PROCESS AND APPARATUS FOR FLATTENING SHEET GAUGE METAL SCRAP

Abstract: A novel process is disclosed by which contorted or distorted sheet gauge steel and other metal scrap material, gen­ erated by stamping and other deforming metal-working operations, is flattened by rolls (50,60) for the purpose of increasing the bulk density and to provide a scrap product that can more efficiently be transported and used for remelting in steel-making and foundry furnaces. The process involves the steps of feeding contorted sheet metal scrap between a pair of moving compressive surfaces, compressing the scrap to substantial flatness, and discharging the flattened steel scrap. The novel apparatus for performing the process is also disclosed.

Description: Background of the Invention . 1. Field of the Invention. The invention relates to sheet gauge metal scrap, and to the treatment and processing of such scrap material to facilitate its remelting and re-use in steel making and foundry furnaces. In particular, the invention relates to a process and apparatus in which sheet gauge steel and other metal scrap, produced by stamping and other metal-working operations, is flattened for the purpose of increasing its bulk density to enable it to be transported and used more efficiently in steel-making and foundry furnaces. 2. Description of the Prior Art. When sheet metal parts are formed in a stamping press, the scrap metal residue is typically bent, deformed, contorted, or distorted in some fashion, so that a piece of flat metal, which is inputted to the stamping process, and has a planar thickness in the range from about 0.3 to about 4.0 mm, is distorted by stamping so that the individual pieces of scrap from the stamping operation have a contortion (or deflection from flatness) of up to about 130 mm. This scrap has value, and it is desirable to recover this value by converting the scrap to a form in which it can more conveniently and economically be transported and then used as charge for a steel-making or foundary process furnace. The typical maximum dimensions of the individual pieces of sheet gauge steel or other metal that constitute the scrap which is the feed material for the process of this invention are approximately 1.5 m by 1.5 m, with a contortion of about 130 mm. The prior art process for taking this scrap and putting it into a more desirable form for transportation and reprocessing is commonly known as "baling." In the "baling" process, a batch of sheet gauge scrap metal, for example 7 kN, is charged into the so-called baling box of a baling press. In a typical example, the baling box will have a rectangular horizontal cross-section and the walls of the baling box will be rigid. After a batch of sheet gauge scrap metal has been charged into the baling box, hydraulically driven rams compress the charge into a relatively dense cubic "bale" or bundle having dimensions of, for example, 0.6 m by 0.6 m by 0.9 m. This bale or bundle is more easily transportable and usable in remelting operations. The bales or bundles produced by the prior art have two distinct disadvantages. First, the bales are not as desirable in modern steel-making technology as the loose, flattened, sheet scrap consisting of discrete pieces. Until 1960, the bulk of steel-making was performed in open hearth furnaces and the scrap charge was designed for such furnaces since the open hearth furnace operated well using bulky scrap pieces in the form of bales or bundles. Today, however, the open hearth furnace virtually is extinct, and steel-making normally is performed in basic oxygen or electric furnaces. These new furnaces operate more efficiently with a scrap charge made up of relatively small, free-flowing, discrete pieces. This type of scrap results in higher production rates and less damage to furnace linings and electrodes than bulkier scrap such as bales or bundles. The second disadvantage of the bales or bundles produced by the prior art is that the baling process has much higher costs associated with initial investment, energy consumption, maintenance, and manpower than does the process provided by the Invention. GB-A-1,063,731 and US-A-2,087,806 describe apparatus each comprising a pair of parallel opposing rigid compression roles, means for driving the roles in opposite senses, and means for interconnecting the roles for creating a compressive force therebetween. Neither document relates to an apparatus for increasing the bulk density of contorted pieces of sheet gauge metals scrap material. In contrast, while US-A-2,087,806 is concerned with an apparatus for separating metallic articles, GB-A-1,063,731 deals with a rolling machine for the manufacture of substances such as printing inks. Object of This Invention It is an object of this invention to provide an improved apparatus and process for taking pieces of sheet gauge metal scrap material which have been contorted from their original planar configuration, and converting them to a more planar configuration having a greater bulk density and being therefore more usable as scrap feed to a steel-making or other furnace. Summary of the Invention . The invention is directed to a process and apparatus for flattening sheet gauge metal scrap material, which is the result of stamping or other metal-working operations, and the pieces of which are significantly distorted or contorted from original planar shape, into a more planar configuration for easier handling, transporting and remelting. As used herein, "sheet gauge metal scrap material" refers to pieces or "clips" of steel or other sheet metal having a thickness of up to about 4 mm, typically having significant non-planar surfaces, and often having significant irregular interior and exterior shapes. Pieces or "clips" of sheet gauge metal scrap material are collected and fed from a suitable hopper into a feed chute and past a deflector/sensor gate, and then through a pair of hydraulically driven compression cylinders, which flatten the individual pieces of sheet gauge metal scrap material into irregular, but substantially more planar scrap material. This product scrap material is discharged from the compression rolls into a discharge chute and onto a discharge conveyor, and then can be collected in suitable containers, and transported and used as scrap feed material for an electric furnace or other process. The product of the invention is a mass of discontinuously overlapped, substantially more planar pieces of sheet guage metal scrap material, having individual thicknesses of up to about 4 mm, and which lie horizontally, one on the other, and conform readily to the shape of suitable containers. Description of the Drawings . Figure 1 is a schematic, vertical cross-sectional view of an apparatus of the invention; Figure 2 is a schematic, vertical cross-sectional view of an apparatus of the invention wherein one of the compression cylinders is in the deflected position for relieving an accumulating sheet gauge metal scrap feed; and Figure 3 is a perspective view of an apparatus for practicing the process of the invention. Detailed Description of the Invention . The invention relates to a process and apparatus for converting sheet gauge metal scrap material into substantially flat, relatively more dense and easily transported and handled pieces for use in charging steel furnaces, and particularly electric furnaces for steel making. The pieces of contorted sheet gauge metal scrap commonly generated in the conventional metal-stamping plant typically have a bulk density of from about 0.16 to about 4 kN/m³, and a principal object of this invention is to create a substantially more planar product having a bulk density in the range from about 6 to about 20 kN/cm³, and preferably at least about 8 kN/m³. Sheet gauge metal scrap material preferably used as feed or input to the process of this invention has exterior dimensions of about 1 m by about 0.3 m and a planar thickness or "gauge" of from about 0.3 mm up to about 1.3 mm. The maximum amount of contortion, or deflection from flatness, is about 130 mm in each piece. Viewing Figure 1, it will be seen that pieces or "clips" of sheet gauge metal scrap 10 are fed from conveyor 26 and fall by gravity through the feed chute 20. Conveyor 26 is of a conventional design and forms no part of this invention. Feed chute 20 is comprised of planar surface 22, made of hard sheet metal, and mounted at an angle of approximately 55° from the horizontal. The angle is not critical, but 55° has been found to provide good gravity feed of the sheet metal scrap to the pinch rolls 50 and 60. The opposite surface of the feed chute 20 is formed by a deflector/sensor gate 30, which comprises a pivoted, counter-weighted hard metal flat surface plate 32, which is pivoted about pivot point 34, and is counter-weighted by suitable counter-weight 36. The deflector/sensor gate 30 is mounted so that the pivot point 34 is approximately co-axial with the center of the feed chute conveyor roller 28 and so that when gate 30 is in its normal vertical position (shown in Figure 1), a gap of about five inches exists between the end of gate 30 and the surface 22 of feed chute 20. This gap serves to guide the individual clips of sheet gauge metal scrap material 10 toward pinch rolls 50 and 60. The two pinch rolls rotate in opposite clockwise and counterclockwise directions toward each other to provide a positive downward drive of sheet metal clips 10 between the pinch rolls. In a preferred embodiment of the invention, there are two hydraulic cylinders 54, one mounted at each end of the pinch rolls. Each of the two hydraulic cylinders 54 which interconnect pinch rolls 50 and 60 at opposite ends thereof will exert a compressive force of from approximately 57 kN to approximately 112 kN. At these force levels, the cylinder arms or pistons 56 will move freely to accommodate the varying thicknesses of the sheet gauge metal clips 10 flowing between the rolls. As seen in Figure 1, the axis of rotation of movable pinch roll 60 is located at an angle of approximately 20° from the horizontal plane including the axis of pinch roll 50, thereby causing the weight of pinch roll 60 to add a component of compressive force to the metal scrap material 10 while providing a positive gravity feed of the metal scrap into the juncture of pinch rolls 50 and 60. The piston 56 of each hydraulic cylinder 54 has its outer end pivotally mounted by pin 66 to a plate 68 which is rigidly attached to the pivotal arms 70. The compression or pinch rolls 50 and 60 and corresponding hydraulic drive motors 52 and 62 for rolls 50 and 60 are rotatably mounted on a suitable rigid steel frame 40. Roll 50 and its hydraulic drive motor 52 are rotatably mounted on the frame 40 and each hydraulic cylinder 54 is pivotally mounted to frame 40 by a pivot pin 64. Compression roll 60 and its hydraulic drive motor 62 are rotatably mounted between parallel arms 70, and the arms 70 are pivotally mounted at their lower ends to opposing sides of frame 40 by pins 72. As more fully described below, the rolls or cylinders will automaticlly open and reclose in response to a signal from the deflector/sensor gate 30 if there is a jam of material at the bottom of feed chute 20. The feed chute 20 is approximately 1.2 m wide and generally and preferably has a width which is at least 110% of the maximum dimension of the sheet gauge metal scrap clips 10 being fed therethrough. The throughput in the feed chute 20 can be of the order of 250 kN per hour, or more. The deflector/sensor gate 30 is a partially counterbalanced swinging plate 32, which is almost as wide as the feed chute 20. The counterweight 36 conveniently weighs from about 70 percent to about 90 percent, and preferably about 80 percent, of the weight of plate 32. Under normal conditions of continuous feed, individual pieces or clips of scrap will pass freely through the normal 0.13 m spacing at the lower end of gate 30, while overlapping pieces will be deflected for even distribution across the feed chute 20. In the event of a sudden material surge, a jamming of the pinch rolls 50 and 60, or roll stoppage, the gate 30 will be caused by the weight of accumulated material in chute 20 to rotate counterclockwise until it reaches a "relieving position" (shown in Figure 2), where its lower end will be positioned as much as, say, 0.5 m from the surface 22 of feed chute 20, which is four times the normal clearance. The exact "relieving position" spacing is a matter of choice. An electrical interconnection (not shown) between the deflector/ sensor gate 30 and the hydraulic compression cylinders 54 will activate the hydraulic compression cylinders 54 when the gate 30 is open to the "relieving" position to automatically cause pinch rolls 50 and 60 to open to provide a gap of about 0.6 m between them, as shown in Figure 2, and to permit the scrap material 10 which is backing up to fall clear. When it does fall clear, the gate 30 will return by gravity to a position which is at least 0.25 m from the chute 20, at which time the electrical interconnection (not shown) will cause the hydraulic cylinders 54 to return pinch rolls 50 and 60 to the normal operating position of Figure 1. Pinch rolls 50 and 60 are conveniently 1.5 m in diameter. This dimension is determined by the thickness and maximum contortion of the scrap material. The width of the rolls 50 and 60 desirably is 0.3 m greater than that of the feed chute, to allow for spreading of the scrap as it is received in the nip of the rolls. Pinch rolls 50 and 60 are conveniently fabricated from rolled 20 mm thick mild carbon steel plate with 115 mm diameter shafts, 12.5 mm thick end discs, and two 12.5 mm thick inner discs (not shown) evenly spaced between the end discs for each roll, as determined by roll diameter, width, and total compressive force. Each pinch roll is independently driven by an hydraulic motor, respectively designated 52 and 62 for rolls 50 and 60, at a varaible speed which can desirably be adjusted from about 6.5 to about 13 rpm, and which roughly translates to about 30 to about 60 m per minute of roll surface velocity for a 1.5 m diameter roll. The roll speed is determined by the average feed material flow rate, and both rolls are set to rotate at the same speed. The 40 kW hydraulic motors will exert a minimum torque of 11 kNm at 13 rpm. The flow rate of scrap material 10, and the compression force of pinch rolls 50 and 60, are adjusted to provide a bulk loading density in the range from about 6 to about 20, and preferably more than 8, kN/cm³ of the end-product scrap. A discharge chute 80, fabricated from hard sheet metal, is rigidly mounted to frame 40 below compression rolls 50 and 60 to receive the substantially flattened product clips exiting from the nip of rolls 50 and 60. These clips fall by gravity through discharge chute 80 and onto discharge conveyor 86, which transports the product clips to a convenient location for further handling. Preferably, discharge chute 80 has a concave longitudinal cross section, so as to deliver the product clips to discharge conveyor 86 without substantial impact with the surface of conveyor 86. The process of the invention is a process for taking sheet gauge metal scrap material 10, and converting it into a substantially more planar product having a bulk density in the range of from about 6 to about 20 kN/m³, and preferably at least about 8 kN/m³ and comprising pieces of not more than approximately 1.2 m width by not more than approximately 1.5 m length, and preferably pieces of not more than approximately 0.3 m width by not more than 1 m length. In the process, individual pieces or clips of sheet gauge metal scrap material are fed between a pair of spaced compression rolls under a combined total force exerted by the two hydraulic cylinders 54 of preferably approximately 225 kN, and are guided so that a relatively uniform feed of sheet gauge metal scrap pieces is fed through the pinch rolls at a linear velocity in the range from about 30 to 60 m per minute. The end product is a mass of discrete and substantially flattened pieces of sheet gauge metal scrap material, having a bulk density in the range from about 6 to about 20 kN/cm³. It will be appreciated that there is considerable variation that can be accomplished in the process and apparatus of this invention without departing from the scope of this invention, and that those variations are contemplated by this invention as claimed. For example, the dimensions of the sheet gauge metal scrap feed, the precise size and shape of the end product, the dimensions of the apparatus of the invention, and the loading and operating parameters of the hydraulic pinch rolls can be varied within broad limits within the scope of this invention as claimed.

Claims: An apparatus for increasing the bulk density of contorted pieces of sheet gauge metal scrap material, comprising: (a) a parallel pair of opposing rigid compression rolls (50, 60); (b) means (52, 62) for independently and variably driving each of said rolls (50, 60) in the same downward direction at their most proximate surfaces; and (c) means (54) adjustably interconnecting said compression rolls (50, 60) for creating a combined total compressive force between said rolls of from about 110 to about 225 kN. The apparatus of claim 1, in which the axis of rotation of one compression roll (50) is fixed and the axis of rotation of the other compression roll (60) is movably adjustable, and the movable axis of rotation is normally located at an angle from the fixed axis of rotation of approximately 20° above the horizontal plane through the fixed axis of rotation. The apparatus of claim 1 or 2, including: (a) a planar feed chute (20) for directing sheet gauge metal scrap material above and between said compression rolls (50, 60); and (b) a movable deflector/sensor gate (30) , normally providing a spacing at its lower end of approximately 0.13 m from the nearest surface of said feed chute (20). The apparatus of claim 3, wherein said feed chute (20) is inclined downwardly from the horizontal at an angle of approximately 55° and is positioned to discharge slightly above the line of proximity between said two compression rolls (50, 60), said deflector/sensor gate (30) is counter-weighted and pivotally mounted to increase said spacing with respect to said feed chute (20) in response to an accumulation of feed material, and means electronically connecting said deflector/sensor gate (30) and said means (54) adjustably interconnecting said compression rolls (50, 60) are arranged to provide a spacing between said compression rolls in response to a deflection of said gate (30) in excess of a predetermined amount. A process for increasing the bulk density of contorted pieces of sheet gauge metal scrap material, comprising the steps of: (a) introducing a feed consisting of contorted pieces of sheet gauge metal scrap material above and into the converging nip of an opposing parallel pair of oppositely-rotating rigid compression rolls (50, 60) in compressive contact with each other, with one said compression roll (60) having a movably adjustable axis of rotation; (b) passing said feed downwardly between said compression rolls (50, 60), whereby said contorted pieces of sheet gauge metal scrap material are subjected to a compressive force; and (c) removing from below the nip of said rolls (50, 60) a product consisting of pieces of sheet gauge metal scrap material having an increased bulk density. The process of claim 5, further comprising the step of actuating said compression roll (60) having a movably adjustable axis of rotation in response to an accumulation of feed material in the nip so that a spacing is provided between said compression rolls (50, 60). The process of claim 5 or 6, wherein the combined total compressive force between said rolls (50, 60) is in the range of from about 110 to about 225 kN. The process of any of claim 5 to 7, wherein said rolls (50, 60) are rotated in opposite directions to produce a downward tangential velocity at their surfaces in the nip of from about 30 to about 60 m/min.

Inventors: HERING, ALFRED GEORGE
Applicants: CONNELL LIMITED PARTNERSHIP
Application year: 1986
Main classification: B30B3
IPC codes: B30B3, B30B15, B30B9