Method and apparatus for processing metal blanks

Abstract: Blank washer for cleaning individual sheet metal blanks with a drawing compound liquid suitable for press operations which employs pressurized liquid vortex diffuser means to replace conventional scrubbing brushes. An enclosure with air knives at entrance and exit to the blank washer provides closed loop recirculating of both air and cleaning liquid, which is filtered and repumped to plenum chambers feeding individual vortex diffuser cylindrical outlets which discharge liquid vortexes in close proximity to the passing sheet metal.

Description: BACKGROUND OF THE INVENTION In metal stamping plants, such as engaged in forming body components for the automotive industry, flat sheet metal blanks must be cleaned and treated with a liquid drawing compound preparatory to the forming operations. In conventional practice, a stack of blanks, which may have been sheared or die cut to irregular shapes preparatory to forming, are automatically fed through a washing station in which rotary brushes are supplied through tubular hubs with a fluid cleaning and drawing compound and distributed by the brushes to the passing surfaces of the blank. Wringer rollers are employed to drive the blanks and retain the liquid within the station and meter such liquid for drawing purposes. Surplus drawing compound flowing off the surface of the blanks is collected in a tank under the brushes and recycled through filters before return to the brushes. Such operations are subject to certain problems: Blank edge engagement of the brush bristles may include irregular burrs tending to cut or pull the bristles loose. They may adhere, on occasion, to the surface of the blanks admitted to the forming press where they may be pressed into the surface creating imperfections, particularly objectionable in light gauge sheet metal of which current automotive bodies are formed. In addition, grit and debris on the blank surfaces accummulated from preceding operations are not always effectively removed by the brush action, particularly as the brushes accumulate deposits picked up from the blank surfaces. Furthermore, the brushes and wringer rollers are subject to rapid wear and attrition involving the expense of frequent shut down and replacement. In addition, it is known to utilize compressed air to strip or remove excess fluids from the surfaces of the sheet metal blanks, see e.g. US-A-3 935 041 and GB-A-567 417. BRIEF DESCRIPTION OF THE PRESENT INVENTION The invention and further developments thereof are defined in the claims. Applicants have found that effective cleaning and coating of the blanks with a liquid drawing compound may be produced by "vortex diffuser" action dispensing with any requirement for brushes or any physical nonfluid contact with the blank surfaces in the vortex diffuser treatment of the blanks. A plurality of vortex diffusers arranged in staggered relation extending from plenums for fluid supply, have cylindrical discharge openings in close proximity to each of the too flat blank surfaces with a planar surrounding surface extending parallel to each blank surface confining outlet passage for the fluid leaving the cylindrical vortex chambers. By staggering adjacent rows of vortex diffuser outlets, full or overlapping coverage of the passing blank surface by opposing cylindrical vortex outlets may be achieved. An enclosure for the vortex diffuser plenums confines the discharge to a filtering and recirculating system pumped into the plenums. Air knives at either extremity of the enclosure confine the liquid discharged from the vortex diffuser to a tank under the enclosure. An exhaust duct at the top of the enclosure leads to an air/liquid separator from which a blower draws the separated air for return to plenums for the air knives. Accordingly, a "closed loop" system for both liquid and air is provided to minimize vapor discharge to the surrounding plant. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic side elevation of a preferred embodiment of the invention; Fig. 2 is a plan view taken along the line 2-2 of Fig. 1; Fig. 3 is a sectional view taken along the line 3-3 of Fig. 2; Fig. 4 is a fragmentary sectional view taken along the line 4-4 of Fig. 2; Fig. 5 is a fragmentary sectional view taken along the line 5-5 of Fig. 2; Fig. 6 is a fragmentary sectional view taken along the line 6-6 of Fig. 2; Fig. 7 is a sectional view taken along the lines 7-7 of Fig. 6; Fig. 8 is a sectional view taken along the line 8-8 of Fig. 7; Fig. 9 is a fragmentary sectional view taken along the line 9-9 of Fig. 6; Fig. 10 is a enlarged view of a single vortex diffuser unit such as illustrated in Fig. 9; and Fig. 11 is a sectional view taken along the line 11-11 of Fig. 10. DETAILED DESCRIPTION OF THE DRAWINGS With reference to Figs. 1-3 illustrating a preferred embodiment of the present invention, conventional brushes are replaced by two transverse banks of opposed vortex diffuser units generally indicated at 10. A blank stack and feed system similar to the prior art, feeds individual blanks across entrance guide rolls 11, between a pair of fixed air rail vortex diffuser units 12, across powered feed rollers 13 having pinch rolls 14 above, between opposed vortex diffuser heads 15, past exit drive rolls 16 having pinch rolls 17 above, through a second pair of fixed air knives 18, and past exit guide roll 19. Enclosure 20 schematically illustrated in Fig. 1 has interior walls which confine liquid cleaning and drawing compound employed in vortex diffusers 10, such as "Parker 410" cleaner/drawing compound mixed with a 9:1 ratio of water, "Parker 101" oil base to prevent rust, or "Quaker 61-MAL-HCL-N₂", to drop into tank 21 for return to a filtering and recirculation system 22 such as currently employed in conventional blank washing systems available from the Hyrdromation Company under the trade designation "Hydro-Vak". Filtered and recirculated liquid is pumped at 23 into plenums for diffuser heads 15 which extend across the width of vortex diffuser system having constant supply communication with all of the individual vortex diffusers 24. Air is drawn from the top of enclosure 20 through air duct 25 into an air/liquid separator 26 by recirculating blower 27, distributing the separated air under pressure through manifold pipes 28 to each of the air plenums 12 and 18, where outlet air knives 29 confine liquid from escaping through the blank washer passages and provide cleaned blanks from the exit substantially free of liquid but with a coating of drawing compound as required. With reference to Figs. 2 and 5, recirculating air is supplied to both plenums 12 through descending delivery pipes 30; and with further reference to Fig. 6 recirculated liquid from pump 23 is delivered through pipe 31 leading to ascending outlets 32 and vortex diffuser plenums 15, in each case shown differently in schematic Fig. 1. With reference to Figs. 6-11, each vortex diffuser assembly comprises a plenum 33, and vortex diffuser head 15, which has a closure plate 34 covered with a a plurality of diagonal nested dual vortex diffuser units 35, each bolted to the cover plate through three holes 36. Each vortex diffuser unit has two circular outlet ports 37 at the terminal end of a right cylindrical wall 38 where the high velocity vortex is generated. Each outlet port 37 terminates in a common plane 39, which is positioned relative to a passing sheet metal blank with approximately 3,2 mm (1/8") clearance for both blank surfaces. For each dual vortex diffuser unit 35, cover plate 34 is provided with four passages 40 for conducting liquid under pressure from the plenum chamber to cavities surrounding square enclosures 41 for each of the two cylindrical walls 38. As best shown in Fig. 10, each square enclosure 41, within cavity 42 is provided with a tangential slot 33 at each of the four corners leading to the periphery of cylindrical wall 38, whereby circular vortexes are generated to impinge on passing blanks. The staggered relation of the adjacent dual vortex diffuser units provides a tangential relation for full surface coverage of a passing blank in order to effectively clean the entire surface through the vortex action. In a typical installation, automotive body sheet metal blanks having a thickness of 0,71-0,76 mm (0.028 to 0.030 of an inch), pass between air knives and vortex diffuser head with 3,2 mm (1/8") clearance at both top and bottom surfaces. A width capacity of 213,4 cm (84") will accept blanks of any rectangular or irregular configuration with plenums adapted to supply all vortex diffusers regardless of blank size. Ajdustable feed speed range, up to 152,5 m/min (500 feet per minute), will normally be set for intermittent blank feed synchronized with stamping press operation. Vortex units are provided with liquid pressure in the range of 1,17-1,38 bar (17-20 psi) and air knife plenums with air pressure in the order of 0,069 bar (1 psi). A tank for such installation has 3400 l (850 gallon) capacity with 140 l/min (35 gallons per minute) passing through the filter. Molded plastic dual vortex diffuser units are made with a material supplied by General Electric under the tradename "Supec", (polyphenylene sulfide) G-401, 40% glass-filled and 1% P-DOX foaming agent.

Claims: Blank washer for cleaning sheet metal blanks, including a conveyor for conveying said sheet metal blanks along a path through said washer characterized by pressurized liquid vortex diffuser means (10) positioned to discharge a plurality of high velocity liquid vortexes into direct impingement on both surfaces of said sheet metal. Blank washer of claim 1 with said vortexes spaced to provide at least substantially contiguous impingement contact path surface coverage. Blank washer of claim 2 wherein said vortexes are spaced laterally and longitudinally in staggered relation relative to the path of said sheet metal. Blank washer of claim 2 including a plenum supply chamber (33) for the vortex diffuser means (10) on each side of said sheet metal. Blank washer of claim 2 wherein said vortexes discharge from said vortex diffuser means (10) in approximately 3,2 mm (1/8") proximity to each passing surface of said sheet metal. Blank washer of claim 5 wherein said proximity is established by a common planar surface (39). Blank washer of claim 6 wherein said vortexes discharge from circular outlets (37) in each planar surface (39). Blank washer of claim 7 wherein said vortex diffuser means (10) includes a right cylindrical surface (38) leading to each circular outlet (37). Blank washer of claim 8 wherein tangential porting (33) is provided into said cylindrical surface (38) to generate said vortexes. Blank washer of claim 9 wherein said tangential porting (33) is provided at four 90° spaced corners. Blank washer of claim 8 wherein said cylindrical surfaces (38) are provided in hollow units having said tangential porting (33) molded therein. Blank washer of claim 11 wherein said hollow units are molded plastic. Blank washer of claim 12 wherein said hollow units are molded in obliquely extending dual outlet units stacked laterally across the width of said blank washer. Blank washer of claim 13 wherein an appertured cover plate (34) is interposed between said plenum supply (15) and said hollow units. Blank washer of claim 4 including an enclosure (20) for said vortex diffuser means (10) to contain the discharge of liquid flowing off the surface of said sheet metal. Blank washer of claim 15 wherein said enclosure includes a tank (21) under said vortex diffuser means (10) to receive said discharge. Blank washer of claim 16 including filter means (22) for the liquid discharged into the tank. Blank washer of claim 17 including a recirculating pump means (23) for drawing liquid from said tank (21), and pumping it back into said vortex diffuser plenums (15). Blank washer of claim 18 including a supplemental filter screen for liquid drawn into said pump. Blank washer of claim 15 including air knife means (29) at the entrance and exit of said enclosure (20) directed toward the interior of said enclosure (20) to minimize liquid discharge from the entrance and exit for said sheet metal. Blank washer of claim 20 including a recirculating means for the air directed into said enclosure. Blank washer of claim 21 including an air/liquid separator (26) and a blower means (27) for recirculating separated air to said air knives (29). Blank washer of claim 20 including plenum means (12) for supplying air to said air knives (29) on either side of said sheet metal at both entrance and exit to said enclosure. Blank washer of claim 20 including a closed loop system for recirculating liquid discharged through said vortex diffuser means (10) and air discharged through said air knife means (29) to restrain both from passing out of said blank washer enclosure. Blank washer of claim 1 wherein said vortex diffuser means (10) is provided with pressurized liquid within a range of approximately 1,17-1,38 bar (17-20) psi. Blank washer of claim 1 including means (13) for feeding sheet metal at an adjustable linear speed. Blank washer of claim 26 including means (13) for feeding sheet metal at an adjustable linear speed up to 152,5 m/min (500 feet per minute). Blank washer of claim 20 wherein air pressure is provided by said blower (27) in the order of 0,069 bar (1 psi).

Inventors: NEUMANN JOHN W, NEUMANN SCOTT J, NEUMANN, JOHN W.,, NEUMANN, SCOTT J.
Applicants: NEUMANN IND INC, NEUMANN INDUSTRIES, INC.
Application year: 1991
Main classification: B08B3
IPC codes: B08B3, C23G3