US3672022A

US3672022A - Wire core structure for sandwich material

Info

Publication number: US3672022A
Application number: US811945A
Authority: US
Inventors: Charles Herbert-Greer York
Original assignee: WIRE CORE DEV CORP
Current assignee: WIRE CORE DEV CORP
Priority date: 1969-04-01
Filing date: 1969-04-01
Publication date: 1972-06-27
Anticipated expiration: 1989-06-27

Abstract

A wire core structure for sandwich material including a plurality of planar wire core ribbons which are formed of wire bent at right angles to form anchor sections on opposite sides of the core to engage the face sheets of the sandwich material-said core anchor sections being joined by joinder sections which extend at a right angle to the plane of the core structure. A notch is provided on the outside of some anchor sections to receive a cross wire extending in the plane of said core structure at a right angle to said core ribbons. Such notches are related to the diameter of said cross wires so that the cross wires will project slightly beyond the notch into which is received the cross wire, which spacing provides space for an adhesive, and yet, the cross wires may be deformed enough in welding to make the outer side of the cross wires generally flush with the outer sides of the anchor sections. In one embodiment there is a core ribbon which is serpentine and in one embodiment the ribbons are used in pairs which are offset to form a series of closed sections and a series of downwardly open sections and a series of upwardly open sections with a series of cross wires being received into said last mentioned downwardly open and upwardly open sections.

Description

United States Patent York 1 1 June 27, 1972 [541 WIRE CORE STRUCTURE FOR SANDWICH MATERIAL Charles Herbert-Greer York, Costa Mesa, Calif.

[73] Assignee: Wire Core Development Corp.

[22] Filed: April 1, 1969 [21] Appl. No.: 811,945

[72] Inventor:

Primary Examiner-Allen B. Curtis Attorney-Noel G. Conway [57] ABSTRACT A wire core structure for sandwich material including a plurality of planar wire core ribbons which are formed of wire bent at right angles to form anchor sections on opposite sides of the core to engage the face sheets of the sandwich materialsaid core anchor sections being joined by joinder sections which extend at a right angle to the plane of the core structure. A notch is provided on the outside of some anchor sections to receive a cross wire extending in the plane of said core structure at a right angle to said core ribbons. Such notches are related to the diameter of said cross wires so that the cross wires will project slightly beyond the notch into which is received the cross wire, which spacing provides space for an adhesive, and yet, the cross wires may be deformed enough in welding to make the outer side of the cross wires generally flush with the outer sides of the anchor sections. In one embodiment there is a core ribbon which is serpentine and in one embodiment the ribbons are used in pairs which are offset to form a series of closed sections and a series of downwardly open sections and a series of upwardly open sections with a series of cross wires being received into said last mentioned downwardly open and upwardly open sections.

5 Claims, 13 Drawing Figures WIRE CORE STRUCTURE FOR SANDWICH MATERIAL This invention relates to core structure for sandwich material, and more particularly to such core structure constructed of wire which has been bent and then joined together in order to provide the rigid low density core desired in sandwich materia1.

The present invention is used in sandwich material to provide a core structure of very light weight and yet very rigid construction. This core structure lies in a plane and has a face sheet joined to either side of the core material by means such as adhesive, or welding. Core structure has been previously constructed for sandwich structure, however, such core material has had the disadvantage of expense of manufacture and quality control.

Solely for purposes of establishing a frame of reference to relate together more easily the various components being described in this specification and the appended claims, the core structure will be described in terms of being placed in a position where the plane of the core structure forms a horizontal plane. The terms upper and lower, and upwardly and downwardly", above", and below, are used herein solely for purposes of relating the various components together and are not to be deemed lirnitive of the invention except as they relate the components together.

One principal aspect of the present invention is that it uses low cost wire material to form a series of core ribbons which are bent at right angles so as to look quite similar to a square wave. in the above mentioned horizontal orientation, these core ribbons have upper and lower anchor sections which extend generally parallel to the plane of the core material, and joinder sections extending perpendicular to the plane of the core material and joining the-adjacent ones of the anchor section. This reduces the length of the joinder section, and thereby increases their ability (for any given diameter or structural strength) to resist forces tending to crush the face sheets of the sandwich material together. Additionally, the

anchor sections are made sufficiently long that there is excellent area for adhesion between the said anchor sections and the face sheets.

Another aspect of the present invention is that the anchor sections of the core ribbons are provided with ofi'set sections at approximately the mid-portion thereof, which offset sections form notches to receive cross wires of the core material, which cross wires extend at a right angle to the core ribbons and serve to join together adjacent parallel core ribbons. Thereby, the core ribbons are held in their desired orientation for purposes of fabrication of the sandwich material. And, after the sandwich material has been constructed, the cross wires assist in holding the core ribbons against motion relative to each other.

These notches are provided by offsetting a portion of the anchor section inward toward the center line of the core ribbon, and therefore, the center of the resultant core structure. Thereby, the notch is provided on the outer side of the anchor section which outer side is at a position to be engaged by, or juxtaposed to a face sheet when the resultant sandwich material is constructed.

Another aspect of the present invention is that said notches in the anchor sections have an efiective depth which is slightly less than the diameter of the cross wires. The term "efiective depth as used herein means the distance that a cross wire is received in the notch. In measurement, a straight edge is placed across the particular anchor section on the outer side of the anchor section on which the notch is formed, i.e., the face sheet side of the anchor section.

This wire material has the advantages that the wire is readily available at comparatively low cost in a wide range of materials and sizes to provide a wide selection of strengths and characteristics in the final core structure. Further, the desired shapes can be constructed at very low cost. Further, the present core structure has the advantage that-as compared to, e.g., honeycombed core material, it has very few areas where the component elements of the core structure are joined together (and therefore, fewer areas for imperfect fabrication). And, the wire material is of such size that it can be easily, economically, and very reliably joined together by means such as welding.

Another aspect of the present invention is that resultant structure tends to the paths for conducting heat from one face sheet to the other. This aspect of the invention is particularly useful in areas such as high speed aircraft.

Another aspect of the present invention is that there may be included between adjacent ones of the above described core ribbons, a core ribbon wherein the core ribbon is made in a serpentine shape and the joinder sections extend diagonally between anchor sections which are little longer than the width of the notches formed therein. Such structure has the advantage that the last mentioned core ribbons will assist in thwaru'ng lateral movement of the face sheets relative to each other in the plane of such core ribbons.

Another major aspect of the present invention is that there can be provided core ribbons which are used in pairs laying along side each other. And, by offsetting said ribbons, there can be formed a resultant ribbon with a series of closed sections with upwardly and downwardly open sections alternately interspaced between adjacent ones of said closed sections. Then, by arranging such resultant box beam ribbons with said upwardly open sections in line and said downwardly open sections in line, the cross wires may be rapidly assembled for purposes of providing the desired core structure.

With the foregoing in mind, it is a major object of this invention to provide a new low cost core structure fabricated of wire material.

A further object of this invention is to provide wire core structure having extra strength with joinder sections extending at a right angle to the plane of the core structure.

It is still another object of this invention to provide a core structure wherein the core structure may be more securely secured to the face sheets of the sandwich material in which the core structure is used. 7

It is a still further object of this invention to provide an improved core structure having means for spacing core ribbons in the structure slightly away from the face sheets of the sandwich material with which the core structure is used in order to permit an adhesive to cover the entire area between the core ribbon anchor sections and the face sheet of the sandwich structure.

A further object of this invention is to provide an improved core structure having anchor sections of increased length in order to maximize the area for joinder of the core ribbons of the core structure to the face sheet of the sandwich structure.

It is still another object of this invention to provide a core structure wherein the component parts of the core structure may be more reliably joined together.

It is a still further object of this invention to provide a wire core structure wherein the core ribbons are so arranged as to provide a series of closed sections which may be aligned to form effective box beams in the core structure for additional strength in one direction of the core structure.

Another object of this invention is to provide an improved sandwich material resulting from the use of an improved core structure. s

A further object of this invention is to provide an improved core structure wherein the heat transfer through the core structure is minimized.

A still further object of this invention to provide an improved core structure having anchor' sections with notches formed therein for receiving cross wires of the core structure, which notches augment the securing of the cross wires to the core ribbons.

Still another object of this invention is to provide an improved core ribbon which may be manufactured in many dif ferent modified forms of the basic structure with little cost and adjustment in the machine making the core ribbon.

Other and furtherobjects of the invention will become ap parent in the detailed description below in connection with the attached drawings wherein:

FIG. 1 is a perspective view of a first preferred form which may be taken by wire core structure incorporating principles of the present invention;

FIG. 2 is a somewhat enlarged fragmentary elevation view disclosing some further details of the wire core ribbon used in the core structure shown in FIG. 1;

FIG. 3 is a further enlarged fragmentary view disclosing detail of the manner in which the effective depth of a notch on an anchor section of the core ribbon is related to the diameter of a cross wire of the core structure;

FIG. 4 is an enlarged fragmentary view showing details in the deformation of a cross wire cross section after the process of joining the core ribbon to a cross wire by a welding process;

FIG. 5 is an enlarged fragmentary view disclosing in further detail the manner in which a cross wire will act as a spacer between an anchor section of a core ribbon and a face sheet;

FIG. 6 is a perspective view of a second preferred form which may be taken by wire core structure incorporating principles of the present invention, which wire core structure includes wire core ribbons like in the first embodiment but with the core ribbons being alternately offset with respect to each other;

FIG. 7 is a somewhat enlarged elevational view of a second preferred form that may be taken by a wire core ribbon incorporating principles of the present invention;

FIG. 8 is a perspective view of a third preferred form which may be taken by wire core structure incorporating principles of the present invention;

FIG. 9 is an enlarged fragmentary elevational view of a third preferred form that may be taken by a wire core ribbon incorporating principles of the present invention;

FIG. 10 is a plan view of a fourth preferred form which may be taken by wire core structure incorporating principles of the present invention, which core structure incorporates the wire core ribbon shown in FIG. 9;

FIG. 1 1 is a fragmentary core sectional view of the wire core structure shown in FIG. 10, taken along line 11-11 in said Fig.;

FIG. 12 is a plan view of a fifth preferred form which may be taken by wire core structure incorporating principles of the present invention; and,

FIG. 13 is a cross sectional view of the core structure shown in FIG. 12, taken along line 13-13 in said Fig.

Referring now to FIGS. 1 to 5, there will be described a first preferred form which may be taken by wire core structure incorporating principles of the present invention. In FIG. 1, there is shown such a first preferred form on the wire core structure, indicated generally by the arrow 10, which core structure is shown lying in a horizontal plane with an upper face sheet 11 on the upper side of the core structure and a lower face sheet 12 on the lower side of the core structure. Said face sheets 1 1 and 12 are secured to the core structure 10 by some desired means. The core structure 10 comprises a set of first core ribbons 15a-c which extend parallel to each other and lie in a plane which is at a right angle to the plane of the core structure. Each of these core ribbons are substantially identical. Accordingly, they have been given the same numeral designation with the difference being indicated by a letter. Each of the wire core ribbons 15a-c include a series of upper anchor sections 16a-c, and a series of lower anchor sections 17a-c which extend generally in the plane of the core structure 10. These anchor sections 16a-c and l7a-c are joined together in said core ribbons lSa-c by spacer sections 18ac. For purposes of structural quality, it is preferred that the joinder sections 18a-c are substantially the same length as the anchor sections 16a-c and 1711-0. Accordingly, as can be seen, the wire core ribbons 15a-c are formed with the wire being bent at right angles in order to form structure which looks much like a square wave. This serves to maximize the area which is available for securing the anchor sections 16a-c and 17a-c to the face sheets 1 l and 12 respectively, and serves to minimize the length of the joinder sections l8a-c. It will also be noted that each of the core ribbons 150-0 lie in a plane which is at a right angle to the plane of the core structure 10, i.e., with the upper anchor sections 16a-c respectively in line with the lower anchor sections l7ac. Also, the anchor sections -0 and 17H are spaced apart equally.

For purposes which will be described, there is provided in each of the anchor sections l6ac and 17a-c means for assisting in the securing of the cross wires to the core ribbons 15H. Referring now to FIGS. 2 and 3 which disclose details of the core ribbon 15a, it can be seen that each upper anchor section 16a has an offset portion 200 offset toward the center of core ribbon in order to provide a notch 21a on the outer side of the anchor section. At such position it faces the face sheet 1 1. Each such notch, as notch 21a, serves during the manufacture of the core structure 10 to index cross wires. As can be seen in FIG. 1, upper cross wires 23a-d extend parallel to each other in the plane of the core structure 10, and at a right angle to the various core ribbons 15a-c. Each of these cross wires 23a-d are received in a corresponding notch 21a on a corresponding anchor section 16a.

As in the case of the upper anchor sections 16a-c, the lower anchor sections 17ac are deformed toward the center of the core structure as at 25a-c in order to provide notches on the outer side facing the face sheet 12.

In FIG. 2 which shows the core ribbon 150, it can be seen that offset 25a provides a notch 260 on the bottom side of each anchor section 17a, which bottom side would be the outer side of the anchor section.

Referring now to FIGS. 2 and 3, the qualities of the notches will be described in further detail as related to a particular notch 21a in one of the upper anchor sections 16a. As can be seen, it is preferred that the offset portion 20a be approximately mid-way of the length of the anchor section 16a in order to divide the said anchor section into a left portion 29a and a right portion 30a. It will also be noted that the effective depth of the notch 21a is such that the cross wire 23 projects above the upper side of the anchor section 16a by a distance indicated by dimension arrows 28. The term effective depth" as used herein has relation to the distance into the particular notch that a particular cross wire will extend as measured from the outer side of the anchor section.

In practice, the notches are oftentimes not formed in the anchor sections as nicely as shown in said FIG. 3. More particularly, many times the

portions

29a and 30a are joined to the oflset portion 28 by a section of greater curvature than those shown in said FIG. 3. Because of this, the term effective depth" of the notch is meant that the depth which the cross wire can extend into the particular notch which depth is measured from a straight line extending across the outer side of the anchor sections. In other words, the distance which would be measured if a straight edge were laid across the outer side of the anchor section (which straight edge would be uneffected by any curvature occurring in the anchor section) and then measuring the amount of the cross diameter of the cross wire which extends into the notch from such straight edge.

One primary means of joining the cross wires 23a-d and 27a-d to the core ribbons is that of welding. Referring now to FIG. 4, the manner of joining one of the cross wires to an upper anchor section 16a will now be described. The weld is accomplished by applying pressure electrodes on the top side of the cross wire into the bottom of the offset portion 200. This causes the cross wire to deform during the heat of the weld process, and take on a resulting cross section which looks like weld cross section 31 which fills the notch. Preferably, the upper edge of the weld section 31 is flush with the upper or outer edge 32a of the anchor section 16a. In those cases where the notch is not formed as sharply as shown, and there is additional curvature between the offset portion (e.g., 20a) and the lefi and right hand portions (e.g., 29a and 30a) of an anchor section (e.g., 16a) the weld cross section 31 would not take on the substantially triangular cross section shown if FIG. 4. Rather, there would only be partial deformation of the cross section of the wire core. However, it is preferred-even in such latter mentioned casesthat the outer side of the cross wire be flush with a straight line extending across the outer edge of the corresponding anchor section, or project beyond said'line a desired amount. If the face sheets 11 and 12 are going to be welded to the core structure 10, it would be preferred that the cross wires be flush with such straight line across the outer side of the anchor section. If the face sheets 11 and 12 are going to be connected to the core structure by means of brazing, or adhesive, it is preferred that the cross wire project beyond such last mentioned straight line approximately one-eighth of the diameter of the cross wire.

Referring now to FIG. 5, there is shown details of the manner of connecting the core structure to the upper face sheet 11 by means of adhesive. In this Fig, it can be seen that the effective depth of the notch 21a is such that the cross wire 23c projects beyond the outer side of the anchor section 164.

Preferably, this is approximately one-eighth of the diameter of the cross wire 23c. Therefore, the face sheet 11 is spaced slightly away from the anchor section 16a. This slight spacing is desired in order that an adhesive 34 can cover the entire area between the face sheet 11 and the anchor section 16a. The thickness of the adhesive 34 (as demonstrated by dimension arrows 35) is greatly exaggerated in FIG. 5. The cross wires may be joined to the core ribbons by means of welding. Or, if desired, the cross wires may also be held to the respective anchor sections by means of adhesive. In such latter case, it would be preferred that the cross wires be adhesively bonded to the core ribbons in order to form a core structure which will maintain the proper relationship between its components during the adhesion of the face sheets to the core structure.

Referring now to FIG. 6, there is shown a second preferred form which may be taken by wire core structure incorporating principles of the present invention. In said FIG. 6, there is shown a wire core structure, indicated generally by the arrow 35, located between upper and

lower face sheets

36 and 37 respectively, to which the core structure is secured by some desired means. The core structure 35 is made of exactly the same components as the core structure 10 except that the wire core ribbons have been alternately ofiset. More particularly, the core structure 35 includes a plurality, or set, of first core ribbons 40a-b which are just like the core ribbons a-c and are positioned in parallel, equidistant relation. Such first core ribbons 40a-b include upper anchor sections, 4la-b respectively, and lower anchor sections, 42ab respectively. Additionally, offset portions 44a-b in the upper anchor sections, 4la-b respectively, and the lower offset portions, 45a-b respectively, in the lower anchor sections, 42ab respectively are provided to supply notches. for the purposes described above in relation to the wire core ribbons 15a-c.

The core structure 35 also includes a set of second core ribbons 46ab, and are positioned in parallel, equidistant relation. More particularly, the set of second core ribbons 46ab, include upper anchor sections, 47a-b respectively, and lower anchor sections, 48a-b respectively, each lying in the plane of the core structure 35, and each including ofiset portions, 49a-b respectively and 50a respectively. Joinder sections Sla-b join the upper anchor sections, 47a-b respectively, and the lower anchor sections, 48ab, respectively.

Extending across the top side of the core structure 35 are a plurality of upper cross wires 53a-g which are received in the corresponding notches in the upper anchor sections 41a-b of the first core ribbons, 40a-b respectively and the upper anchor sections 47a-b of the second core ribbons, 46a-b respectively. As can be seen, the second core ribbons 46a-b are offset from the first core ribbons 400-!) a distance equal to the length of an anchor section. Accordingly, each of the upper cross wires 53a-g is only secured to every other core ribbon. More particularly, upper cross wires 53b, d, and fare connected to the upper anchor sections 4la-b of the second core ribbons, 460-!) respectively. Positioned between the core ribbons 40a-b and 46a-b, and the lower face sheet 37, there are provided a series of lower cross wires 54a-g. Individual ones of these cross wires 54a-g are directly below corresponding individual ones of the upper cross wires 530-3. For the same reason as mentioned in connection with the upper cross wires 530- every other lower cross wire, to wit, lower cross core structure 35 as in the core structure 10. Although this does add to the weight, the core structure 35 is stronger than the core structure 10.

The relationship between the notches formed by offset portions 44a-b, 45ab, 49ab, and 50a-b with their associated cross wires 53a-g and 54a-g is substantially the same as previously described. Therefore, it will not be described again in connection with the core structure 35.

Referring now to FIGS. 7 and 8, there will be described a third preferred form which may be taken by wire core structure incorporating principles of the present invention. In FIG. 8, there is shown such third preferred form of wire core structure, indicated generally by the arrow 56. The core structure 56 is made up of wire core ribbons which are all the same, some of which extend in one direction, and the others of which extend at a right angle thereto. And, the core structure 56 does not include cross wires as in the previously described core structures 10 and 35.

The core structure 56 includes a set of parallel and equidistant first core ribbons 57a-b which are interspaced between a set of parallel and equidistant second core ribbons (of which only second core ribbon 57c is shown). And, as in the. case of the core structure 35, the second core ribbons, e.g., 57c, are ofiset longitudinally from the first core ribbons 57M a distance equal to one anchor section. Extending at a right angle to the core ribbons 57a-c there are provided a set of parallel and equidistant third core ribbons 57d, f, h, and j which are parallel to each other and spaced between a set of parallel and equidistant fourth core ribbons 57e, g, i, and k, which are also parallel to each other and equidistant apart. As can be seen, each of the core ribbons 57a-k lie in a separate plane which is perpendicular to the plane of the core structure 56.

Referring now to FIG. 7, the further details of the core ribbon 57a will be described in further detail. As in the prior core ribbons 15a-c, 40a-b, and 46a-b, the core ribbon 57a is formed of a wire which is bent at a series of right angles in order to provide a ribbon looking rather like a square wave with the anchor sections being equal to the joinder sections between the anchor sections. More particularly, the core ribbon 57a has a series of plane anchor sections 58a and notched anchor sections 59a, each of which lie generally in the plane of the core structure 56. The notched anchor sections 59a are offset inward toward the center of the ribbon, 60a, in order to provide a notch 61 at the mid-portion of the notched anchor section. These anchor sections 580 and 59a are joined together by joinder sections 62a extending at a right angle to the

anchor sections

58a and 59a as in the previously described core ribbons. It will be noted that the core ribbon 57a is different from the core ribbons l5ac, 40a-b, and 46a-b in that there is a notch provided only on the anchor sections on one side of the core ribbon, to wit, notched anchor sections 59a and not on the other side, to wit, plain anchor sections 58a. This is for a purpose which will be described.

Referring back to FIG. 8, it can be seen that the various portions of the various wire core ribbons 57a-k are all identical, and therefore, they have been given the same number with a different letter suffix for purposes of reference. More particularly, in FIG. 8, it can be seen that the core ribbons 57a-k have plain anchbr sections 58a-k and notched anchor sections 59a-k which anchor sections are joined by joinder sections 62a-k. Additionally, each of the notched anchor sections 59a-k is provided with an offset at 60ak for the purpose of providing the notch for the anchor section.

The purpose for providing a notch in the anchor sections on only one side will now be described. By way of example, it can be seen that the plain anchor section 580 extends through the particular notch provided by offset portion 60a in the notched anchor section If both the anchor section 580 and the anchor section 59e were notched, there would not be a proper matching of the parts.

The diameter of the plain anchor sections 59a-k are related to the notches provided in the notched anchor sections 59a-k in the same manner as the prior embodiments and the core ribbons 57ak are joined together by means of welding or adhesives such as described previously. Therefore, they will not be described herein again.

It can be seen that substantially the same machine which would make wire core ribbons ISa-c, 40a-b and/or 46a-b could be used to easily make the wire core ribbons 57a-k. This reduces the cost of manufacture of the core structure.

Referring now to FIGS. 9 to 11, there will be described a fourth preferred form which may be taken by core structure incorporating the principles of the present invention. In said F igs., there is shown such a third preferred core structure, indicated generally by the arrow 64. This core structure 64 has as its every other core ribbon a third preferred form which may be taken by core ribbons incorporating principles of the present invention. As can be seen in said FIGS. 9 to 11, said third preferred form of the core ribbon is a serpentine core ribbon. More particularly, there are provided serpentine core ribbons 65a-b; said ribbons having the same number with a separate letter suffix as they are the same. As best seen in FIG. 9, the serpentine core ribbon 65a has very short anchor sections at each apex of the serpentine form. More particularly, the serpentine ribbon 65a has joinder sections 66a extending diagonally between the apex portions where the sections are located. At each upper apex, there is located an offset portion 68 in order to provide a notch 69 for purposes which will be described. On either side of said notch 69, there is a protuberant portion 70a. At the lower apexes of the core ribbon 65a, there is provided offset portions 71a in order to provide a downwardly facing notch 72 having a protuberant portion 73 on either side thereof.

Between each pair of adjacent serpentine core ribbons, there is provided a core ribbon like the first preferred form a-c. In FIGS. 10 and 11, it can be seen that core ribbons 74a-c each include upper anchor sections 75a-c and lower anchor sections 76ac lying generally in the plane of the core structure 64. In fire upper anchor sections 75a-c, there are provided upper notches 77a-c for purposes to be described, which notches are the same as notch 21a. In the lower anchor sections 76ac there are provided ofiset portions at 78a-c for purposes of providing downwardly facing notches which are the same as notch 26a. For purposes of holding the serpentine core ribbons 65a and b in their desired parallel relationship with the core ribbons 74a-c, there are provided a plurality of upper cross wires 80a-d which are the direct parallel of the upper cross wires 23a-d. That is, the upper cross wires 80a-d extend through the notches in the upper apex of the serpentine core ribbons 65a-b and the notches 77a-c in the upper anchor sections 75a-c of the core ribbons 74a-c; said cross wires being joined to said core ribbons in any desired manner such as, for example, previously described.

correspondingly, the lower cross wires 81a-c are the direct counterpart of the cross wires 27a-d, and extend through the notches in the lower apexes of the serpentine core ribbons 65a-b (such as notch 72 in FIG. 9), and through the downwardly facing notches provided by the offset portions 78a-c; said cross wires being connected to said core ribbons in a manner such as described in connection with the cross wires 27a-d.

The relation of the cross wires 80a-d and 8la-c to the notches through which they extend is substantially the same as described in connection with the core structure 10 and need not be described further except as follows. In the case of the serpentine core ribbons 65a and b, the

protuberant portions

70a and 73 provide what is equivalent of the outside edge of the anchor sections in the core ribbons l5a-c.

Referring now to FIGS. 12 and 13, there will be described a fifth preferred form which may be taken by core structure incorporating principles of the present invention. In said FIGS. 12 and 13, there is shown a fifth preferred form of core structure which incorporates the principles of the present inven tion, which core structure is indicated generally by the arrow 82. As will be described, the core ribbons of this core structure 82 are very similar to the previously described core ribbons 15a-c with the exception that each anchor section is preferably twice as long as compared to the joinder sections of the core ribbon. Then, by using such core ribbons in pairs and offsetting one core ribbon of each pair relative to the other can be provided a resultant box beam core ribbon having a series of closed sections which are alternately spaced apart by upwardly open and downwardly open sections.

Referring to said FIGS. 12 and 13 in more detail, it can be seen that there are provided a set of first core ribbons 83a-e extending parallel to each other in equidistant relation. Each of thm core ribbons 83ae has a series of upper anchor sections 84a-e and lower anchor sections 85a-e which lie generally in the plane of the core structure. As in the prior embodiments, the anchor sections 84a-e and 85a-e are joined by vertical joinder sections (only joinder sections 86a can be seen in the drawings-in FIG. 13).

The core structure 82 also includes a set of second core ribbons 88a-e which are substantially the same as the first core ribbons 83a-e. More particularly, each of the second core ribbons 88a-e includes a series of upper anchor sections 89a-e and lower anchor sections 90a-e extending generally in the plane of the core structure 82. Said upper anchor sections 89a-e and lower anchor sections 90a-e are joined by joinder sections (however, only joinder sections 91a can be seen in the drawings-in FIG. 12).

As can be seen, each of the second core ribbons 88a-e are positioned along side and in contiguous relationship with a corresponding one of the first core ribbons 83a-e. Further, each of said second core ribbons 88a-e are offset from the associated one of the first core ribbons 83a-e a distance approximately equal to the thickness of the core structure 82 (i.e., the length of the joinder sections of the core ribbons). As best seen in FIG. 13 in relation to the

core ribbons

83a and 88a, there is provided a plurality of closed box sections 92 which are enclosed by a joinder section 86a and part of an upper anchor section 84a of the first core ribbon 83a and a joinder section 91a and part of a lower anchor section 900 of the second core ribbon 88a. Additionally, there is provided a series of closed box beams sections 93 which are enclosed by a joinder section 86a and part of a lower anchor section 85a of the first core ribbon 83a and a joinder section 91a and part of an anchor section 89a of the second core ribbon 880.

Further, there is provided a downwardly open section 94 between each pair of joinder sections 86a and 91a which downwardly open sections are closed at their upper sides by portions of said

upper anchor sections

84a and 89a. Further, there is provided a series of upwardly open sections 95 which are partially surrounded by said joinder sections 860 and 91a and are closed portions of lower anchor sections 85a and 90a.

As best seen in FIG. 12, the first core ribbons 83a-e are joined to the second core ribbons 88a-e along portions of their respective anchor sections. More particularly, the anchor sections 84a-e are joined to the anchor sections 89a-e along joinder lines 96a-e respectively. And, the lower anchor sections 85a-e and 90a-e are joined together along joinder lines 97a-e respectively. The joinder is accomplished by welding, or adhesive, means. With the core ribbons 83a-e and 88ae thus joined together there are provided resultant box beam core ribbons, indicated generally by the arrows 98a-e. These resultant box beam core ribbons 98a-e give extra strength.

In order to hold the resultant box beam core ribbons 98a-e in their desired parallel relations, they are placed so that the downwardly open sections 94 are in line. In this relation, a

pair

86 and 91 on either side of said downwardly open section.

Such connection can be accomplished simultaneously by having movable welding electrodes which can force the respective cross wires 89 outwardly against their respective joinder sec- 3. The core structure set forth in claim 1 wherein said first one of said cross wires is shaped like said core ribbons and has upper and lower anchor sections extending generally in plane of the core structure with a spacer section joining each ad- 5 jacent pair of upper and lower anchor sections, and each tions 86 and 91. Received in each of the upwardly open sections 95, there are a pair of cross wires 100. Said cross wires 100 are connected to the

joinder sections

86 and 91 on opposite sides of the upwardly open section in the same manner described in connection with the downwardly open section 94.

While only a few embodiments of the present invention have been shown and described in detail, it will be apparent to those skilled in the art that such is by way of illustration only, and numerous changes can be made thereto without departing from the spirit of the present invention.

1 claim:

1. A core structure of predetermined thickness adapted to be placed between two face sheets to form sandwich material, said core structure defining a horizontal plane and comprising:

a set of first core ribbons extending generally parallel to each other in a first direction, each of said first core ribbons having alternating upper and lower anchor sections extending generally parallel to said plane with a spacer section joining each adjacent upper and lower anchor section, each of said first core ribbons defining a vertical plane, at least some of said spacer sections on at least some of said ribbons extending at substantially a right angle to said plane of said core material, at least some of said anchor sections having on their outer sides which face away from the center of the core material a notch;

a set of cross wires extending parallel to each other in the plane of said core material and at a right angle to said first core ribbons, said cross wires being rigidly connected to said core ribbons so as to stabilize said core ribbons relative to each other, each of said notches at least partially receiving therein one of said cross wires;

and including a set of second core ribbons extending parallel to each other and to said first core ribbons, core ribbons of said second core ribbons being spaced alternately between adjacent ones of said first core ribbons, said second core ribbons having alternately upper and lower anchor sections joined by spacer sections, said anchor sections and spacer sections of said second core ribbons being substantially the same as said first core ribbons, said second ribbons being offset from said first ribbons such that a first one of said cross wires extending across the upper anchor sections of two adjacent ones of said first ribbons will be in line with a lower anchor section of a second core ribbon which is located between the last mentioned two first core ribbons.

2. The core structure set forth in claim 1 wherein:

said first one of said cross wires is in line with but spaced above said last mentioned lower anchor section.

upper anchor section of said last mentioned cross wire is connected to an upper anchor section of a core ribbon and each lower anchor section of said last mentioned cross wire is connected to a lower anchor section of a core ribbon.

4. A core structure of predetermined thickness adapted to be placed between two face sheets to form sandwich material, said core structure defining a horizontal plane and comprising:

a set of first core ribbons extending generally parallel to each other in a first direction, each of said first core ribbons having alternating upper and lower anchor sections extending generally parallel to said plane with a spacer section joining each adjacent upper and lower anchor section, each of said first core ribbons defining a vertical plane, at least some of said spacer sections on at least some of said ribbons extending at substantially a rrght angle to said plane of said core material;

a set of second core ribbons extending parallel to each other and to said first core ribbons, core ribbons of said second core ribbons being spaced alternately between adjacent ones of said first core ribbons, said second core ribbons having alternately upper and lower anchor sections joined by spacer sections, said anchor sections and spacer sections of said second core ribbons being substantially the same as said first core ribbons, said second core ribbons being offset from said first ribbons such that the upper anchor sections of two adjacent ones of said first ribbons will be in the same vertical plane with a lower anchor section of a second core ribbon which is located between said last mentioned two first core ribbons;

and a set of cross wires extending parallel to each other generally in the plane of said core material and being at a substantial angle to said first and second core ribbons, said cross wires being rigidly connected to said core ribbons at said anchor sections so as to stabilize said core ribbons relative to each other, at least some of said cross wires being shaped like said core ribbons and having upper and lower anchor sections extending generally in the plane of the core structure with a spacer section joining each adjacent pair of upper and lower anchor sections, and each upper anchor section of said last mentioned cross wires is connected to an upper anchor section of a core ribbon and each lower anchor section of said last mentioned cross wires is connected to a lower anchor section of a core ribbon,

5. The core structure set forth in claim 4 wherein at least some of said anchor sections are connected together by a weld of the material of which the core ribbons and cross wires are made.

Claims

2. The core structure set forth in claim 1 wherein: said first one of said cross wires is in line with but spaced above said last mentioned lower anchor section.
3. The core structure set forth in claim 1 wherein said first one of said cross wires is shaped like said core ribbons and has upper and lower anchor sections extending generally in plane of the core structure with a spacer section joining each adjacent pair of upper and lower anchor sections, and each upper anchor section of said last mentioned cross wire is connected to an upper anchor section of a core ribbon and each lower anchor section of said last mentioned cross wire is connected to a lower anchor section of a core ribbon.
4. A core structure of predetermined thickness adapted to be placed between two face sheets to form sandwich material, said core structure defining a horizontal plane and comprising: a set of first core ribbons extending generally parallel to each other in a first direction, each of said first core ribbons having alternating upper and lower anchor sections extending generally parallel to said plane with a spacer section joining each adjacent upper and lower anchor section, each of said first core ribbons defining a vertical plane, at least some of said spacer sections on at least some of said ribbons extending at substantially a right angle to said plane of said core material; a set of second core ribbons extending parallel to each other and to said first core ribbons, core ribbons of said second core ribbons being spaced alternately between adjacent ones of said first core ribbons, said second core ribbons having alternately upper and lower anchor sections joined by spacer sections, said anchor sections and spacer sections of said second core ribbons being substantially the same as said first core ribbons, said second core ribbons being offset from said first ribbons such that the upper anchor sections of two adjacent ones of said first ribbons will be in the same vertical plane with a lower anchor section of a second core ribbon which is located between said last mentioned two first core ribbons; and a set of cross wires extending parallel to each other generally in the plane of said core material and being at a substantial angle to said first and second core ribbons, said cross wires being rigidly connected to said core ribbons at said anchor sections so as to stabilize said core ribbons relative to each other, at least some of said cross wires being shaped like said core ribbons and having upper and lower anchor sections extending generally in the plane of the core structure with a spacer section joining each adjacent pair of upper and lower anchor sections, and each upper anchor section of said last mentioned cross wires is connected to an upper anchor section of a core ribbon and each lower anchor section of said last mentioned cross wires is connected to a lower anchor section of a core ribbon.
5. The core structure set forth in claim 4 wherein at least some of said anchor sections are connected together by a weld of the material of which the core ribbons and croSs wires are made.