism therefor to reduce the rate of upward progress thereof and having a reverse control mechanism, means activated to create a pulsating field in space between said section and the confronting portion of the delivery conveyor to attract the sheets individually from a stack supported on said section and to suspend the same thereabove as the conveyor conveys them away, a control element connected to the speed control mechanism and sensitive to the upward progress of the stack being lifted to automatically reduce the rate of progress at a predetermined point of nearness of the stack to the delivery conveyor, and a sensing element interconnecting the stack supporting section and the reverse control mechanism in a manner to automatically reverse the power lift means when the element senses that the section becomes unoccupied.

3. A sheet handling machine comprising a bed of con veyor rolls for conveying a stack of sheets and having a stack supporting section, a delivery conveyor having at least a portion thereof above and confronting said stack supporting section, power lift means effective to lift said section and a stack of sheets supported thereby at a fast rate of progress toward said delivery conveyor, said power lift means having speed control mechanism therefor to reduce the rate of upward progress thereof and having a reverse control mechanism, means activated to create a field of force between said section and the confronting portion of the delivery conveyor to attract the sheets individually from a stack supported on said section and to suspend the same thereabove as the conveyor conveys them away, a control element connected to the speed control mechanism and sensitive to the upward progress of the stack to automatically reduce its rate of progress at a point at which the stack nears the influence of said field, and a control element for the field creating means and sensitive to stacks on the section to deactivate 8 the field when the last sheet of a stack vacates the stack supporting section.

4. Apparatus for destacking a stack of magnetically attractable sheets, comprising a frame having contact roller parts mounted thereto in a fixed common plane and having an adjacent support platform shiftable between a remote position and a position closely confronting the contact roller parts, a loading table for moving a stack of sheets into the apparatus and having drive means associated therewith and actuable to transfer the sheets therefrom onto the support platform in the remote position of the latter, means sensitive to the support platform occupying its remote position in unloaded condition to actuate the drive means and transfer sheets to the support platform, means directing an electromagnetic field through the plane of the contact roller parts when the platform is in its aforesaid confronting position and magnetically transferring the top sheet of the stack thereon against the contact roller parts, and drive means for causing the just transferred sheet to be transferred along the roller parts and out of the space between the stack and the roller parts.

5. Apparatus for destacking a stack of magnetically attractable sheets, comprising a frame having contact roller parts mounted thereto in a fixed common plane and having an adjacent support platform shiftable between a remote position and a position closely confronting the contact roller parts, a loading table for moving a stack of sheets into the apparatus and having drive means associated therewith and actuable to transfer the sheets therefrom onto the support platform in the remote position of the latter, means sensitive to the support platform occupying its remote position in unloaded condition to actuate the drive means and transfer sheets to the support platform, means actuable to direct an electromagnetic field through the plane of the contact roller parts, means sensing movement of approach of the sheets and shifting platform toward its aforesaid confronting position for actuating the field directing means to magnetically transfer the top sheet of the stack from the platform and against the Contact roller parts, and drive means for causing the just transferred sheets to be further transferred along the roller parts and out of the space between the stack and the roller parts.

6. Apparatus for destacking a stack of magnetically attractable sheets, comprising a frame having contact roller parts mounted thereto in a fixed common plane and having an adjacent support platform shiftable between a remote position and a position closely confronting the contact roller parts, a loading table for moving a stack of sheets into the apparatus and having drive means associated therewith and actuable to transfer the sheets therefrom onto the support platform in the remote position of the latter, means sensitive to the support platform occupying its remote position in unloaded condition to actuate the drive means and transfer sheets to the support platform, means actuable to direct an electromagnetic field through the plane of the contact roller parts, means sensing movement of approach of the sheets and shifting platform toward its aforesaid confronting position for actuating the field directing means to magnetically trans fer the top sheet of the stack from the platform and against the contact roller parts, means sensing when the platform is finally vacated by the sheets to deactivate the field creating means, and drive means for causing the just transferred sheets to be further transferred along the roller parts and out of the space between the stack and the roller parts. 7

7. Apparatus for destacking a stack of magnetically attractable sheets, comprising a frame having contact roller parts mounted thereto in a fixed common plane and having an adjacent support platform shiftable between a remote position and a position closely confronting the contact roller parts, a loading table for moving a stack of sheets into the apparatus and having drive means associated therewith and actuable to transfer the sheets therefrom onto the support platform in the remote position of the latter, means sensitive to the support platform occupying its remote position in unloaded condition to actuate the drive means and transfer sheets to the support platform, means actuable to direct an electromagnetic field through the plane of the contact roller parts, reversible lifting means for shifting the loading platform from remote position to confronting position, means sensing movement of approach of the sheets and shifting platform toward its aforesaid confronting position for actuating the field directing means to magnetically transfer the top sheet of the stack from the platform and against the contact roller parts, means sensing when the platform is vacated by the sheets to reverse the lifting means and lower the platform to its remote position, and drive means for causing the just transferred sheets to be further transferred along the roller parts and out of the space between the stack and the roller parts.

8. A bilevel handling machine having an upper level of power driven conveyor rollers and a lower level of conveyor rollers, a sheet supporting platform having power lift means for operating the same between levels to receive and transfer a stack of metal sheets from the lower conveyor rollers and toward the upper conveyor rollers, field creating means for magnetically attracting and individually suspending the uppermost exposed sheet of the stack against the underside of the upper rollers, and reverse mechanism for the power lift means having a pressure switch connected to the supporting area of the platform and released when the last sheet of the stack becomes exposed and is attracted away to automatically reverse the platform.

9. A sheet handling machine comprising a bed of conveyor rolls for conveying a stack of sheets having a stack supporting section, a delivery conveyor having at least a portion thereof above and confronting said section, power lift means eifective to lift said section and a stack of sheets supported thereby at a fast rate of progress toward said delivery conveyor, said power lift means having speed control mechanism therefor to reduce the rate of upward progress thereof and having a reverse control mechanism, means activated to create a field of force between said section and the confronting portion of the delivery conveyor to attract the sheets individually from a stack supported on said section and to suspend the same thereabove as the conveyor conveys them away, a control element connected to the field creating means and sensitive to the upward progress of the stack to automatically activate the field creating means at a point at which the stack nears the influence of said field, and a control element connected to the field creating means' and sensitive to the vacating of the stack supporting section by the last sheet of a stack to deactivate the field creating means.

10. A bilevel handling machine having an upper level of power driven conveyor rollers and a lower level of conveyor rollers, a sheet supporting platform having power lift means for operating the same between levels to receive and transfer a stack of metal sheets from the lower conveyor rollers and deliver the sheets to the upper conveyor rollers, field creating means energized for magnetically attracting and individually suspending the uppermost exposed sheet of the stack from the underside of the upper rollers, and mechanism for reversing the power lift means and deenergizing the field creating means, said mechanism having a pressure switch for controlling the same mounted to the supporting area of the platform and released when the last sheet of the stack becomes exposed and is attracted away to automatically reverse the platform and deenergize the magnetic field.

11. A bilevel handling machine having an upper level of power driven conveyor rollers and a lower level of conveyor rollers, a sheet supporting platform having power lift means for operating the same between levels to receive and transfer a stack of metal sheets from the lower convey-or rollers and deliver the sheets to the upper conveyor rollers, field creating means for magnetically attracting and individually suspending the uppermost exposed sheet of the stack from the underside of the upper rollers, feed speed mechanism for the power lift means having a device sensing the upward progress of a stack of sheets up on the platform for automatically changing the rate of lift of the latter from an initial speed to a feed speed, and reverse mechanism for the power lift means having a pressure switch connected to the supporting area of the platform and released when the last sheet of the stack becomes exposed and is attracted away to automatically reverse the platfo 12. A bilevel handling machine having upper and lower levels of power driven conveyor rollers, a sheet supporting platform having power lift means for operating the same between levels to receive and transfer a stack of metal sheets from the lower conveyor rollers and deliver the sheets to the upper conveyor rollers, first means activated to magnetically attract and individually suspend the uppermost exposed sheet of the stack against the underside of the upper rollers, reverse mechanism for the power lift means having a pressure switch connected to the supporting area of the platform and released when the last sheet of the stack becomes exposed and is attracted away to automatically reverse the platform, and activating means connected to the first means and included in circuit with said pressure switch so as to deactivate the magnetic field automatically upon release of the pressure switch.

13. Article transferring apparatus comprising the combination of upper and lower roller tables having controllable mechanism for causing their relative movement together at a fast rate and being slowable to a feed speed rate enabling the transfer of a stack of articles, one at a time, from the lower table, said upper table being of the inverted type with rollers having intermittently operable magnetic means arranged to temporarily hold the articles individually in -a suspended relation with said rollers, and stack end location responsive control means connected to said mechanism effective when the upper end of said stack approaches to predetermined proximity to the inverted table to slow said articles to feed speed rate and substantially simultaneously effective to cause at least one period of intermittent energizations of the magnetic means for operation in the above described manner.

14. Article transferring apparatus comprising the combination of upper and lower roller tables having controllable mechanism for causing their relative movement together at a fast rate and being slowable to a feed speed rate enabling the transfer of a stack of articles, one at a time, from the lower table, said upper table being of the inverted type with power driven rollers having intermittently operable magnetic means arranged to temporarily hold the articles individually in a suspended relation with said rollers, first and second means both governing the operation of said magnetic means, and top article location responsive control means connected to said mechanism operable by said first means in a manner to make said mechanism ready for slow running operation and substantially simultaneously to energize said magnetic means when the top one of the articles approaches to a predetermined distance away from the inverted table, and so long as top article of the existing stack exceeds said predetermined distance away to make said mechanism ready for fast running operation without energizing said magnetic means; and operable by said second means for establishing one of said running operations of said mechanism to cause said first means to be actuated and to reenergize said magnetic means solely in response to movement of the top article as it runs along the power driven rollers.

'15. Article transferring apparatus comprising vertically spaced roller tables between which successive stacks of the .articles are confined supported on the lower table, the upper table being of the inverted type with rollers having magnetic means in the bed thereof to temporarily hold'the articles individually in a suspended relation with said rollers, table reciprocating means for causing relative movement of said tables selectively in directions of approach and of separation to one another comprising differential piston and cylinder means connected to one of said tables, and stack location responsive control mechanism connected to said table reciprocating cylinder means operative to selectively apply line pressure to one end of said cylinder means to relatively move said tables in one of said directions under direct line pressure, and operative to apply line pressure to both ends of said cylinder means to relatively move said tables in the opposite direction under dilferential line pressure.

16. Article transferring apparatus comprising vertically spaced roller tables between which successive stacks of the articles are confined supported on the lower table, the upper table being of the inverted type with rollers having magnetic means in the bed thereof to temporarily hold the articles individually in a suspended relation with said rollers, table reciprocating means for causing relative movement of said tables selectively in directions of approach and of separation to one another comprising differential piston and cylinder means connected to one of said tables, and stack location responsive control mechanism connected to said table reciprocating cylinder means operable to selectively apply line pressure to one end of said cylinder means to relatively move said tables in a direction at one rate, operable to apply line pressure to both ends of said cylinder means to relatively move said tables at a rate in the opposite one of said directions, and operable to change said table movement to a slowdown rate as they approach one extreme of their relative travel in one of said directions.

17. Article transferring apparatus comprising vertically spaced roller tables between which successive stacks of the articles are confined supported on the lower table, the upper table being of the inverted type with rollers having magnetic means in the bed thereof to temporarily hold the articles individually in a suspended relation with said rollers, table reciprocating means for causing relative movement of said tables selectively in directions of approach and of separation to one another comprising differential piston and cylinder means connected to one of said tables, and stack location responsive control mechanism connected to said table reciprocating cylinder means comprising a plurality of article-sensing switch contacts, one of said switch contacts formingpart of a bed switch located in the roller bed of said lower roller-table operativeto selectively cause application of line pressure to one end of said cylinder means to relatively move said tables in a direction at one rate, a similarly located switch contact operative to selectively cause application of line pressure to both ends-of said cylinder means to relatively move said tables at a rate in the opposite one of said directions, and a photocell switch contact operative to change the effective rate of pressure application in said cylinder means to set it in slow-down movement as the tables approach an extreme of their relative travel in one of said directions.

18. Article transferring apparatus comprising vertically spaced roller tables between which successive stacks of the articles are confined supported on the lower table, the upper table being of the inverted type with rollers having magnetic means in the bed thereof to temporarily hold the articles individually in a suspended relation with said rollers, table reciprocating means for causing relative movement-of said tables selectively in directions of approach and of separation to-one another and having a reversible drive, and stack location responsive control mechanism connected to said table reciprocating means comprising sets of contacts common to a single bed switch in the table of rollers in the lower table, operation of one set of said switch contacts in response to deposit of a single article or the lowermost article of a stack onto said lower table causing said table reciprocating means to relatively move said tables in one of said driven directions, and operation of another set of said switch contacts in response to vacation of said lower table by an article as aforesaid causing the drive of said head reciprocating means to reverse.

Moore Oct. 1, 1935 Hamilton Sept. 29, 1953 w... in