EP0510338A1

EP0510338A1 - Method and apparatus for stacking sheet material

Info

Publication number: EP0510338A1
Application number: EP92104022A
Authority: EP
Inventors: Robert E. Welty
Original assignee: IOWA PRECISION INDUSTRIES Inc; Iowa Precision Ind Inc
Current assignee: IOWA PRECISION INDUSTRIES Inc; Iowa Precision Ind Inc
Priority date: 1991-04-24
Filing date: 1992-03-09
Publication date: 1992-10-28
Also published as: CA2066910A1; JPH05213508A

Abstract

An apparatus for stacking and separating thin sheet material after it is cut into pieces of a predetermined size. The apparatus utilizes suction cups carried on several, independent chains that are moving in parallel directions and in the direction of movement of the material to be stacked. As the material is fed into the apparatus, it is gripped by the suction cups, cut to length and then separated slightly by moving the independent chain drives laterally and then breaking the vacuum in the suction cups so as to release the pieces into separate stacks. The chain drives are then moved laterally back to their original positions and the cycle is repeated. The apparatus uses a unique suction cup-valve arrangement that eliminates the need for vacuum lines.

Description

The present invention relates to apparatus for stacking and separating thin sheet material.
Numerous products utilize thin sheet material, the material usually forming the housing or box covering the innerworkings of the product. Frequently, these materials are thin metal prepainted and supplied in coils to the product manufacturer. For example, in the manufacturer of refrigerators and other major appliances, prepainted pieces of relatively thin sheet steel are utilized. The material is received from the steel supplier in coils, and the sheet material must be uncoiled and cut to size. In high volume production operations, the precut pieces are stacked, and the stacks moved to the assembly line. When the material is cut from the original coil, the thin sheet pieces are somewhat difficult to handle, and if they are prepainted, great care must be exercised in the handling so as not to mar the surface.
It is known to use magnetics to handle these pieces after they are cut, but such machines are quite complex and expensive, and are not capable of handling multiple rows or stacks of pieces which must be properly separated. Moreover, if the coil of steel contains any foreign material, such as a light coating of oil, this can interfere with the ability of the electromagnets to grip the sheet material. Obviously, the use of electromagnets is limited to magnetic materials.
In order to overcome some of the disadvantages of using magnetism to stack and separate thin sheet material that has been cut from a coil, systems utilizing vacuum cups have been used. Such systems can be used with all types of materials, but air system for creating and supplying the vacuum to the cups that contact and grip the material is a rather complex system, and one that requires a considerable amount of maintenance to keep the system in proper operation. Obviously, in such systems, if leaks occur at any point in the vacuum supply system, the machine may malfunction. Also, as with the magnetic systems, there are no known machines for properly separating rows of pieces cut from the same coil.
Therefore the object of the present invention is to provide an improved apparatus that can be used with all types of thin sheet material and which will be relatively simple and less costly, than known machines.
The present invention provides an apparatus for stacking pieces of relatively stiff sheet material moving in a predetermined direction, said apparatus comprising a plurality of suction members moveable along a path above the sheet material and in the direction of the sheet material, carrier means for moving the suction members along the path, the path of the suction members being sufficiently close to the sheet material so that the suction members will engage the sheet material to grip it and carry it along the path, valve means operatively combined with each suction member to provide for the creation of a pressure differential that causes the suction member to grip and hold the sheet material, release means selectively engageable with the valve means to equalize the pressure and provide for release of the sheet material from the grip of the suction members, and means to control operation of the release means to provide for controlled release of the sheet material at the desired time onto a stack of sheet material.
In one embodiment the apparatus of the invention utilizes a plurality of relatively small suction cups, each cup having its own release valve, with a plurality of cups being mounted in line on an endless moveable chain or belt. A plurality of chains or belts, each containing a plurality of suction cups, the chains are mounted for movement in planes parallel to the direction of movement of the material to be stacked. With this basic arrangement, each of the chains and their respective drives are independently moveable relative to each other transversely to the direction of movement of the material, thus allowing a piece of material picked up by one of the drives to be moved away from the adjacent drive so that the pieces of material can be separated the desired distance for formation of separate, adjacent stacks. The apparatus utilizes a unique vacuum-suction cup which has its own valve that is normally closed. When the suction cup engages a piece of material and pressure is applied to the cup, the air between the cup and the material will be forced out, and as the edges of the cup are sealed on the material, a vacuum will be created allowing the cup to grip the material. The pressure is equalized merely by opening slightly the valve for each cup. This allows the cups gripping a piece of material to simultaneously release the material merely by tripping simultaneously the actuators for the valve of the cups holding the material. With the system of the invention, a piece of cut material can be picked up and held by a plurality of cups on a single chain drive, and a plurality of adjacent pieces can be picked up by independent drives mounted adjacent to each other. The drives are moveable transversely relative to each other so that the material can be moved laterally a predetermined distance before the cups release the pieces onto their respective stacks. With the apparatus and system of the invention, the pieces are gripped, cut, moved sideways and then dropped onto stacks in a quick and efficient manner.
The apparatus of this invention can be produced at a lower cost and will reduce substantially the amount of maintenance required by known machines.
In the drawings:

Figure 1 is a top or plan view of an apparatus constructed according to the principles of the invention;
Figure 2 is a side elevational view of the apparatus of Figure 1;
Figure 3 is an enlarged side elevational view of a drive unit that forms a part of the apparatus of the invention;
Figure 4 is an end elevational view of the drive unit of Figure 3;
Figure 5 is a schematic diagram illustrating the individual pieces stacked into multiple stacks; and
Figure 6 is a side elevational view of one of the individual valves of the drive unit.

In describing the apparatus of the invention, it should be understood that the stacker is normally part of a line of equipment that includes an uncoiler and a shear upstream from the stacker to which the invention relates. In other words, the stacker of the invention receives the individual pieces of thin material as they are cut by the shear and stacks them in one or more stacks. Therefore, the material is fed from a shear, represented schematically at 10, onto a guide plate 12 and a plurality of rollers 14. It will be understood that the type of material normally handled is a thin sheet of material, usually metal, and may or may not be prepainted. One of the advantages of the apparatus of the invention is that it can handle and stack prepainted material without marring the painted surface.
As the leading edge of the material is fed into the apparatus from the shear 10, the material has not yet been cut to the desired length. Cutting by the shear 10 into individual pieces of the desired length occurs while the leading edge of the material is in the stacker and held by it on top of the guide plate 12 and rollers 14. The length to which the individual pieces are cut depends upon how far the material is advanced into the stacker before being cut by shear 10. Therefore, the material can be cut to any predetermined desired length, as will be understood from the description hereinafter.
Figures 1 and 2 of the drawings illustrate two stackers positioned end to end, but it will be understood that in many applications, a single stacker will be used. Each of the stackers is positioned above a standard lift table 16 of any well known design. The purpose of the lift table 16 is to hold the stack of individual pieces of material until they are moved off the lift table for further processing or use. As such, and as is well known, the height of the lift table 16 is variable, with the lift table 16 automatically lowering in increments as the pieces of material are stacked on it so that the top level of the stack remains constant within an acceptable range. Such lift tables, and the system for automatically lowering or raising them, is well known to those skilled in the art, and lift tables are commercially available and commonly used. Therefore, further details of the lift table 16 will not be described since such details form no part of the invention.
Referring now to the stacker itself, the stacker as longitudinal extending side frame members 18 which are supported and positioned in any suitable manner so as to position the working portions of the stacker in proper alinement and height with the other components of the processing equipment. For purposes of clarity, the supporting components for the stacker have not been shown except as indicated in Figures 1 and 2 which show a portion of the vertical supports 20 connected to the side frame members 18 and therefore suspending the side frame members 18 above the lift table 16.
Each stacker includes a plurality of what are designated handling units each indicated by the reference numeral 22, there being four such handling units 22 shown. The number of handling units 22 will depend upon the particular application of the stacker and the number of stacks to be formed. In the preferred embodiment, there are shown four handling units 22 which will create three stacks, side by side, in the manner described hereinafter.
The handling units 22 are shown in detail in Figures 4, 5, and 6, each unit 22 consisting of a main longitudinal support member 24 connected to the vertical supports 20 (Figure 2). At the upstream end of the support member 24 are a pair of sprockets 26 mounted on shaft 28, while at the downstream end of support member 24 are a second pair of sprockets 30 driven by drive shaft 32 which is operatively connected to all of the units 22 to simultaneously power them. Sprockets 30 and 26 support and drive a pair of endless drive chains 34, there being one chain for each pair of sprockets 26 and 30. Connected to and spaced evenly along each of the drive chains 34 is a pickup unit 36 that is comprised of a valve 38 and a suction cup 40. As best seen in Figure 6, each pickup unit 36 is affixed to the chain 34 by L shaped links 42 and fasteners 44. As best seen in Figure 3, the pickup units 36 at the upstream end travel in a path that is somewhat irregular and brings each pickup unit 36 down at an angle so as to gradually engage the sheet material 46 to be picked up. This gradual engagement and angle of approach of the suction cup 40 of each pickup unit 36 is designed to assure positive engagement of the suction cup 40 with the sheet material 46 while preventing the edge of the suction cup 40 from being bent inwardly and malfunctioning. As best seen in Figure 3, the path of the pickup units 36 once the suction cups 40 have engaged the sheet material 46 is a straight path in a horizontal plane just above lift table 16.
In order to provide for positive engagement of the suction cups 40 with the sheet material 46 and permit controlled release, we have provided a simple and unique valve 38 that forms a part of the pickup unit 36. As best seen in Figure 6, the valve 38 has a U-shaped body 48 the bottom legs 50 of which are directed outwardly to facilitate attachment of the pickup unit 36 to the drive chain 34 in the matter previously described. However, the main part of the valve body 48 contains a lateral passageway 52 that communicates with a vertical passageway 54. Each suction cup 40 is removably attached to the body 48 by a threaded fastener 56 that contains an opening 58 extending through it so as to provide communication between the passageway 52 and the interior area of the suction cup 40. A valve member 60 extends through the lateral passageway 52 and has a first valve seat 62 at one end and a second valve seat 64 at the other end. Valve seats 62 and 64 seat against the outside surface of the body 48 to normally seal the ends of the passageway 52. Thus, with passageway 52 sealed by the seats 62 and 64, when force is applied to the suction cup 40 to force it against the smooth surface of the sheet material 46, the edges of the cup 40 will seal against the surface of the sheet material 46, and the pressure differential created between the atmosphere and the inside of suction cup 40 will allow the suction cup 40 to grip the material 46 with sufficient force that the material 46 can be easily held and moved under control of the handling units 22. Thus, the sheet material 46 can be advanced as the drive chains 34 move, and under the control of the drive chains 34 advancement of the sheet material 46 can be stopped at any desired position.
When the sheet material 46 is in the desired position above the lift table 16, and the shear 10 has cut the material 46 to the desired length, the piece of material 46 must be released from the pickup units 36 so that it can be stacked on the lift table 16. The apparatus of the invention provides a simple and positive release mechanism. All that is necessary to release the grip of a suction cup 40 on the material 46 is to break one of the seals 62 or 64. By making the valve member 60 of a soft and flexible material, adequate seals are provided between the seats 62 and 64 and the body 48. In order to break the seal, it is only necessary to move slightly one of the valve seats 62 or 64 until the seal between it and the main body 48 is broken. Since the material of the valve member 60 is soft and flexible, this can be accomplished by applying force generally transversely to the valve member 60. Because of the flexibility of the valve member 60, force applied to the outer end of valve seat 62 or 64 will bend the valve member 60 sufficiently to break the seal, thus equalizing the pressure and causing the suction cup 40 to release its grip on the piece of sheet material 46.
As best seen in Figure 6, to facilitate this action of breaking the seal between one of the valve seats, valve seat 64 extends outwardly a sufficient distance to accommodate an annular shaped actuator 66 formed of a wear-resistant material. A valve release bar 68 is supported along each side of the member 24 of each handling unit 22, the bar being supported on guide pins 70 which extend through slots 72 in the bar 68. Also, an actuating arm 74 is attached to bar 68 and extends upwardly where it is pivotly connected to the operating rod 76 of cylinder 78, which can be air or hydraulic operated. Thus, when cylinder 78 is actuated, the release bar 68 will be move forwardly and downwardly to engage the actuators 66 on the valve members 60 thereby releasing the grip of the suction cups 40 on the piece of sheet material 46. After release of each piece of sheet material 46, the piece will drop onto the stack being formed on the lift table 16, and as the leading edge of the material is advanced onto the guide plate 12 and rollers 14, the material will once again be picked up by the descending suction cups 40 traveling around sprockets 26. The process just described will then be repeated.
Since the material being discharged by the shear 10 may also be cut longitudinally, multiple pieces of sheet material 46 may therefore be produced during a single cycle of pick up and release by the handling units 22. In the preferred embodiment, there are shown four handling units 22. These units are all driven by drive shaft 32 which is powered by a single motor 80. Motor 81 drives a plurality of screws 86, 88, 90 and 92 which extend transversely to and are operatively connected to respective ones of the support members 24 of the handling units 22. Screws 86, 88, 90 and 92 are also connected by a suitable means, such as chains 94, to screws 86a, 88a, 90a and 92a, each of which is also operatively connected to respective ones of the support members 24 of handling units 22. In other words, screws 86 and 86a are driven simultaneously, as are screws 88 and 88a, 90 and 90a, and 92 and 92a. Also, at the upstream end of the stacker, cross member 98 interconnects the vertical supports 20 in a manner to allow the vertical supports 20 to move along the cross member 98 as the handling units 22 are moved transversely by the screws 86, 88, 90 and 92. Control wheels 100 are provided at the end of each of the screws 86, 88, 90 and 92 to allow manual positioning of the handling units 22 laterally across the path of travel of the sheet material 46. This permits the handling units to be properly positioned depending upon the number of stacks of the material to be formed. Also, by activating or de-activating suitable clutches 102, the operator can select which of the screws 86, 88, 90 or 92 are turned when the motor 81 is engaged. This allows the operator to select which of the handling units 22 will be moved laterally during a cycle of operation so as to separate the pieces of sheet material 46 and place them in the proper stacks. Figure 5 schematically illustrates three separate stacks laterally spaced apart.
To form three stacks of material, the apparatus is programmed so that when the clutches 102 are engaged with screws 86 and 92, the two outer handling units 22 will move outwardly a slight distance away from the two inner handling units 22. If the pieces of sheet material 46 have been cut longitudinally to form three stacks as illustrated in Figure 5, the two inner handling units 22 will be engaged with the piece of sheet material in the center and marked "B" in Figure 5, while the two outer handling units 22 will be engaged with the outer pieces of sheet material 46 marked "A" and "C" in Figure 5. After the sheet material 46 has been advanced to the proper predetermined distance by the handling units 22, the handling units 22 are stopped. Motor 81 is then engaged to move the two outer handling units 22 outwardly to separate sheet material "A" and "C" from sheet material "B". At this time, cylinder 78 is actuated for each of the handling units 22 to cause the release bar 68 to engage the actuator 66 and allow all three sheets "A", "B" and "C" to be released onto the lift table 16.
The structure shown in Figure 5 is not illustrated in Figures 1, 2 or 3, but it should be understood that this structure would be positioned beneath the handling units 22 just above the lift table 16 with the cross supports 104 and 106 supporting a plurality of separator plates 108.
As previously indicated, Figure 1 shows two identical stackers which are operatively connected together by a sprocket 110 on drive shaft 34, chain 112 and sprocket 114. Thus, the two stackers can be operated and coordinated or can individually be operated as well. Illustration of the two stackers positioned end to end illustrates the variety of applications and flexibility of use of the principles of the invention.
The invention has been described in connection with the preferred embodiment of it which carriers out the principles of the invention. By providing handling units with a plurality of suction cups combined with valves that are of the utmost simplicity, the invention eliminates the need for vacuum lines and complex valving and control arrangements. By the use of the suction cup arrangement and its simplicity, the invention can be used to handle all types of materials, not just those metallic materials for which magnetic systems have been designed. The simplicity of the system is evident from the foregoing description. In addition, the capability of selectively moving multiple handling units laterally depending upon the number and spacing of the stacks of material desired, provides for use of the apparatus of the invention in many different applications. Also, by proper control systems, a single apparatus can be varied depending upon the particular size of material being produced at any particular time.
Having thus described the invention in connection with the preferred embodiment thereof, it will be evident to those skilled in the art that various revisions and modifications can be made to the preferred embodiment described herein.

Claims

An apparatus for stacking pieces of relatively stiff sheet material moving in a predetermined direction, characterized by said apparatus comprising a plurality of suction members (40) moveable along a path above the sheet material and in the direction of the sheet material, carrier means (34) for moving the suction members along the path, the path of the suction members being sufficiently close to the sheet material so that the suction members will engage the sheet material to grip it and carry it along the path, valve means (38) operatively combined with each suction member (40) to provide for the creation of a pressure differential that causes the suction member to grip and hold the sheet material, release means (68) selectively engageable with the valve means (38) to equalize the pressure and provide for release of the sheet material from the grip of the suction members, and means (76, 78) to control operation of the release means (68) to provide for controlled release of the sheet material at the desired time onto a stack of sheet material.
The apparatus of Claim 1, characterized in that the suction members (40) are operatively connected to an endless conveyor (34) moving in a plane generally perpendicular to the sheet material and parallel to the direction of movement of the sheet material.
The apparatus of Claim 2, characterized in that the suction members (40) are generally cup-shaped so as to form a chamber inside the member when engaged with the sheet material, and the valve means (38) has a passageway (52, 54) connected to the chamber and to the atmosphere, the passageway being normally closed by the valve means.
The apparatus of Claim 3, characterized in that the valve means (38) includes an actuator (66) moveable to open and close the passageway (52, 54), the actuator normally closing the passageway and being engageable by the release means (68) to open the passageway.
The apparatus of Claim 4, characterized in that the release means includes a member (68) operable to engage a plurality of the actuators (66) simultaneously so as to release the grip of a plurality of suction members (40) simultaneously.
The apparatus of any of Claims 2 to 5, characterized in that the endless conveyor is a chain (34) and a pair of sprockets (26, 30) are operatively engaged with the chain to drive the chain along said path.
The apparatus of any of Claims 1 to 6, characterized in that there are a plurality of carrier means (34) for moving the suction members (40) along parallel paths, the carrier means being spaced-apart laterally of said paths, selected ones of said carrier means being moveable laterally outwardly at selected times to provide for stacking of sheet material in multiple stacks separated from each other.
The apparatus of Claim 7, characterized in that the carrier means (34) are operatively connected to screws (86, 86a; 88, 88a; 90, 90a and 92, 92a) extending laterally of the paths and turnable to move the carrier means laterally.
The apparatus of Claim 8, characterized in that each carrier means includes a pair of endless chains (34) operable in parallel planes, the suction members (40) being operatively connected to the chains, and means to simultaneously drive the chains in each carrier means.