Cryogenic tank and tank liner with curved flanges
United States Patent [1 1 [111 3,874,545  
 Struss Apr. 1, 1975 [54] CRYOGENIC TANK AND TANK LINER 1,286,628 12/1918 Herrman et a1. 220/5 R WITH CURVED FLANGES 1,287,019 12/1918 Herrman et al.... 220/5 R 1,358,203 11/1920 Herrman et a1.... 220/5 R X [75] Inventor: Leigh A. Struss, Nashua, NH. 1,417,617 5/1922 McNeil 220/5 R X Assigneez Martin Welding Inc. Lowe, Mass 1,428,337 9/1922 McNeil 220/5 R X 1 Flledi p 12, 1973 Primary Examiner-William 1. Price 21 A L N 350 349 Assistant Examiner-Steven M. Pollard 1 pp 0 Attorney, Agent, or FirmPearson &amp; Pearson Related US. Application Data [62] 3Di7vs5io2nl(l)f Ser. No. 226,640, Feb. 25, 1972, Pat. No. 57 S C I A tank liner sheet with an integral, curved, floor por- 52 us. Cl. 220/5 A, 220/1 B, 220/83, tion of diminihing Width and relatively high, curved 220/63 R side-edge flanges is made by a process which com- 51 Int. Cl B65d 7/02 prises holding the metal sheet substantially stationary 58 Field of Search 220/5 A, 5 R, 1 B, 63 R, on fixed Platform, While p g a series of roller 20/78 83 75 7 77; 52/245 benders, together with an edge-trimming device, along on an arcuate path adjacent to the sheet being [56] References Cited flanged. Special clamp means are used to minimize UNITED STATES PATENTS distortion in sheet position caused by stress on the h tb d. 362,107 5/1887 Penfield 220/5 R s ee emg processe 1.258538 3/1918 Dar1ey,.1r. 220/5 R 5 Claims, 9 Drawing Figures PATENTED APR 1 I975 snmlq g Mil Fig.2  
 CRYOGENIC TANK AND TANK LINER WITH CURVED FLANGES This application is a divisional application of Ser. No. 226,640 filed 2/25/72, now US. Pat. No. 3,765,211.  
 BACKGROUND OF THE INVENTION It has long been a problem to form sizeable flanges on elongate metallic sheets. This has been especially so when the flange followed an especially complex or compound curve&#34; type of path. Usually such flanges have been shaped by manual operations while they are held in a metal brake, an exceedingly expensive practree.  
  In US. Pat. No. 3,462,989, Fischer disclosed an apparatus for flanging sheet material, but Fischer was directing his efforts to forming simple flanges and does not attempt to solve the primary problem faced by applicants. i.e., that of forming a flange with a base line which defines a compound curve on the sheet. Another drawback to the apparatus defined by Fischer was the fact that a large amount of floor space is required for the operation of his apparatus.  
  Nowhere in the prior art has there been any suggestion of apparatus adapted to form complex flange configurations. Yet such apparatus would have a high utility, especially if it minimized the amount of residual strain left in the metal being worked, thereby providing not only an improved process but more reliable products adopted for utility in constructing such structures as, say, cryogenic tanks and the like.  
 SUMMARY OF THE INVENTION Therefore it is a principal object of the invention to provide an improved process and improved apparatus for forming flanged edges on metal sheet material, especially for forming sheets having compound curves along the flange line.  
  It is a particular object of the invention to provide apparatus for flanging the edges of sheet material which apparatus permits the operation to be carried out in minimal floor space.  
  A further object of the invention is to provide a means for forming flanges along sheets of varying width. and especially whereon the flanged area must curve with respect to the center line of an elongate sheet being processed.  
  Another object of the invention is to provide flanging apparatus such as described above which imparts a minimal amount of stress to the metal being worked, thereby making it dependable for use in construction of structures requiring very high structural reliability and integrity.  
  Another object of the invention is to provide relatively simple apparatus for making complex flanges on elongate sheet.  
  Still another object of the invention is to provide flanging apparatus which incorporates an integral and improved means for accurately trimming the edge of the material being flanged. v  
  A further object of the invention is to provide apparatus of the type described in the foregoing object whereby the sheet to be flanged is held in adaptive clamp means to minimize the effect of stresses exerted on the sheet during the flanging operation.  
  Other objects of the invention will be obvious to those skilled in the art on reading the instant invention.  
  In the practice of the invention, a thin elongate sheet is held on a stationary platform while a travelling rollerbender assembly, together with an edge trimmer, traverse one long edge of the sheet, each sequential rollerbending device in the assembly causing the edge of the sheet to be bent into a more upright position. Sheets to be so processed will usually be trimmed roughly beforehand; however, fine trimming is advantageously accomplished by use of an edge-trimming device mounted for movement with the roller-benders along the stationary platform.  
  The sheet is firmly clamped to the platform by means of convenient fastening devices at one end; at the other end, however, it has been found desirable to provide a pivoted pressure-clamp means. Most advantageously this clamp comprises a number of pivot points so that it may be self-adjusting to various stress vectors exerted thereon during the processing operation, and thereby insure that such stresses will not cause any undesirable warping of the sheet on the platform. It has been found that such bending stresses are minimized and most easily accommodated, when this clamp is used while a single side of the sheet is being flanged at a given time.  
  The platform has two tracks mounted along the sides thereof along which the roller-bender assembly with its rolling and trimming devices are carried during the processing operation. These tracks comprise arcuate sections positioned wherever necessary to achieve the appropriate curve for the flange. Most advantageously the curved sections are placed proximate to the fixed end of the sheet. In the typical case, this will be convenient because the curves desired in the sheet will be at one end, corresponding to a position in a structure, such as a cryogenic tank, where there is a change in diameter or radii at one end thereof, e.g., where the bottom of the tank curves inwardly to a disked-shaped bottom or top.  
  In general, the apparatus and process of the invention have been found to be entirely satisfactory for processing stationary elongate sheets while accommodating the strains and stresses encountered in the operation and minimizing the factory floor space required for the operation.  
  A typical sheet to be flanged in accordance with the invention will be a 304-type stainless steel sheet having an average thickness of about 0.02 inches. Such a material is elected primarily for its utility in making cryogenic tanks, i.e., for its ductility tensile strength, and corrosion resistance. However, as will be obvious to those skilled in the art, the process of the invention can be adapted for processing a wide range of metallic sheet materials. In making cylindrical tanks, it is common that the sheet be somewhat rounded rather than absolutely flat. The sheets processed by the apparatus are often arcuate in shape, say from 3 to 6 in magnitude of are when received in section normal to the long dimension thereof.  
 ILLUSTRATIVE EMBODIMENT OF THE INVENTION In this application and accompanying drawings are shown and described a preferred embodiment of the invention. Various alternatives and modifications thereof are suggested, but it is to be understood that these are not intended to be exhaustive and that other changes and modifications can bemade within the scope of the invention. The suggestions herein are selected and included for purposes of illustration in order that others skilled in the art will more fully understand the invention and the principles thereof and will be able to modify it and embody it in a variety of forms, each as may be best suited in the condition of a particular case.  
 IN THE DRAWINGS FIG. 1 is a plan view of the apparatus of the invention, showing two tracks mounted along the sheet holding platform and a pivoted clamping device at one end thereof.  
 FIG. 1A shows one sheet clamp means.  
  FIG. 2 shows, in elevation, a roller-bender assembly mounted on a track adjacent to the platform.  
  FIG. 3 shows, in perspective, a sequential rolling operation.  
  FIG. 4 is an elevation of a sheet trimmer used in the process of the invention.  
  FIG. 5 illustrates means for moving rails in relation to the platform, the roller-benders and the sheet being bent.  
  FIG. 6 is a perspective view illustrating utility of sheets formed according to the invention in the construction of cryogenic tanks.  
  FIG. 7 shows means for holding a sheet being processed.  
  FIG. 8 shows a perspective view of a flanged sheet formed according to the invention, including the integral lower floor portion of diminishing width and uncrimped, upstanding side-edge flanges.  
  Referring to FIG. 1, it is seen that a sheet-processing assembly comprises a sheet platform 17, two carrier rails 19 mounted adjacent each side of platform 17, and clamp means 29 and 23 mounted at each end of platform 17. At one end of each rail 19 is an arcuate rail section 25. The sheet to be processed on assembly 15 is not shown in FIG. 1. As seen in FIG. 1, rails 19 extend beyond platform 17 at both ends thereof to accommodate the required travel of processing equipment, described below, which is carried on the rail 19.  
 Clamp means 23, mounted adjacent arcuate rail sections 25 is illustrated in FIG. 1A. It comprises upper and lower clamp bars 27 and 29. These clamp bars are tightened about a metal sheet 31 by bolt-tightening means 33. The processing apparatus carried on the rails 19, and best seen in FIGS. 2 through 4, include roller-bending modules 35 and edge trimmer 37. Roller bending modules 35, as illustrated in FIG. 2, include a lower roller member 39 comprising a cylindrical section 41 and a truncated conical section 43. The circumference of the cylindrical section 41 is tangentially positioned with respect to a sheet 31 being held on platform 17. The sheet 31 is bent upwardly by being forced against conical section 43, and the angle with which section 43 is positioned with respect to the circumference of section 41 is a measure of the amount of bend applied to the sheet by the module 35 to form a flange 38. Bending pressure is applied by engagement of lower member 39 with an upper cylinder 45 mounted to engage cylindrical section 41 as the assembly is pulled along rail 19. The clearance between rolls 45 and 41 is preferably equal to the thickness of the sheet.  
  As seen in FIG. 1, a plurality of roller-bending modules 35 are mounted on a rail 19 and pulled along at, say, feet per minute by a winch 47 mounted on extension 48 of a rail 19. Each sequential roller-bending module 35 imparts a somewhat more severe bend to the edge of the sheet being formed. While three modules 35 are shown, preferably six are used in practice.  
  FIG. 4 also shows a metal trimming device 37 advantageously mounted between two roller-bending modules 35. Although the sheet is rough-trimmed before being placed into the apparatus, it has been found to be more desirable to have the finish trimming done between two roller-bending modules. There are a number of advantages to this feature in that the excess metal to be trimmed is present and can be engaged by the first module 35 to help in performing the bending action, but is trimmed off before it gets to a following module where it could interfere with a proper bending&#39;to the increased angular displacement.  
  FIG. 4 shows details of the trimmer assembly 37. The device comprises two shafts 53 journalled in bearings 55 for rotation. Each shaft 53 carries a roller 57. Rollers 57 are spaced with a roll cutter member 59 on the other shaft to admit, snugly fitted, the edge of metal sheet 31. The frictional engagement of the sheet between rollers 57 and adjacent roll cutter 59 causes the rotation of shafts 53 and of roll cutters 59 carried thereon. Opposing roll cutters are spaced to assure cutting action. The trimmer 37 is mounted in a housing 61 riding on track 19 and is interconnected with brackets (such as those shown at 63) to modules 35 and, consequently, integrated into a roller-bender assembly which is pulled along the length of the track on modulesupporting rollers by the action of winch 47.  
  In FIG. 1, it will be observed that there are a number of rows of receptors 67 spaced therealong. These are to receive hold-down clamps 69 which may be used for holding down that side of the sheet 31 which is not being processed. Use of such clamps are especially useful when sheets 31 vary markedly in width. Such a clamp 69 is seen in FIG. 7 and comprise a pin 71 inserted in receptor 67. Pin 71 restrains sheet 31 laterally while a hold-down dog 73 contacts the upper side of sheet 31 and holds it down against platform 17. Receptors 69 are advantageously connected to the support bracing 74 which supports platform 17.  
  As seen in FIGS. 2 and 5, minor lateral adjustments in positioning the rails are carried out by adjusting the lateral position of rails 19. These rails are supported on leg support brackets 75 which are slidingly supported on cross beams 83 (See FIG. 1). Positioning assemblers 77 comprise a stop lever 79 and a threaded positioning bolt 81. Assemblies 77 are so placed along rails 19 that the stop lever 79 can be positioned for engagement with the adjacent end of a lateral brace member, e.g., an l-beam 83 mounted on platform support legs 85.  
  FIG. 6 is a schematic diagram defining the type of tank which is made possible by use of sheets formed according to the invention. It is seen that the tank comprises a large number of flanged metal sheets 31 which form the sidewall 87 of tank 89. These sheets are not only bent radially to form part of the circumference of tank 89, but they are also bent inwardly to form a major part of the transition curve 91 to the bottom ring 93. Plates 31 are welded to this bottom ring.  
  Ring 93 is, in turn, welded to radially-arranged bottom plates 95 and these are, in turn, connected to a center ring 97 Flanges 38, formed according to the process of the invention, are so placed that they are bent inwardly.  
 When the interior edges of these flanges are welded together, the walls of adjacent flanges form a suitable expansion joint or diaphragm 101.  
  A consideration of the tank shown in FIG. 6 shows that a complex 3-dimensional curve is required for the sheet 31. Not only must it have an upper wall portion to curve around the major circumference of the tank, but it must have an integral. lower, floor portion 108 to curve inwardly at the bottom of the tank and, at the same position, it must conform to the diminishing width of the lower, flat surface, floor portion of the sheet. That manufacture of such a sheet is possible is, perhaps, within the ken of those skilled in the metal working art. However, applicants efficient method of manufacturing such asheet while minimizing mechanical working and residual stresses in the metal is believed to be a significant contribution to the art.  
  FIG. 8 illustrates a sheet 31 formed according to the invention. Upper flat surface, wall portion 103 forms part of the inner surface of tank 89. Flanges 38 bend upwardly and inwardly according to compound curve 105, along baseline 107 of the flange and are uncrimped as at 109 and 110 in the integral lower floor portion 108.  
  The upper wall portion 103 of sheet 31 is substantially flat in a predetermined plane to form the cylindrical side wall of the tank. Unlike a flanged stave of a conventional small metal barrel, wherein the lower end of the flanged stave is curved outwardly and free of flanges, the thin, approximately 30 feet long sheet body 31, has an integral lower end bent inwardly in a transition curve of gradually decreasing diameter as shown in FIG. 8. Thus the integral lower floor portion 108 terminates at a lower edge portion which is substantially horizontal to merge with a generally horizontal bottom ring 93. Also unlike a conventional, flanged, metal, barrel stave the upstanding flanges 38, are continuous from top to bottom of the body 31 including the transition curved portion 91 and terminal floor portion 103.  
  It is to he understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention which might be said to fall therebetween.  
 What is claimed is:  
  1. An elongated, relatively thin metal sheet adapted to form a liner section of an expansible wall and floor of a cryogenic tank, said sheet comprising:  
 an elongated body having an upper wall portion and an integral lower floor portion with an upstanding flange along each opposite longitudinal edge thereof, said flange being bent along a compound curved base line progressively and evenly with a roll bent appearance free of unwanted crimps and wrinkles,  
 said lower floor portion being bent inwardly out of the plane of said upper wall portion in a transition curve to a terminal lower edge portion substantially in a horizontal plane for merging with the floor of said tank,  
 said body being at least 30 feet long, 2 feet wide and of stainless steel and each said flange extending continuously the full length of both said longitudinal side edges, of said upper wall portion and said lower floor portion to a height of at least 2 inches, while being free of crimps, fractures or pleats.  
  2. A cryogenic tank formed of sheets as defined in claim 1, each said sheet having said continuous, full length edge flanges and having each said edge flange continuously welded to an adjacent similar edge flange of a juxtaposed said sheet including the flanges of said lower floor portions to permit expansion and contraction of the resulting expansion joint, or diaphram, without gas leakage.  
 3. An elongated sheet as specified in claim 1 wherein:  
 said sheet body diminishes in width from the said upper wall portion to the terminal edge portion of the said lower floor portion thereof.  
 4. An elongated sheet as specified in claim 1 wherein:  
 said lower floor portion is bent inwardly out of the plane of said upper wall portion in a transition curve of changing diameter.  
 5. An elongated sheet as specified in claim 1 wherein:  
 said transition curve progressively diminishes in diameter toward the lower edge portion of said lower floor portion.