US3362118A - Expansible surface structure - Google Patents

Description

Filed July 6, 1965 A. BRUNNER A. BRUNNER EXPANS I BLE SURFACE STRUCTURE Jan. 9, 1968 8 Sheets-Sheet 2 Filed July G, 1965 /n Ven for: HAFRED Rv/v/v 6R KTM/VNI? 75 Jan. 9, 1968 A. NNNNN ER 3,362,118

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EXPANSIBLE SURFACE STRUCTURE l Filed July 6, 1965 8 Sheets$heet G In Venor:

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A. BRUNNER Jan. 9, 1968 EXPANSIBLE SURFACE STRUCTURE 8 SheetSwSheet Filed July e, 1965 /n Vemor: A L FRED BRUN/veg /Qwm r /e/nwn Jan. 9, 1968 A. BRUNNER EXPANSIBLE SURFACE STRUCTURE 8 Sheets-Sheet 8 Filed July 6, 1965 /m/en for: ALFRED BRUN/vsn KW //yah United States Patent O 3,362,118 EXPANSIBLE SURFACE STRUCTURE Alfred Brunner, Winterthur, Switzerland, assignor to Sulzer` Brothers, Limited, Winterthur, Switzerland', a corporation of Switzerland Filed July 6, 196s, ser. No. 469,793 Claims priority, application Switzerland, July 6, 1964, 8,812/64 2 Claims. (Cl. 52-284) ABSTRACT OF THE DISCLOSURE The expansible structure is constructed of two expansible sheets which are connected to each other at a right angle by a plurality of triangularly shaped areas or trapezoida-l shaped areas. The sides of the triangularly or trapezoidal shaped connecting areas are joined to the terminal parallelogram shaped areas of each expansible sheet.

The invention pertains to an elastic geometric surfacing structure which is charcterized in that the structure is composed of a multiplicity of oblique-angular areas of parallelograms which are interconnected at their edges in such a manner that each parallelogram is inclined to a plane that is parallel to the stretchable surface structure as a whole. By virtue of this novel design the structure according to the invention distinguishes itself by an exceedingly high elasticity when subjected to stress. Thus, such a development is uniquely suited to be used as a structural support member in environments where momentary or periodic stresses are apt to occur. The invention relieves such momentary stresses by stretching or expanding, thereby avoiding a buildup of internal forces that are apt to lead to structural failure of materials in ordinary planar form. The structure returns to its normal at-rest configuration when the stress is removed, hence, it is deemed elastic Its use is especially advantageous as a structural element in locations where it is subject to wide temperature changes, for example in combustion charnbers of steam generators where it forms the inner skin casing for the tubing.

The structure of the invention, which, in use, is fixed at the edges, produces less stress by reason of local heating than a plane sheet would under identical conditions. The reason for this phenomenon stems from the slight erection of the surfaces of the particular arrangement of parallelograms making up the structure, so that they can increase or decrease their inclination towards the plane parallel to the body in response to stresses placed upon it.

Hence it is an object of this invention to provide a Structural element adapted to relieve forces applied to it by deforming when stress is applied.

It is an object of this invention to create a three-dimensional ,structural element which is adapted to yield in one direction when a force is applied thereto in another.

It is another object of this invention to provide a sheet composed of interconnecting planes forming a threedimensional element capable of being stretched or pulled without loss in strength.

It is yet a further object of the present invention to provide such a three-dimensional sheet of interconnecting planes wherein an expansion of the sheet in one direction causes a relief movement of equal magnitude in another direction.

Yet another object of the invention is to provide means for joining together two or more such three-dimensional sheets of interconnecting planes at angles, so as to form composite sheets adapted to contour with non-planar surfaces.

3,362,118 Patented Jan. 9, 1968 According to one kind of design of the invention, the structure is composed of a plurality of congruent areas of parallelogram-shaped areas held together along their edges. This forms a structure defined by right angles which has the advantage that it retains its right angles when it deforms, for example by being stretched. As a result it does not become a structure of obtuse angles. This form is discussed hereinafter with respect to FIG. 1.

Another advantageous form of design of the invention exists in providing interconnecting parallelogram surfaces whose connecting corners form two obtuse and two acute angles in each instance. This is discussed hereinafter With respect to FIG. 2. By this arrangement the advantage is obtained that an expansion exerted in one direction of the object develops a relieving expansion of the object in the transverse direction. This phenomenon may be modified so that the expansions in both of the directions respective to the unit of length are the same.

In a further form of this design of the invention the acute angles of the areas of the parallelograms of which the sheet is composed are about 60 and the inclinations of the ascending and descending edges towards the plane parallel to the whole sheet are about 45.

Two sheets of material made according to the invention can be joined tightly and integrally together in a simple manner at an angle by providing triangular or trapezoid areas between the planes of the parallelograms at the joint between them. Such a connection shows the same properties of deforming as the two structures held toget-her by it. Such constructions are discussed herein in connection with FIGS. 6-8.

If, in the embodiment discussed above, the triangular or the trapezoid areas have two acute angles which are the sarne as the acute angles of the areas of the parallelogram, there is created an especially suitable way of producing a corner connection between two expansible surface structures of equal stretchability. If one combines this characteristic of design with that according to which the acute angles of the parallelogram areas are about 60 and the inclinations of the ascending and descending edges towards the general plane of the sheet material are about 45, then one obtains a right-angled corner connection of two such surface structures which exhibits the same property of deformation as the connected structures.

The embodiments referred to above, and others, are more fully explained in the following description with the aid of the drawings, in which:

FIG. 1 shows in a perspective view an expansible sheet structure whose surface is composed of rhombs.

FIG. 2 shows in perspective view an expansible sheet structure whose surface is composed of rhomboids.

FIG. 3 shows a modified form of the embodiment of FIG. 2 in a perspective view.

FIG. 4 shows the form of the embodiment according to FIG. 3 in plan view and on a smaller scale.

FIG. 5 shows a section taken along line A-A of` FIG. 4.

FIG. 6 shows a perspective view of two expansible sheets which meet at right-angles.

FIG. 7 shows a modified form of the embodiment of FIG. 6.

FIG. 8 shows the form of the embodiment according to FIG. 7 from the opposite line of vision than in FIG. 7.

FIG. 9 shows a section through the wall of a combustion cham-ber of a steam generator which utilizes a structural element according to the invention.

According to FIG. 1 a plane panel of material, for instance of sheet metal, is formed into an expansible sheet structure 1 composed of congruent rhombs 3 bounded by e: edges 2. These congruent rhombs 3 are oblique-angled parallelogram surfaces the sides of which are equally long. A plane parallel to the expansible structure 1, i.e. the general plane of the sheet, is indicated by the dotted line 4. The rhombs 3 are inclined relative to this plane and arranged in such a manner that in each salient corner 5 formed by four rhombs, four acute angles meet, whereas at each saddle point 6 formed by the four rhombs and situated lower and between opposed salient corners 5, four obtuse angles meet. If one would observe the Whole sheet 1 in plan view the rhombs would appear as squares. The expansible sheet structure 1 has (if it is not fixed at its edges) the ability to contract in Y direction under the exertion of a pull in X direction, or vice-versa. Yet the distance between two planes which may be imagined to be lying through the upper and lower lying salient corners 5 of the structure 1 remains substantially constant in the effective expansional region of the structure. However, when the same structure has its edges fixed and is subjected to local heating, the distance between the two planes becomes somewhat larger.

It is also possible to compose the structure 1 of rhomboids instead of rhombs, whereby again four acute angles meet in each salient corner and four obtuse angles at each saddle point.

In the embodiment of FIG. 2, the expansible sheet structure or panel 7 is composed of congruent rhomboids 8, i.e. areas of parallelograms of oblique angles, the nonparallel sides of which are not equally long. The general plane of the panel, and to which the rhomboids 8 are inclined, is here indicated by a dotted line 11. In the case of this embodiment, two obtuse and two acute angles meet together at each protruding corner 9 formed by four rhomboids 8 as well as on each receding corner 10 formed by four rhomobids 8. This embodiment has no saddle points like those in the embodiment according to FIG. l; and instead of a plane extending through the upper-lying corners on points (as in FIG. 1), the embodiment of FIG. 2 has a tangent between the corresponding corners and a corresponding plane. Hence, the ridges interconnecting protruding and receding corners 9 and 10, respectively, all lie in the same plane. See FIG. 5. By virtue of the described design, panel 7 can expand in Y direction as well as the X direction in response to a pull exerted in the X direction.

In the embodiment shown in FIG. 3, non-parallel sides of the areas of the parallelogram are of a very different length as contrasted with the embodiment of FIG. .2. The FIG. 3 embodiment has the particular advantage that the expansible sheet 13 is more rigid and therefore is more suitable as a supporting structure. The areas of the parallelograms have acute angles of 60 and the obtuse angles are accordingly 120. This is illustrated in the plan view of FIG. 4 which shows an area of a parallelogram (indicated by a dotted line) when folded into the plane of the drawing. The inclination of the parallelogram-area relative to the general plane 14 of the structure 13 is 45; this is illustrated in FIG. 5. Through these angles of 60 and 45 the property is obtained through which the panel structure 13 expands in the X and Y direction the same unit of length as said structure is pulled in the X or Y direction.

FIG. 6 shows how the planes of an expansible panel 15 and an expansible panel 16 can be made to meet and join at an angle, such as the 90 indicated. Each structure 15, 16 is formed of rhomboids 19 of equal size within itself. The angular transition of the expansible structure 15 to the expansible structure 16 consists here of equilateral triangles 17, each of which may be considered as belonging half to structure 15 and half to structure 16. Edge 1S accordingly belongs to both stretchable structure 15 and 16, and the searn along this edge 18 tends to unfold when a pull is exerted in the Y direction. However, bccause of this edge 18 the connection cannot be compressed 4 in the Y direction out of the position as sketched in FIG 6.

A modified form of the embodiment of FIG. 6 is shown in FIG. 7. In the embodiment according to FIG. 7 a strip 20 of interconnecting trapezoids is furnished between the two expansible panel structures 15 and 16 in order to render possible such a compression. Hence, there is no edge like that of edge 18 in FIG. 6.

FIG. 8 shows the same form of embodiment as FIG. 7, but viewing it from the opposite side of the connection between expansible structures 15 and 16.

FIG. 9 shows how the structure according to the invention is used, for instance as a skin-casing in a furnace. That is, the extensible structure 21 of the invention is located as a skin-casing behind the tubing wall 22 of a combustion chamber of a steam generator. Tubing wall 22 consists of many spaced parallel pipes through which fluid flows, such pipes being exposed to external heat flow as symbolized by arrows 23. At the side of the expansible body 21 oppo-site that of the tubes 22 and spaced some distance therefrom is a tin sheeting 25 constituting the outer skin of the steam generator. The interspace between this sheet metal (tin sheeting) 25 and the structure 21 is filled with insulating material 24, for example mineral wool, If necessary there may be a provision for a thin anti-radiation sheeting (not shown) between the tubing wall 22 and the elastic surface body 21. The described construction of walls of combustion chambers is particularly advantageous for steam generators which are equipped for high-pressure firing.

In most applications the expansible surface structures of the invention generally need to be connected to or supported by structures having a plane surface. This is done, for instance, by connection strips in which the areas of the parallelograms gradually diminish toward the planesurface-structure so that this, in a way, results in tapering-off zone. At the point of interconnection the structure approaches a planar character as opposed to a three dimensional one.

The stretchable structures may be conveniently produced of metal by pressing in stages, or by deep drawing, or by making small linear recesses which are preferably not as deep as the metal sheet is thick and then folding or telescoping the sheet. The edges defining the areas of the parallelograms may be slightly rounded instead of sharp.

What I claim is:

1. An expansible structure comprising a pair of expansible sheet structures disposed at a right angle to each other to form a miter cut therebetween, each said expansible sheet structure including a plurality, of oblique-angled congruent parallelograms inclined to the plane of the structure, each adjacent four of said parallelograms 4being connected to each other on a pair of acute angles and a pair of obtuse angles to define a joint; and a plurality of triangularly shaped areas connecting said pair of expansible sheet structures, each said triangularly shaped area being disposed in opposition to another of said triangularly shaped areas, each pair of opposed triangularly shaped areas being secured to each other along a common edge thereof and to each of said expansible sheets, said triangularly shaped areas each having an apex disposed opposite said common edge outwardly of the expansible structure along a common line.

2. An expansible structure comprising a pair of expansible sheet structures disposed at a right angle to each other to form a miter cut therebetween, each said expansible sheet structure including a plurality of oblique-angled congruent parallelograms inclined to the plane of the structure, each adjacent four of said parallelograms being connected to each other on a pair of acute angles and a pair of obtuse angles to define a joint; and a strip connecting said expansible sheet structures together, said strip including a plurality of interconnected trapezoidally shaped areas, each said trapezoidally shaped area being disposed in opposition to another of said trapezoidally shaped areas, each pair of opposed trapezoidally shaped {2,963,128 12/ 1960 Rapp 52-630 X areas being secured to each other along one edge thereof, 3,184,094 5/ 1965 French et al 220-9 to each of said expansible sheets along other respective 3,313,080 4/ 1967 Gewiss 52-618 edges thereof and to an adjacent trapezoidally shaped FOR EIGN PATENTS area along the remaining edge thereof. 5

209,577 7/ 1957 Australia. References Cited 611,302 10/1948 Great Britain. UNITED STATES PATENTS HENRY C. SUTHERLAND, Primary Examiner. 2 @ggg @22 igtton 10 ALFRED C. PERHAM, Assistant Examiner.

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