Composite slab sheet or plate

Jan. 1, 1946,

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2,391,997

W. NOBLE

COMPOSITE SLAB SHEET OR PLATE

Filed March 26, 1942

Sheets-Sheet 1

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Jan. 1, 1946.

2,391,997

W. NOBLE

COMPOSITE SLAB SHEET OR PLATE

Filed March 26, 1942 3 Sheets-Sheet 2

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1946.

W. NOBLE

COMPOSITE SLAB. SHEET OH PLATE

2,391,997

Filed March 26, 1942 3 Sheets-Sheet 3

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Panyen JJpJbyLe,

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UNITED STATES PATENT OFFICE

Patented Jan. 1,1946

2,391,997

2,391,997

COMPOSITE SLAB SHEET OR PLATE

Warren Noble, Washington, D. C., assignor to Lilly Florence Shirley Noble, Garden City, N.Y.

Application March 26,1942, Serial No. 436,345

Claims. (Cl. 189—36)

This invention relates to a new article of manufacture in the form of a slab or plate of almost any formable substance composed of two thinner sheets or plates, one of which is smooth, the other so arranged as to surf ace as to act to space, δ stiffen and aid in joining the composite sheet to another or to an adjacent member. The purpose of the invention is economy; economy of material, of weight, of fabricating time and in the nature of the machinery of fabrication, of labor 1® and of heat necessary in making the joint and lastly by making possible structures of superior rigidity without encroachment upon space interior to the walls of the structure.

A plate so made will approximate the stiffness '⁸of a solid sheet of similar dimensions against some stresses and even exceed it in others, despite a weight ratio of solid to composite of not less than five to one. For some purposes this ratio may even be exceeded although the tensile “® strength of the composite sheet, as compared with the solid plate will remain in the approximate ratio of the areas of metal in the contrasted cross sections. Modem design, however, rarely needs to concern itself with strength per se. It seems ⁸invariably true that a structure sufficiently stiff for its purpose is strong enough under all its working conditions.

Costs of material and fabrication aside, light 30 structure has so infinite a scope in progressive design as to demand the utmost attention to its devisement, especially in the transportation fields. Material made under the instruction of this invention would substitute for solid section of simi- 35 lar depth, eliminate necessity for much auxiliary structure, yet maintain the low weight desirable both for better function and cost reduction.

Aerial craft daily advance in importance as a class of manufacture so any simplifying factor in 40 design is of interest.

Ship building, at the moment is seriously hampered by shortage of steel on the one hand and by the lack of facilities for fabricating heavy plate on the other. 4S

Our national facilities, however, have been of late years vastly expanded as to light gauge sheet and a surplus of machines for fabricating light gauge metal actually exists without prospect of employment in the present situation. ⁵⁰

While ship construction based on composite plate of this type would be unconventional it might be helpful in enabling existing machine equipment to manipulate vital material to a vital purpose at less cost, with less material, with less ⁸⁵ energy, human and otherwise and with a more competent end result.

While the initial statement of this application “this invention relates to a new article of manu5 facture” is technically correct it would be equally true to say it outlines a design system whereby simple structures may be quickly made with a minimum of material and energy.

In the accompanying drawings:

Figure 1 is a perspective, sectional view of one form of the invention.

Figure 2 is a perspective view of an adjoining strip.

Figure 3 is a section on line 3—3 of Figure 2. 15 Figure 4 is a section on line 4—4 of Figure 2.

Figure 5 is a sectional view showing the manner of joining two elements of the type shown in Figure 1.

Figure 6 is a perspective, sectional detail.

Figure 7 is a plan view of a modified form of the invention.

Figure 8 is a section on line 8—8 of Figure 7.

Figure 9 is a plan view, with certain parts broken away, showing another modification.

Figure 10 is a section on line 10—ί 0 of Figure 9.

Figures 11,12 and 13 are sectional views of further modifications.

Figure 14 is a sectional view, illustrating one method of securing a structural element to the ³⁰ article of the present invention.

Figures 15 and 16 are plan and sectional views of another modification.

Figure 17 is a sectional view of a modified form of joint between two adjacent sections, and ³⁵ Figure 18 is a diagrammatic view showing a preferred method of welding adjacent sections.

In a preferred form of fabrication, two sheets of material 10, i I of similar dimensions and character are taken. One sheet 10 is left smooth, the ⁴⁰ other embossed, as at 12 to suitable depth and pattern to provide the desired thickness of the composite plate when superimposed upon the smooth sheet. The two are then welded together at the points of contact 13, becoming a single unit which ⁴⁵ thereafter may be treated precisely as a solid sheet might be. The weld 13 may be a zone of spot welding in the form of a series of circumferential spots around the opening i 4, formed, for instance, by a series of projections, or the weld 13 may be ⁵⁰ a continuous line formed by a hollow cylindrical electrode welding around the periphery of the opening 14. To become specific for the sake of clarity let us take two similar sheets of steel of a thickness easily produced by a continuous rolling ⁸⁵ mill, leave one sheet alone but on six inch centres

2,301,097 in staggered but symmetrical arrangement pierce half inch holes 14 and draw down angularly walled cups 15—like patty pans—from the zone surrounding each hole, the depth or the cup to depend upon the final thickness of assembly desired. Such pans or depressions 15 can be drawn down, where a central hole 14 exists, without materially distorting the surrounding metal so the exterior dimensions will not be affected and the two sheets can be superimposed with edge parallel 10 to edge. The welding 13 takes place about the pierced bottom of each patty pan 15, by any of the methods suggested above.

While Joints may be fewer in a structure built from this composite sheet since longer lengths of 15 thin material can be rolled, handled and welded together than possible with the heavy solid plate the joining of composite sheets in a manner to assure fluid tightness and at the same time avoid weakness at the joint is part of the problem and 20 of this invention. One method, as indicated in Figures 2-6, employs a backing strip 20 for the interstice formed between the sizes or shapes as laid up, the depressions or pans (6 in the embossed sheet being divided in halves along the 25 border zones, these halves lacking depth as compared with the other depressions 15 in the sheet area by the thickness of the metal of the backing strips 20 in order to nest in reinforcing pockets 21 in the strip, similar in all form respects to the SO embossments (5—10 used on the stay sheet except for an interpocket channelling 22. Thus the backing strip presents a continuous smooth surface when in place immediately behind and in contact with the smooth surfaces while the pockets 35 2t in the strip embrace the half embossments 16 left at the edges drawing them tight together.

Projection welding spots 23 are formed at the mouth of these pockets and along the flange 24 of the channel portions. These spots may be in 40 the form of fine edged rings 23 swaged by pressure from the neighboring metal. By the use of suitable electrodes it is possible to weld the backing strips 20 to the embossed sheet 11 at the projection welding spots 23 and to weld the smooth 45 sheet joint between sheets and to the face 25 of the backing strip channel portions 22, securing a smooth joint for the outer face or skin (0 of the structure and ample reinforcement for the embossed face, notwithstanding the fact that the 50 backing strip 20 is completely enclosed within the walls of the composite elements. Projections similar to those shown at 23 may be employed at the contact surfaces of the sheets to be joined. The smooth plates (0 and the embossed plates welded with their ends butted at the lines of division contact.

Apart from the direct economy of primary material the use of light sections of metal aid the welding characteristics making for speed and the 60 use of less electric current or gas. The backing strip helps in making welds and at no time does spot welding have to be attempted through double thickness. The embracement of the half cups 16 by the double thickness backing strip relieves the 65 weld of much of any strain which may later be imposed and assures the true positioning of adjacent plates each to each prior to welding.

It is not essential for facing and backing sheets to be similar in gauge or analysis. Dissimilar 70 thicknesses and analyses may be used in accordance with ordinary welding practice. Thus a stainless steel may be used for the smooth surface It matched with a cheaper grade for the stay sheet II. 7«

II are 55 nel.

It should be observed the shallow edge cups may be halved along the edge of a plate or quartered, as at (6', at the comers, and it is important in order that the reinforcement may be at its full 5 value for these divisions to be accurate. In special cases it may be advisable to use cups alone without attached channels to complete the joint, inserting the channels separately. The centre spacings of embossments used should in any case be accurate within ordinary precision limits and it may be found useful, for some service to carry indications of the centres through the smooth plate so a gun welder may be properly located from the smooth side.

In forming the joint of the type shown in Figure 5, a pair of composite plates of the type shown in Figure 1 are first prefabricated, by welding the embossments 15 to the smooth sheets 10, along lines 13, but leaving the bottoms of the embossments (6 and 16' spaced from the sheet 10 as Indicated at 21, a distance equal to the thickness of the metal in the channel member 20. Because of the inherent spring of the metal in the composite plates, the sheets 10 and 11 may be separated slightly along their edges and the channel member 20 inserted by a combined sidewise and rotational movement about its longitudinal axis so that the edge embossments 16 and 16' are positioned within the pockets 21 of the backing strip 20. The next plate may then be joined by similarly spreading the plates 10 and It along their edges and positioning the half-embossments within the unoccupied halves of the pockets 21.

The dimension of the spaces 27 between the bottoms of the half or quarter embossments 16 and 16' is such that the bottom 25 of the jointing cups 21 are pinched between the smooth plates and the embossments, under the inherent springiness of the metal. Also, the projections 23 somewhat spread apart the embossed sheets and the smooth sheets which subjects the projections to the spring pressure of the metal.

This spring contact is most useful in following up the weld when welding current raises the projections 23 to welding heat, which occurs after the parts have been assembled as just described.

In forming the welded joint between the composite plates assembled in this manner, a central electrode contacts the bottom 25 of the channel 2· through the opening at the center of the half or quarter embossments, as well as the periphery of the embossments 16, 16'. Heavy spring followup is preferably used to assure ample pressure at the projections and along the flanges of the chanThis operation may leave the edges of the smooth plates (0 slightly apart, but in firm contact against the bottom surface 25 of the channel. Thereafter, these edges are electrically or otherwise welded together to secure fluid tightness and to anchor the edges of the plates I· to the surface 25 of the strip. Being of light gauge, the metal is swiftly brought to welding temperature and a completely supported joint is made.

It will be understood that, when the composite plates are assembled, a pair of adjacent quarter embossments 16' at the comers will be disposed adjacent to each other and preferably opposite to a half embossment IB on the edge of the next composite plate so that the lines of junction between the plates may be staggered and discontinuous.

For some purposes the flat bottomed, pierced cup can be replaced by a single conical embossment as Indicated at 36 in Figures 7 and 8, the apex 31 of the cone becoming a projection spot.

2,391,1

This is especially desirable where very thin metal is to be used and where the depth of the section is small, and also in some bends where close pitched reinforcement is desirable. Pitch and centre distances of embossments are entirely a 5 matter of material and conditions.

There is merit in double welding, i. e. along both inner and outer sheet junctions but the process is slower and in the main the seam weld along the inner seam Is unnecessary. 10

The shot welding of the reinforcing cups should in any case be retained.

Sections of composite sheet may have other than parallel sides. For example as indicated in Fig. 11 a tapered wing might be built by using 16 graded depths and pitches for the embossments. Sections having more than two plane surfaces may similarly be constructed.

In general the embossment in the form of a truncated right cone having a circular base will 20 be found completely adequate but special conditions may arise wherein an elliptically based embossment, as indicated at 40, 41 in Figures 15 and 16 will prove advantageous in searching for the ultimate economy of weight. 25

Staggered pitch in symmetrical pattern may be less efficient than a pitch arrangement patterned to meet the loading conditions. Stepped overall thickness may have place In transition of zones of section. Such matters are in the 30 province of design and in no way depart from the spirit of the invention.

Figures 7 and 8 illustrate an unpierced cone type of embossment in which the apex 31 of the cone 30—being thinned in the draw provides its own welding projection.

Figures 9 and 10 indicate the method of using double embossment to produce a double faced smooth plate.

Smooth plates 33, 34 are welded to the ends of downwardly and upwardly projecting cones 35, 36, respectively, pressed from the intermediate embossed sheet 37, the latter acting as a stiffening member for the two smooth plates. As indicated in Figure d, the cones are preferably staggered, but any other arrangement may be adapted, depending upon the use to which the composite plate is to be put.

In Figure 11 a diagrammatic representation of a tapered structure is given showing change in depth and pitch of the cups 38 both as demanded by optimum design considerations and by the practical conditions governing the relation of diameter to depth of draw. A curved surface is represented by Figure 13. Its purpose is to indicate the use of chordal flats 45 between the pitch of the embossments 46. This advantage in stability comes from delaying the welding operation until after the desired bend in the smooth plate is established. While Figure 13 shows cones for embossments, the spherical embossment 47 shown in Figure 13 are often preferred. Moreover the spherical embossments are of particular utility in tapered sections, as shown in Figures 11 and 12.

The advantages of the use of the present invention in connection with the curved sections will be apparent when consideration is given to the difficulties encountered in bending solid plates of substantial thickness. Operations of this type require heavy machine tools and the expenditure of considerable power. With a composite sheet in accordance with the present invention, similar results may be accomplished quite readily by bending each of the elements of the plate, before the sealing operation is performed. The result >97 3 ing product is exceptionally stable and stiff, since the chordal sections or flats 45 act as straight brace members and restrain bending.

The tapered composite plate, as indicated in Figures 11 and 12 has numerous advantages over corresponding solid plates, particularly from the point of view of initial manufacture, since it is a difficult task to roll out or machine down a solid plate to a variable thickness.

Figure 14 Indicates a preferred method of attaching a composite sheet to structural members, such as bulb angles and the like. The embossed plate H' is apertured at 50, 51 for the reception of clamping bolt assemblies 52 and for the foot electrode 53 of a welding apparatus, the upper electrode 54 being positioned to engage the flange 55 of the bulb angle.

Figures 17 and 18 illustrate modified joints between adjacent composite plates. The smooth plates 10a have their margins turned upwardly as indicated at 57. The embossed plates I la have their marginal portions 58 disposed on downwardly inclined planes and their edges 59 turned upwardly, thereby providing marginal channels 60 for the reception of roller electrodes 61, 62, adapted to function in the manner fully described in my co-pendlng application for patent, Serial Number 388,853. Welding current flows from one electrode through the upturned edge 59 of the embossed plate, through the two flanges of the smooth plates 10a, then through the other edge 59 and finally to the other electrode. Since the metal Is relatively thin, the roller electrodes 61,62 may be moved along the joint quite rapidly, 35 to provide a continuous welded seam.

If desired, the opposite, smooth face may be welded, as Indicated at 63.

The flanges 57 of the smooth plates 10a may extend a substantial distance beyond the em⁴⁰ bossed plates, as indicated at 64, to serve as a reinforcement.

In some cases It may be desirable to reinforce the smooth skin sheet against local puncture. This can be done by filling the space between the sheets with a setting compound, including cement or plaster. The filler may be inserted in unit form or poured in plastic condition. Preferably, however, jointings are left free of compound so that the back strip can be inserted and the ⁶⁰ welding operations performed. In some cases, the plastic material can be inserted after the whole structure is completed. Resonance is greatly reduced by the use of such material, and the sound-proofing qualities greatly increased.

⁸⁵ While this specification deals with a single plate and its relation to adjacent plates or other members and so defines a unit of construction the development of the system opens up fields of design hitherto untouched.

It would for instance be feasible and economical to fabricate a ship’s hull in such a manner with only a minimum of other framing, since the general stiffness and resistance to torsion would approximate that to be expected If plates of sim⁶⁵ ilar solid thickness were to be employed. Thus a wall depth of say three inches using 11 gauge plate would only weigh the same as the same area of Ά inch solid plate—a thickness much too light to be used without close framing· The total ⁷⁰ weight of such a hull would approximate onefourth of that of normal conventional construction, and fabrication facilities could be found almost anywhere in the U. S. A. Production of suitable sheets could be effected on continuous ⁷⁶ mills and the handling would be lighter so avoid2,381,987 ing much of the difficulty of cranage supply. For equivalent lines the effective hull space would be much greater.

In aircraft work avoidance of the myriad rivet holes would make for simpler, cheaper and more 5 aerodynamically efficient general arrangements of plane elements.

The cost of composite plate is almost directly as the weight if material alone is considered, since the fabricating cost of the embossed mem- 10 ber is very small with proper equipment. If handling machine overheads and assembly welding are included the potential saving over solid metal is large. Contrasted with equivalent structure characteristics obtained with solid plate and con- 15 tributary framing the economy is striking.

Hie use of the terms “weld” and “welding” used throughout this specification must not be taken to preclude the use of other methods of firm attachment under other circumstances and with 20 other materials. Thus brazing in controlled atmosphere furnaces would be satisfactory so far as the junction between the plates is concerned, equally so silver soldering with or without atmosphere control. With non-ferrous metals, soft ₂s soldering would be adequate for many purposes. Even castings cored between surfaces to achieve the generic form of spaced plates connected by a multiplicity of right cones would provide the stiffness aimed at with economy of weight. 30

Although the invention has been described with considerable particularity, it must be understood that it is not limited to the details of construction described above and shown in the accompanying drawings, but Includes all modifications coming 35 within the scope of the appended claims and their equivalents.