US3058550A - Structural unit - Google Patents

Description

1962 D. RICHTER 3,058,550

STRUCTURAL UNIT Original Filed Aug. 5, 1957 8 Sheets-Sheet 1 IN V EN TOR.

Oct. 16, 1962 D. L. RICHTER 3,058,550

STRUCTURAL UNIT Original Filed Aug. 5, 1957 8 Sheets-Sheet 2 IN VEN TOR.

DazzaZd L. Ke'eidar D. L. RICHTER Oct. 16, 1962 WW f E IN VEN TOR. flozzaZd M BY M/VVMW Oct. 16, 1962 RlcHTER 3,058,550

STRUCTURAL UNIT Original Filed Aug. 5, 1957 8 Sheets-Sheet 4 INVENTOR.

Oct. 16, 1962 D. RICHTER 3,058,550

STRUCTURAL UNIT Original Filed Aug. 5, 1957 8 Sheets-Sheet 5 1 2' 5. Q INVENTOR. J fi zzald L. Bidder D. L. RICHTER STRUCTURAL UNIT Oct. 16, 1962 8 Sheets-Sheet 6 Original Filed Aug. 5, 1957 INVENTOR D. L. RICHTER STRUCTURAL UNIT Oct. 16, 1962 8 Sheets-Sheet '7 Original Filed Aug. 5, 1957 INVJNTO. DazzaZd 13. Racial? ATTO NEY Oct. 16, 1962 D. L. RICHTER 3,058,550

STRUCTURAL UNIT Original Filed Aug. 5, 1957 8 Sheets-Sheet 8 3,058,550 STRUCTURAL UNIT Donald L. Richter, Mount Prospect, 111., assignor to Kaiser Aluminum 8; Qhemical Corporation, Uaklaud, Calif a corporation of Delaware Original application Aug. 5, 1257, Ser. No. 676,223, new Patent No. 3,026,651, dated Mar. 28, 1962. Divided and this appiication Apr. 24, 1961, Ser. No. 168,702 36 Claims. (Cl. 189-1) This invention relates to building structures and the components therefor. More particularly, this invention relates to structural units of integrated form, wherein the individual units, when employed for fabrication of a roof, wall, spherical building or the like, comprise both the protective covering as well as the framework of the structure in which they are incorporated. This application also constitutes a division of application Serial No. 676,223, filed August 5, 1957, now Patent No. 3,026,651, which application Serial No. 676,223 is a continuationin-part of application Serial No. 632,893, filed January 7, 1957 and now abandoned.

One specific, though not the only, environment in which the structural units of the instant invention may be employed to great advantage is in the fabrication of geodesic domelike structures. Such domelike structures may be of the type shown and described in Fuller Patent 2,682,- 235. The structural unit of the instant invention also constitutes an improvement over any of the unit shapes and composite building elements disclosed in that patent.

Additionally, the structural unit herein described may find general utility in the fabrication of walls, roofs, etc., of more conventional design. When incorporated in these latter structures, the structural units provide a building structure having exceptional strength, lightness and attractiveness. The individual structural units themselves are unique in configuration. They are also rugged, light in weight and exceptionally easy to handle besides being easy to fabricate. Each of these units in a sense comprises a tetrahedral section or building block, which, when associated with and joined to similar building blocks, will form a unique covering for a building.

Accordingly, it is a primary object of this invention to provide a unique tetrahedral type structural unit, for use in building structures wherein the unit has an exceptionally high strength to weight ratio.

It is another object of this invention to provide a unique structural unit, for buildin structures wherein the framework of a finished architectural design is automatically formed by components of the structural units, as they are being emplaced.

It is a further object of this invention to provide a unique building structure made up of a plurality of structural units of the instant invention which are arranged in such a fashion that the distribution of stress approaches that of a uniform homogeneous shell under similar loading, and wherein the units may be advantageously arranged in such a fashion that they form a three-dimensional space-truss.

A further object of this invention is to provide a building structure comprised of a plurality of unique structural units, wherein each structural unit comprises both a stressed skin and part of the framework of the finished architectural design.

it is a further object of this invention to provide a unique structural unit, which, when assembled with other structural units of similar design will form a three-dimensional space-truss covering for a building with the various components of the structural units that form the framework of the building being arranged in turn along the arcs of great circles.

A further object of this invention is to provide a unique 3,6585% Patented Oct. 16, 1962 structural unit which because of its particular design and construction eifectively resists flexing and bending after installation of the same.

A further object of this invention is to provide a unique building structure made of structural units, which are roughly diamond-shaped in plan, with the units being so assembled together that the various load stresses imposed on the units are directed towards the several vertices or tips of the diamond-shaped units and wherein all the metal in each unit bears its full share of the load.

It is a further object of this invention to provide a spherical building made up of a plurality of unique diamond-shaped, tetrahedral units together with novel means for securing several units to each other, wherein the units comprise both the covering and structural framework for the building and wherein the means used to anchor the building to the ground and the portions of the units constituting the framework are arranged along the arcs of great circles.

A further object of this invention is to provide a building structure made up of a plurality of unique diamond-shaped tetrahedral units together with novel means for securing several units together adjacent the various vertices or tips of the units.

Another object of this invention is to provide a building structure made up of a plurality of unique diamondshaped tetrahedral units together with novel means for anchoring the structure formed from these units to the ground.

These and other objects of the instant invention not specifically referred to but inherent therein are accomplished by providing a building covering comprised of a plurality of three-dimensional tetrahedral-shaped panels. Each panel in turn is preferably comprised of a sheet of metal which is preferably diamond in shape. Portions of the diamond-shaped sheet metal are progressively bent or creased so that two opposing corners of the shape will be drawn upwardly from the normal plane of rest of the metal sheet. The displaced corners are connected by a bridging strut of any desired cross-sectional configuration. The edges of the sheet metal shape are also advantageously provided with marginal flanges, while the sheet metal itself may be embossed to provide it with suitable delineations impressed into the sheet during the shaping thereof, all of which will be more fully described hereinafter. These delineations not only enhance the overall appearance of the sheet metal, but they also prevent undesirable flexing in the sheet metal during use.

Other objects and advantages of the instant invention will become more apparent from a review of the following detailed description when taken in conjunction with the appended drawings wherein:

FIGURE 1 is a perspective View of the unique tetrahedral structural unit or panel of the instant invention, with reference planes being shown to emphasize the details thereof;

FIGURE 2 is a side-elevational view of the unit shown in FIGURE '1, the reference planes being omitted for the sake of clarity;

FIGURE 3 is an end-elevational view of the structural unit shown in FIGURES l and 2;

FIGURE 3a is an exploded perspective view of the structural unit of FIGURES 1-3 together with the basic components needed for securing the unit to similar units, during the construction of a wall, roof or other covering in a building structure;

FIGURE 4 is a plan view showing a representative geometric pattern, that may be formed by plurality of the structural units of the instant invention, when they are joined together;

FIGURE 5 is an example of one type of geodesic dome structure, such as that disclosed in Patent 2,682,235,

3) V which may be advantageously fabricated from the structural units of the instant invention;

FIGURE 5a is an example of another type of geodesic dome structure that may be fabricated by using the structural units of the instant invention and discloses one arrangement for anchoring certain of the units located along the perimeter of structure to ground piers in a unique fashion;

FIGURE 6 is a bottom plan View of a suitable type gusset member that may be used for joining a plurality of structural units together adjacent their long diagonals;

FIGURE 7 is a cross-sectional view of the gusset member shown in FIGURE 6 when taken along line 7-7 thereof;

FIGURE 8 is a further cross-sectional view of the gusset member shown in FIGURE 6, when taken along line 8-8 thereof;

FIGURE 9 is a fragmentary perspective view of the lower portion of the geodesic dome disclosed in FIGURE 5a and shows in more detail a unique arrangement for anchoring the dome to the ground by securing the anchoring elements to the proper reaction points on the dome or sphere;

FIGURE 10 is another bottom plan view of the gusset member shown in FIGURE 6 when anchored to several structural units adjacent their long diagonals; and with a structural supporting column shown in dotted lines also being secured to the gusset member;

FIGURE 11 is a plan view of the underside of a wall or three-dimensional space-truss formed by the structural units of the instant invention and discloses the manner in which three adjacent panels are joined together adjacent their short diagonals by means of a cluster of suitable gusset anchoring elements;

FIGURE 12 is an exploded view of the cluster of gusset anchoring elements shown in FIGURE 11;

FIGURE 13 is a broken front elevational view of a ground pier and a structural unit anchored thereto, and discloses the various accessories employed for securing the structural unit to the pier and to similar adjacent units;

FIGURE 14 is a sectional view taken along the line -14 of FIGURE 13;

FIGURE 15 is a sectional view taken along the line 15-15 of FIGURE 13 with parts removed for the sake of clarity;

FIGURE 16 is a bottom plan view of a modified cluster of gusset anchoring elements used to secure two structural units together when one of the units is anchored to a ground pier; and

FIGURE 17 is a side elevational view of a ground pier, with a structural unit and sphere supporting column anchored thereto.

With further reference to the drawings and in particular to FIGURES 1 and 3a it may be seen that the unique tetrahedral structural unit or building block of the instant invention is preferably comprised of a sheet metal element or panel 1, preferably diamond-shaped in plan view and having a major axis MM and minor axis NN. In most instances after forming, the major axis or the center long diagonal of the panel will also be slightly cambered upwardly from the true horizontal plane H. Major axis MM also lies in a true vertical plane V.

The minor axis NN is slightly above the horizontal plane H but is normal with respect to the axis MM and hence normal with respect to the vertical plane V. Although the minor axis NN is located slightly above horizontal plane H, it is normal with respect to the vertical plane V. The basic unit thus descr'ibed includes corners or vertices 2, 3, 4 and 5, corners 2 and 3 lying along major axis MM and corners 4 and 5 lying along the minor axis NN. Thus, it may be seen that since the corners 4 and 5 lie along the same line or minor axis NN and since the major axis MM lies along the intersection of planes H and V, the sheet metal forms a curve passing from corner 4 through the axis MM and thence to corner 5. The corners '4 and 5 are in turn connected to a suitably shaped strut member 6 which lies along and generally coincides with minor axis NN. This strut is also generally parallel to but vertically spaced from the plane H and normal to the plane V. The relation between the strut and sheet is more clearly discernable by inspection of shadow line S which would be cast on the sheet as shown in FIGURE 1. The strut is secured to the unit "1 at the corners 4 and 5 by means of an apertured flanged sleeve member, which fits over the end of the strut, or the ends of the strut may be provided with apertured flanged portions 6 disposed at the proper angle, with suitable bolts 7', rivets or the like passing through openings 8 in the flanges 6' and in corresponding openings 9', or holes in the panel unit -1 adjacent the corners 4 and 5.

Considering now the sheet or panel itself, attention will be given to the manner in which the arcuate configuration is imparted thereto. The basic sheet metal such as aluminum may simply be bent such that the corners 4 and 5 are displaced from their normal plane of rest. However, it is preferable that the sheet be provided with delineations in the manner and for the purpose to be described hereinafter. The sheet 1 is advantageously provided with a plurality of delineations or creases 12 and 13 which roughly form a unique quilted pattern. These delineations or creases are advantageously impressed in the sheet during the curving of the sheet; in fact, the edges or corners 4 and S are advantageously bent gradually upward to their predetermined position by creasing of the sheet 1 to form the delineations 12 and 13 in a conventional break press mechanism. This creasing is perfor-med by simply bending the sheet and without any deleterious stretching or weakening of the metal at the points of bending or creasing.

After the delineations have been impressed in the sheet, the marginal edges may be turned down to form the reinforcing marginal flanges 7 and 8, 9 and 11, whereby the creases 12 and 13 if impressed on the sheet prior to flanging will also be carried over into the flanges. If desired, the flanges may also be bent inwardly to form a flange tab 10. Delineations or creases 12 originate at the corner 2 and fan out in sunburst fashion therefrom and project toward the edges of the sheet as defined by the corners 5, 4 and 3. It will be noted that no single line 12 substantially coincides with the major axis MM, all delineations being disposed at an angle thereto. Similarly, delineations or creases 13 originate and fan out from the corner 3 to the sides defined between corners 5, 2 and 4 and again no delineations 13 coincide with the major axis MM but are angulated with respect thereto. Thus, the intersections of delineations 12 and 13 which take place intermediate the corners of the sheet and the delineations themselves form a unique reinforcing quilt-type pattern comprised roughly of a series of diamond-shaped figures and triangular figures of varying form and dimensions. The purpose of this delineated pattern is twofold. First, it will be appreciated that each of the resultant delineated geometrical figures may be angularly disposed one with respect to the other such that the sheet will be arched or curved in the manner indicated. Secondly, the pattern thus formed stabilizes the metal skin of the panel and precludes to a great extent the so-called oil canning, flexing or popping of the sheet during installations. In this connection, it is to be noted that the arrangement or pattern formed by delineations 12 and 13 is such that no continuous fold line is introduced into the sheet about which the sheet might tend to fold or collapse. These delineations serve an additional purpose in that they act as a network of reinforcing and load transmission elements, whereby the loads impressed on the structural unit are directed outwardly in a very eflicient manner towards the flanged portions and the vertices or tips thereof.

As indicated above, after the two sets of fan-shaped creases are imposed on the metal sheet during the arching thereof, the edges of the sheet are advantageously provided with downturned stiffening or reinforcing flanges 7, 8, 9 and 11, which extend from corners 2 to 4, 4 to 3, 3 to 5, and 5 to 2, respectively. These flanged edges of each of the structural units 1, as well as the struts and the long central diagonal of the metal sheet, advantageously act as the frame elements of the three-dimensional truss structure formed by an assemblage of the structural units of the instant invention in a manner to be more fully described hereinafter. Corners 2, 3, 4 and 5 may also be squared off for facility in assembling a plurality of units together.

While the fianging and pattern-forming operations have been described in terms of separate operations, it is quite possible and oftentimes most desirable that both the flanging and pattern-forming be conducted substantially as a single step resulting in the formation of a completed shape as shown in FIGURES 1, 2, 3 and 3a, with the exception of the strut 6.

The strut 6 which connects corners 4 and 5, as is clearly shown in FIGURES 1, 3 and 3a, can be rod-like and can be comprised of a tube, hollow bar or other structural shape, preferably having a high strength to weight ratio of which a tube is an excellent example. The strut may be welded, bolted, bracketed or otherwise secured to the arched, flanged, and delineated sheet. The strut may also be connected with the corners 4 and 5 in such a fashion that several stress conditions are imparted to the completed unit. For example, if the sheet is bowed or arched beyond its normal condition when delineated and flanged, the strut will be placed under a slight tensile stress, when it is fixed to the corners 4 and 5 since in order to fix the strut to the corners it will then be necessary to draw the corners 4 and 5 inwardly. If, however, the corners of the sheet must be drawn slightly outwardly from their initial bowed position as formed in order to secure the strut thereto, the strut 6 will then be placed under a slight compresion. If, however, the length of the strut and the distance between the corners 4 and 5 is substantially equal to the strut dimension, then no stress will be introduced to the strut. It will be appreciated, too, that while shown as a diamond with the strut being parallel to its minor axis, the sheet metal shape 1 may also be more on the order of a square with the strut 6 connected to either of the two opposite corners diagonally across the sheet. Alternately, the strut could be connected to the corners 2 and 3 of the diamond-shaped sheet so that it parallels the major axis of the diamond. This, of course, will depend upon the particular geometric pattern that is desired in the finished three-dimensional truss structure or other building unit formed from these units. In the latter case, where the strut is secured to the apices or corners 2 and 3 of the diamond-shaped sheet and parallel to the major axis thereof, it is obvious that corners 2 and 3 rather than 4 and 5 would be displaced upwardly from the plane of rest of the sheet and delineations 12 and 13 would likewise emanate from the corners 4 and 5.

There has thus been described a unique structural unit of unusual design and appearance. The sheet and the various components thereof are preferably formed of a light metal, such as aluminum. The unit described is light, strong and possesses an exceptionally pleasing appearance, when used in forming architectural shapes such as domes of the type mentioned previously, walls, roofs, ceilings and interior and exterior surfaces, and regardless of whether such structures are merely decorative or both decorative and functional.

It is to be noted that the single strut 6 between points 4 and 5 plus the formed diamond between points 2, 3, 4 and 5 in effect define a tetrahedron-like solid. The strut 6, the diamond edges 3-5, 52, 24 and 43, and the diamond valley between points 5M and M-4 define the 6 edges of the tetrahedronlike polyhedron formed by the sheet 1.

Considered another way, the tetrahedron-like solid may be considered as having one face formed by the diagonal on axis MM and diamond edges 35 and 5-4.; another face by the same diagonal and diamond edges 34 and 42; a further face by strut 6 and diamond edges 4-3 and 35; and the final face by strut 6 and diamond edges 5-2 and 2-4. In any event, the result is still a tetrahedral section.

When one section is joined to adjacent diamond sections to form a series of building blocks, each panel section in effect serves as a three-dimensional beam unit. The mathematical arrangement of this unit is such that load stresses are distributed substantially through all of the metal and are directed through the diamond vertices or tips. When all the diamond vertices of the various units are so arranged as to fall on the surface of a theoretical sphere, remarkable structural strength arises as a result. The overall effect is one of resolving all loads onto the substantially uniformly stressed spherical segments or structural units 1 in a fashion similar in principle to the high efficiency of an egg shell. As a result, each panel or structural unit 1 does not merely consist of a load-supporting framework covered with idle sheeting but in effect is a stressed skin self-reinforcing space-truss unit in which all metal bears its share of the load. Thus, it will be appreciated that such a tetrahedron-like element has considerable three-dimensional strength. The central portion of the sheet 1 located along line or plane MM, i.e., the long diagonal, also advantageously acts in the manner of a strut.

Having thus considered the individual units, several means of utilizing the units will now be described. One such use is the construction of domes, among them being geodesic domes of the type shown in US. Patent No. 2,682,235. The patent mentioned discloses a method of constructing domelike structures utilizing various geometric shapes along with a special assembled framework of struts bounding each shape, whether triangular, diamond or the like. The instant invention is an improvement particularly over the structure disclosed in the patent in that it requires the use of fewer and lighter parts, in addition to having general utility in other building structures.

Referring now to the manner in which the structural units herein disclosed may be utilized in forming a generally planar surface, it may be seen that a plurality of units, including flanged and bowed sheet metal shapes 1 and including a strut 6 are joined at a common point such as is seen in FIGURE 4. Six of the units have adjacent flanged edges in abutting relation. The struts 6 of each of the six units approximately define a regular hexagon. Located at the vertex point A from which the respective units radiate is a suitable hub element or rosette-like gusset 20, an example of which is shown in FIGURE 6. The corners 2 and 3 along the long diagonal of the units 1 are also advantageously connected to this gusset 2t.

In the case of the vertex point B at which the short diagonals of adjacent units converge, the short diagonal corners 4 or 5 of adjacent sheet metal panels may be joined together and in turn be reinforced by a cluster 24 of another type of hub element or hublike clamp element, an example of which is shown in FIGURES 3a and 11 and all of which will be described more fully hereinafter.

Each rosette 2i which may be an aluminum casting is comprised of a central hub or web portion 4% from which a plurality of spokelike members 42 radiate in the manner of a wheel. The center of the hub 40 may also be provided with an opening 43. Each spoke 42 is generally channel-shaped in cross-section and includes a web 44 and down-turned side flanges 45. A. combination sheet and strut 1 is anchored at one of its corners 2 or 3, to a rosette 20 by having the corner of the unit 1 and flanges 7-11 or 8-9 overlap the flanges 45 and a spoke 42 of the rosette 20 adjacent to the point where the spoke merges with the hub 40 as indicated particularly in FIGURE 10. When the gusset 20 is in place, a certain amount of open space will exist between the panel corners and the spokes of the gusset. These openings will be effectively closed 7 by the use of an outside cover plate 21, as indicated in dotted lines of FIGURE 10 and in full lines in FIGURE 9.

Plate 21 may be secured directly to the outside surfaces of the panels adjacent gusset 20 by means of an adhesive, or to the gusset 2i itself by means of a suitable bolt thrust through the opening 43. When bolts or rivets 23 are inserted in the openings 59 in the corners 2 or 3 of the unit 1 and similar openings 50' in the spokes 42 of the rosette 26), the converging corners of units will be securely locked to the rosette.

The structural units 1 are also advantageously secured to each other at their flanged portions 8 and 7, 9 and 11, by welding or by means of bolts or rivets 54 thrust through openings 52 in the flanges of the adjacent sheets. The struts 6 are also advantageously interconnected to each other in a unique fashion to be described more fully hereinafter such that there is effected a self-supporting framework in the form of a regular hexagon which, when the units are joined together, resists compressive stresses or the like in which the units would be inherently weak along their minor axes.

To the afore-described basic pattern, there may be added additional series of structural units so arranged that the struts 6 are connected to the six vertex points B of the basic hexagonlike frame and radiate outwardly from these points to the points R1, R2,, R3, R4, R and R6, all as is clearly shown in FIGURE 4. It may be seen that the edges of the sheets 3; of the integrated units now define a hexagon, the frame being comprised of a central regular hexagon surrounded by six half-shaped formed hexagons, each of which has one side common to the original geometric figure. Assuming now that the points R1 and R6 rest on suitable reaction points indicated as S1 and S2- in FIGURE 4, it may be seen that the straight edge at the bottom of the sheets may be continued by the addition of a half of unit 20'. This latter unit may advantageously have its strut 6 resting on reaction points S2. and S3. The strut 6 of this half unit 2%" may also be omitted, if desired.

The means for securing adjacent structural units at the corners 4 or 5 on the short diagonals thereof will now be described.

These means comprise a cluster 24 of hub clamps 61, 62 and 63. These may be made in the form of castings, and each clamp is securable to a separate unit 1 adjacent the corner 4 or 5 on the short diagonal thereof. Ordinarily, the short diagonal corners of three units 1 will converge at the vertex point B because of the geometric pattern fo-nned by the units 1. Thus, only three hub clamps will be used. Hub clamp 61 includes an inclined outer bearing surface 64 for engaging the bottom surface of a structural unit 1 adjacent a corner 4 or 5 thereof and a partially arcuate boss 65 which contacts the rounded off portion 66 of the hub clamp 62. Boss 65 is provided with a central aperture 68 and bearing surface 64 with a plurality of openings 69. Openings 69 register with corresponding openings 9 in a structural unit 1 so that bolts or rivets 77 may be inserted therein to lock the clamp to the structural unit. Hub clamp 62 in addition to having rounded off portion 6-6 also includes an inclined outer bearing surface 69' for contacting the corner 4 or 5 of a structural unit 1. Bearing surface 69' has openings 79 therein and rounded otf portion 66 has a central opening 71. Openings 7% as in the case of clamp 61 register with similar openings 9' in a structural unit 1. Clamp 63 is also provided with an inclined outer bearing surface 73 for contacting the inside surface of a structural unit 1 and a downwardly projecting rounded boss 74. Bearing surface 73 has openings 75 therein, while boss 74 has a central opening 76 therein. The openings 75 register with corresponding openings 9 in a structural unit so that rivets or bolts 77 may be inserted therein to lock the clamp to a structural unit. Each of the hub clamps may also be provided with several sets of reinforcing ribs. After the inclined bearing surfaces 64, 69' and 73 of the several clamps are secured to the several structural units 1, they are then secured together by means of a bolt 78 thrust through the openings 68, 71 and 76 in the several hub clamps and a nut 79, all as clearly indicated in FIGURE 11. The rounded off portions 66 of clamp 62, as well as the rounded off bosses 65 and 74 of clamps 61 and 63, also permit ready adjustment of the clamps one with respect to the other during the period they are locked together. The inclination of the bearing surfaces 64, 69 and '73 also coincides substantially with the slope of the units 1 adjacent corners 4 and 5. The open spaces that may be present at the point where the cluster 24 of hub clamps secure the short diagonals of adjacent units together may be substantially eliminated, if desired, by means of a cover plate 82 applied over the outer surfaces of the several units, the cover plate 82 being held in place by a suitable adhesive securing it directly to the top surface of the sheets, or alternatively by thebolt 78. Such a cover plate is shown in dotted lines in FIGURE .1.

It is also of interest to note in connection with the vertices B or points where the corners of the short diagonals of the structural units 1 converge that they form the apices of a plurality of pyramidal type units when the long diagonal of each unit is considered as a frame member in the over-all framework of the sphere or dome and with the long diagonal of each unit 1 serving as a base line for a pyramid. The strut 6 serves to connect the apices of each pyramidal type unit.

Finally, the manner of connecting the various panels together, along with their struts at the short diagonls thereof, is such that the struts on adjacent units are also interconnected with each other whereby the struts advantageously transfer loads from one to the other. The outside appearance of the building is also enhanced in that gussets 20 and hub clamp clusters 24 are located inside of the building and are concealed from the view of one looking at the building from the outside.

By use of the structural panels 1 herein described, a unique structure is formed having a geometrically-patterned spiderlike framework comprised of struts 6 and a surface wall of undulating, marginally-joined diamondshaped sheets. The geometric pattern of the frame is generally a series of reoccurring hexagons. Each diamond with its respective strut defines a tetrahedron-like threedimensional structure and as shown in FIGURES 4, 5 and 5a, these tetrahedron-like elements are joined edge to edge in such a manner that the space between every three joined to the common point is also a tetrahedron. Thus, the total assembly may be considered a three-dimensional space-truss of considerable strength. The combination and interaction of struts and diamonds will provide an exceptionally strong structural surface such as a flat single or double curved wall or roof. It will also be noted that by appropriate portioning 0f the diamond and strut dimensions the pattern defined by the struts in FIG- URE 4 can be other than hexagons, that is, any number more than three diamonds can be associated about the one common vertex.

A similar construction may be used in forming roof structures. In such a case, it is preferable that the overall surface be somewhat arched such that the primary support for the roof as such comprises the framework made up of the geometric arrangement of struts 6 plus the skin elements themselves and with the center line and the flanged edges of each structural element in effect also acting as struts in the manner previously described. Thus, the sole support for a roof area of large size such as over an auditorium, theatre, threatre shop or the like would be furnished by the above described framework in combination with a suitable sidewall structure leaving the enclosed area unobstructed by posts, columns or the like. In the event the interruption of the closed area is not a prime consideration, the roof structure may be substantially level, the geometric frame being supported at selected points throughout its expanse and with suitable drain means being provided to collect moisture from the troughs defined by the bowed or arched sheets 1. Re-

.in only one inclined plane to the vertical.

ferring now to geodesic dome-shaped structures such as are shown in FIGURES and So, it may be seen that the individual units may be utilized in such a manner as to fabricate a dome structure of the type referred to in the above-mentioned Fuller patent with reaction points S S7 being shown for the structure of FIGURE 5 and reaction points S S being shown for the structure of FIGURE 5a.

It is to be understood that suitable sealants may be applied between the flanged edges of abutting units and at the vertex points A and B where the corners 2 or 3, and 4 or 5, respectively, of the several panel units converge. One suitable type sealing compound which has been found satisfactory for this purpose is one known as Thiokol, a synthetic rubber-based sealing compound manufactured and sold by Minnesota Mining and Mannfacturing Company.

The preferred way of utilizing the structural units 1 to the greatest advantage, such that equal or near equal stress distribution is obtained throughout the entire framework, is as has been described, that is, by forming an appropriate series of approximately regular hexagons. A dome or sphere made up of such units and patterns is clearly shown in FIGURES 5 and 5a, wherein each strut 6, the long and short diagonals and the marginal flanges 7, 11, 8 and 9 of any two contiguous units are positioned along great circle arcs utilizing in full the geometry as taught in the Fuller patent.

On occasion the metal units 1 may be replaced by those made of plastic, glass or other transparent materials for lighting and decorative effects. Windows, entrances and exits may also be incorporated in the dome structure.

In one form of the invention and as indicated particularly in FIGURES 5a and 9, in those instances where it is desirable to leave some open area adjacent the bottom perimeter of the sphere, unique means are provided for supporting and anchoring the sphere to the ground. These means are shown particularly in FIGURES 5a and 9, and 13-17. In this instance, the bottom extremities of a plurality of panel units 1 are directly anchored to the ground piers 80. Main support columns 81 are also connected to the piers 3t) and to the sphere at the vertex points A.

As indicated particularly in FIGURES 5a and 9 the anchoring piers 8t and support columns 81 are arranged in perimetric groups to conform with the curvature of the sphere and geometric arrangement of the panel units 1. In each of these groups the centermost diamond-shaped sheet and its associated column 81 are generally located The downwardly projecting diamond-shaped sheets and their associated columns 81 on either side of the centermost downwardly projecting diamond-shaped sheet and its associated column 81, since they are radially disposed with respect to these centermost sheets and columns, are inclined in two planes.

As indicated particularly in FIGURE 13, each panel unit 1 is anchored at a long diagonal corner to a pier 80 by means of a somewhat Y-shaped plate 82. The stem 83 of the plate 82 is inserted between the upstanding plates 85 of the anchoring assembly 86 and loosely held therein. It is not positively anchored between the plates, and this permits freedom of movement such as may be caused by expansion and contraction of the dome assembly as a whole. Plates 85 in turn are welded or otherwise secured to a shoe plate 87 welded to a base plate 87'. Base plate 87' is anchored by suitable stud bolts 35 to the concrete pier 8%. The ends of plates 85 are welded to the end covers 88, and covers 88 are welded to plates 87 and 87. In the case of the panel units 1 which are tilted or inclined in two planes, the plates 85 will also be somewhat tilted with respect to a true vertical in order to accommodate the panel unit and support column 81. The upper winged portions 9t and 9t) of plate 8'2 are inserted within the channels formed by the flanges 7 and 11 and flange tabs thereon. Suitable elongated L- 10 shaped shim members 91 and 91 are also sandwiched in between the winged portions 90 and 90' of plate 82 and flanges i and 11 of the panel unit 1. The wing portions 9'0 and 91) of plate 82 are bolted directly to the base flanges 93 and 93 of these shim members 91 and 91, while the upstanding flanges 94 and 94 of the shim members are bolted or riveted to the flanges 11 and 7, respectively, of the panel unit 1. If desired, a fitting 95 shown in dotted lines in FIGURE 13 may be inserted in the opening between the shim members 91 and 91 and flanges '7 and 11 and tabs 1% to further rigidity the shim members with respect to the flanged edges of the sheet metal unit 1, such a space 96 being shown in FIGURE 15. This fitting 9'5 would be secured by suitable means not shown both to shim member 91 or 91 and the flange tabs 11!.

Pivotally mounted between and secured to the several plates 85, outwardly from the panel unit 1, is the lower extremity of a main support column 81. As indicated in FIGURE 17, this lower extremity of the column comprises a flat plate 98 inserted in a suitable slot in the column and then welded thereto. This flat plate is pivotally secured to plates 85 by bolt means 99. Secured to the upper extremity of column 81 in a fashion similar to plate 98 is another plate 100 indicated in dotted lines in FIGURE 10. It will be noted, however, that plate 1% is disposed at approximately a 90 angle to plate 98. The top of plate 100 and in turn the column is directly anchored to a gusset 20 in one of the lowermost vertex points A on the sphere. As indicated particularly in FIGURES 5a and 9, these latter vertex points A serve as the main reaction points for all loads and tension and compressive forces transmitted through the building framework, which includes, of course, the center long diagonal of each panel unit, all as indicated in dotted lines in FIGURES 5a and 9. These loads in turn are then transmitted into and through the columns 81 to the piers 80. It will also be observed by reference to FIG- URE 9 that each column fits underneath the strut 6 of the panel unit 1, with which it is associated. By loosely anchoring the base supporting panel units 1 and pivotally anchoring columns 81 to the piers 8t any expansion or contraction in the sphere is readily compensated for. The panels are also advantageously contained by piers 80 in order to stabilize the sphere against translating, twisting and rotating.

With further reference to the drawings and in particular FIGURES 9, 13 and 16 in the case of where the corners 4 and 5 on the short diagonals of two adjacent panels meet and are joined together, and where the corner 4 of one panel unit 1 secured to a pier $0 is also secured to an adjacent unit, only two clamp elements are employed, such as clamp elements 62 and 63. Considering FIGURE 16 as a view of the joint between corner 5 on the panel unit 1 secured to a pier and the corner 4 of the adjacent panel unit and looking from the inside out, the clamp element 62 is secured to corner 1 of one panel unit and the clamp element 63 to corner 5 of the other panel unit. In an effort to further strengthen the joint between the two panel units, it is also contemplated that a roughly Z-shaped reinforcing finger element 12 may be used. Each finger element, as indicated particularly in FIG- URES 13, 15 and 16, includes a bottom extremity 1tl3 bolted to the base flange 93 of the shim member 91, a Web 104- and an upper rounded and apertured extremity 1415 bolted directly to the clamp elements 62 and 63 by means of the bolt 78 and nut 79.

From the above description it will be noted that when a plurality of these tetrahedral blocks are assembled as described, such as in a spherical building, the total arrangement becomes that of a hexagonal strut overlying a three-dimensional covering of diamond-shaped panels. The whole is structurally interacting to form a highly e-f ficient member which geometrically defines a shell segment of a sphere. The resultant structure is also a true ll space-truss being triangulated three dimensionally, and defining tetrahedrons. It is also geodesic in that the vertices of all tetrahedral building blocks or structural elements fall in a series of great circles, which define a sphere in the case of the building structures shown in FIGURES 5, a and 9.

The various panels and all accessories therefor used in making the spherical building described are preferably made of aluminum although it is understood that other materials may also be employed as desired. One advantage of the structural unit herein described is the fact that the units can be made of larger or smaller size, depending upon the type of structure in which they are to be incorporated. In any event, utilizing the units of the instant invention, the area to be covered is calculated along with the best possible size for the individual structural units. Then by considering the edges as terminating in a series of half and whole hexagons or other polygons, the number of units may be easily calculated with a slight compensation in turn being made for each unit such that once the appropriate geometric pattern is established, the remainder of the pattern is also established.

in all cases wherein the preferred form of the invention is used, an exceptionally strong, easily fabricated, lightweight attractive structure is provided. It will be appreciated that various changes can be made in the described invention which are within the scope thereof, the invention being limited only as defined in the following claims.

What is claimed is:

1. A stressed skin tetrahedron-like three-dimensional structural unit comprised of a four-cornered sheet metal shape, said sheet metal shape being bowed about an axis lying substantially in a plane dividing said shape from one corner to the diametrically opposite corner, the diagonal portion of the shape lying between said one corner and said diametrically opposite corner constituting a loadsupporting and stabilizing frame member, said unit further including a rod-like strut connected to the other two opposing corners of said shape and bridging the space between said last-mentioned corners, said strut also being normal to said plane in which said axis lies.

2. A structural unit as defined in claim 1 wherein said sheet metal shape and said strut are comprised of a light metal.

3. A structural unit as defined in claim 1 wherein said sheet metal shape has a diamond configuration in plan, said strut paralleling the shorter of the two corner-tocorner dimensions.

4. A tetrahedron-like three-dimensional structural unit comprising a four-cornered sheet metal shape, said shape being bowed about an axis lying substantially in a plane dividing said shape diagonally from one corner to the diametrically opposite corner, the diagonal portion of the shape lying between said one corner and said diametrically opposite corner constituting a load-supporting and stabilizing frame member, a rod-like strut disposed diagonally of said shape and connected to the other diametrically opposite corners thereof, the strut being normal to the plane in which said axis lies, said sheet metal shape also being creased to prevent oil canning thereof.

5. A structural unit as defined in claim 4 wherein said sheet metal shape and said strut are comprised of aluminum.

6. A tetrahedron-like three-dimensional structural unit comprising a four-cornered sheet metal shape, said shape being progressively bowed about an axis lying substantially in a plane, bisecting said shape diagonally from one corner to another corner, and the bowed portion of the shape 'being further defined by a series of creases emanating from each of the said corners of the shape and a rodlike strut disposed diagonally of said shape and connected to a pair of diametrically opposed corners.

7. 'A tetrahedron-like three-dimensional structural unit comprising a diamond-shaped sheet being deformed from 12. V its normal plane of rest such that two corners thereof are raised from said plane of rest, a strut member connecting said corners, the portion of the sheet between said raised corners defining an are, a series of creases in said sheet, said creases emanating as a series of intersecting radii from the corners lying in the normal plane of rest of said sheet and the edges of said sheet being flanged and defining straight corner-to-corner peripheral edges.

8. A structural unit as defined in claim 7 wherein said creases are carried over into said flanges.

9. A structural unit as defined in claim 7 wherein said sheet and said strut are comprised of a light metal.

10. A building structure comprised of a plurality of stressed skin tetrahedron-like structural units, each of said units comprising a four-cornered, generally diamondshaped sheet, said sheet being bowed such that the two corners thereof are displaced upwardly from the normal plane of rest of said sheet, the diagonal portion of the sheet lying between the other two corners of the sheet constituting a load-supporting and stabilizing frame member, a strut extending across said sheet and connected solely at its ends to said upwardly displaced corners, the edges of said sheet being flanged, said units being connected in a regular geometric pattern such that a series of regular polygons are formed by said struts, means including hub elements connecting said units and struts together whereby said struts form a self-supporting interconnected framework and loads are transferred from one strut to another strut.

11. The building structure as defined in claim 10 wherein the series of regular polygons formed by said struts are hexagons.

12. In a building structure a plurality of structural units, each of said units comprising a four-cornered, generally diamond-shaped sheet, said sheet being bowed such that two corners thereof are displaced upwardly from the normal plane of rest of said sheet, a series of creases in said sheet, said creases emanating as a series of intersecting radii from the corners lying in the normal plan of rest of said sheet, a strut extending across said sheet and connected at its ends to said upwardly displaced corners, flanges on the marginal edges of said sheet, said creases also being carried over into the said flanges, and means anchoring said structural units in a fixed pattern, said means including a rosette-type element provided with a series of radiating spoke-like elements, each of which is secured to one extremity of a different structural unit, whereby, when said structural units are connected to said rosette-type element and to each other, they form a geometric pattern such that a regular polygon is formed by the struts on the said units.

13. The building structure as defined in claim 10 wherein the regular polygon formed by the struts is a hexagon.

14. As an article of manufacture for use as a building panel, a four-cornered sheet metal shape, said shape constituting a combined frame and covering and said shape being progressively bowed about an axis which lies substantially in a plane bisecting said shape diagonally from one corner to the diametrically opposite corner thereof, the diagonal portion of the shape lying between said one corner and said diametrically opposite corner constituting a load-supporting and stabilizing frame member, the bowed portions of the shape being further defined by a first series of creases which emanate radially from one of said corners, and a second series of creases, which emanate radially from the other of said corners and intersect with said first-mentioned series of creases at an intermediate portion of said sheet metal shape, thereby minimizing flexing of the shape when loads are imposed thereon during use.

15. An article of manufacture for use as a building panel as defined in claim 14, wherein the marginal edges of said shape intermediate the corners thereof are flanged.

16. An article of manufacture for use as a building panel comprising a generally diamond-shaped sheet metal shape, said shape constituting a combined frame and covering and said sheet metal shape being progressively bowed upwardly about the longer axis of said shape and bisecting said shape diagonally from one corner to the diametrically opposite corner thereof, the longer axial portion of the shape constituting a load-supporting and stabilizing frame member, the bowed portions of the shape being further defined by a first series of creases which emanate radially from one of the said corners and a second series of creases which emanate from the other of said corners, both of said series of creases intersecting with each other at an intermediate portion of the sheet metal shape whereby the flexing of the shape during use and when subjected to loads is minimized.

17. An article of manufacture as defined in claim 16, wherein the marginal edges of said shape intermediate the corners thereof are flanged.

18. In a building structure a plurality of contiguous stressed skin tetrahedron-like structural units so disposed with respect to each other as to form a three-dimensional space-truss, each of said units comprising a four-cornered sheet metal panel, said sheet metal panel being bowed about an axis dividing said panel diagonally such that two opposing corners thereof are displaced upwardly from the normal plane of rest of the panel, the diagonal portion of the panel lying between the other two opposing corners of the panel constituting a load-supporting and stabilizing frame member, a strut extending across said panel and connected at its ends to said upwardly displaced corners, means formed integrally with a panel and reinforcing the margins of each panel intermediate the corners thereof, means including hub elements anchoring contiguous panels to each other to form a fixed geometric pattern, said hub elements also interconnecting the struts on adjacent units with each other whereby said struts form a self-supporting framework and loads can be transferred from one strut to another strut, the contiguous reinforced margins of any two contiguous panels combining to form a structural frame element aligned with the strut of another structural unit of said three-dimensional spacetruss.

19. A building structure as defined in claim 18 wherein each of said panels is diamond-shaped and the said panel is bowed about the longer axis thereof.

20. A building structure as defined in-claim 18 wherein the said struts and reinforced margins of each panel are located along great circle arcs with the strut of any one panel combining with the reinforced margins of the same and two contiguous panels to form a three-way grid.

21. In a building structure of generally spherical form, a plurality of stressed skin tetrahedron-like structural units so constructed and disposed with respect to each other as to form a three-dimensional space-truss, each of said units comprising a four-cornered sheet metal panel, said panel in turn being bowed about an axis coinciding with a diagonal center line in the said panel such that two opposing corners thereof are displaced upwardly from the normal plane of rest of the panel, a strut extending across said panel and connected at its ends with said upwardly displaced corners, means formed integrally with a panel and reinforcing the margins of each of said panels intermedi ate the corners thereof, means including hub elements anchoring contiguous panels together in a fixed geometrical pattern, said hub elements also interconnecting the struts on adjacent panels with each other, whereby said struts form a self-supporting framework and loads can be transferred from one strut to another strut, the contiguous reinforced margins of any two contiguous panels combining to form a structural frame element aligned with the strut of another unit in the said three-dimensional truss, the diagonal center line of each panel which constitutes the axis about which the panel is bowed also serving as a structural frame element in the said truss.

22. The building structure as defined in claim 21,

14 wherein each of the said structural units is diamondshaped in plan.

23. The building structure as defined in claim 21, wherein the struts, the diagonal center line and the reinforced margins of each panel are all located along great circle arcs, with the strut of any panel combining with the reinforced margins of the same and two contiguous panels to form a three-way grid.

24. In a building structure, a plurality of contiguous structural panels, so constructed and so disposed with respect to each other as to form a three-dimensional spacetruss and a fixed geometrical pattern, each of said panels comprising a diamond-shaped sheet, said sheet being bowed about an axis coinciding with the long diagonal of the sheet such that the two corners of the sheet on the short diagonal thereof are displaced upwardly from the normal plane of rest of the sheet, a strut member extending across the panel and connected at its ends to said displaced corners, means anchoring contiguous panels together, said means including hub elements, portions of which are secured to the individual corners of each panel at the vertices on said three-dimensional space-truss that are formed at the points on the truss where the corners of the said panels converge, and the long diagonal of each sheet which constitutes the axis about which the sheet is bowed also serving as a structural frame element in the said truss, the strut members on the panels also being connected to certain of said hub elements and said strut members forming an interconnected self-supporting framework, whereby loads can be transferred from one strut member to another strut member.

25. The combination set forth in claim 24, wherein certain of the hub elements comprise a gusset member having radially disposed spokes, the individual spokes of which are secured to the corner of a diamond-shaped sheet, which is located on the long diagonal thereof.

26. In a building structure, a plurality of contiguous structural panels, so constructed and so disposed with respect to each other as to form a three-dimensional spacetruss and a fixed geometrical pattern, each of said panels comprising a diamond-shaped sheet, said sheet being bowed about an axis coinciding with the long diagonal of the sheet such that the two corners of the sheet on the short diagonal thereof are displaced upwardly from the normal plane of rest of the sheet, a strut member extending across the panel and connected at its ends to said displaced corners, means anchoring contiguous panels together, said means including hub elements, portions of which are secured to the individual corners of each panel at the vertices on said three-dimensional space-truss that are formed at the points on the truss where the corners of the said panels converge, and the long diagonal of each sheet which constitutes the axis about which the sheet is bowed also serving as a structural frame element in the said truss and certain of said hub elements comprising clusters of separate hub clamps, portions of each hub clamp being secured to the other hub clamps in the said cluster and other portions of each hub clamp being interconnected with the corner of a sheet which is located on the short diagonal thereof.

27. The combination as set forth in claim 26, wherein the strut members on the units are also connected at their extremities to the hub clamps in said clusters of hub clamps.

28. In a building structure, a plurality of contiguous structural units so constructed and disposed with respect to each other as to form a three-dimensional space-truss, each of said units comprising a diamond-shaped panel, said panel being bowed about an axis coinciding with the long diagonal of the diamond such that two corners of the panel on the short diagonal thereof are displaced upwardly from the normal plane of rest of the panel, a stint member extending across the panel and connected at its ends to said displaced corners, means anchoring a group of panels together at the vertices on the three-dimensional space-truss, that are formed by the converging corners of the structural units which are located on the long diagonals thereof, said means including spoke-like elements, the individual spokes of which are secured to separate long diagonal corners of individual structural units, and means anchoring a group of panels together at the vertices on the three-dimensional space-truss, which are formed by the converging corners of the structural units, which are located on the short diagonals thereof, said means comprising a cluster of separate hub clamps for each of the last mentioned vertices, one portion of each hub clamp being secured to the other hub clamps in the said cluster and another portion of each hub clamp being secured to a last-mentioned corner of a structural unit.

29. In a building of generally spherical form, a plurality of structural units so disposed and secured to each other as to form a three-dimensional space-truss, each of said units comprising a four-cornered sheet metal panel, said panel in turn being bowed about an axis coinciding with a diagonal center line in the said panel, such that two opposing corners thereof are displaced upwardly from the normal plane of rest of the panel, a strut member extending across and connected at its ends to said upwardly V displaced corners, means securing contiguous panels together, said means including a first hub means securing together the converging corners of a plurality of panels which corners are located along the said diagonal center line thereof, a second hub means securing other converging corners of a plurality of panels together, said last mentioned corners being located along the other diagonal lines of the said panels, said second hub means comprising a plurality of clamp-like elements individually adjustable with respect to each other, said clamp-like elements being connected to each other and to the last mentioned corners on different panels.

30. The building structure as defined in claim 29 wherein the ends of the strut members on the said panels are also connected to said clamp-like elements.

31. The combination as set forth in claim 29 wherein each of said clamp-like elements comprises a panel corner engaging portion and an apertured end portion, and common means for securing said clamp-like elements together at the said end portions thereof.

32. The building as defined in claim 29 wherein the structural units are comprised of diamond-shaped panels, said first-mentioned hub means securing those panel corners together, which are located on the long diagonal of the diamond-shaped panels and with said second-mentioned hub means securing the panel corners together, which are located on the short diagonal of the diamondshaped panels.

33. As an article of manufacture a stressed skin tetrahedron-like three-dimensional structural unit adaptable for use in a building structure, with certain integral portions of the unit serving as the covering and other integral portions of the unit serving as the framework of the said building structure, said unit comprising a four-cornered sheet, said sheet being bowedsabout an axis lying substantially in a plane dividing said sheet from one corner to the diametrically opposite corner, the diagonal portion of the sheet lying between said one corner and said diametrically opposite corner constituting a load-supporting and stabilizing frame member, said unit further including a rod-like strut connected to the other two opposing corners of said sheet and bridging the space between said 16 last-mentioned corners, said strut'also being normal to said plane in which said axis lies.

34. A building structure comprised of a plurality of stressed skin tetrahedron-like structural units, certain integral portions of the units serving as the covering for the building structure and other integral portions of the units serving as a framework for the building structure, each of said units comprising a four-cornered sheet, said sheet being bowed such that two oppositely disposed corners thereof are displaced upwardly from the normal plane of rest of said sheet, a strut extending across said sheet and connected at its ends tosaid upwardly displaced corners, said units being connected in a regular geometric pattern such that a series of regular polygons are formed by said struts and said struts forming a self-supporting framework, the portion of such sheet which constitutes the axis about which the sheet is bowed also constituting a structural frame element of the framework, means including hub elements connecting said struts together whereby said struts can form said self-supporting framework and loads can be transferred from one strut to another strut.

35. A tetrahedron-like three-dimensional structural unit comprising a four-cornered sheet metal shape, said shape being bowed about an axis lying substantially in a plane dividing said shape diagonally from one corner to the diametrically opposite corner, the diagonal portion of the shape lying between said one corner and said diametrically opposite corner constituting a load-supporting and stabilizing frame member, a strut disposed diagonally of said shape and connected to the other diametrically opposite corners thereof, the strut being normal to the plane in which said axis lies, said sheet metal shape also being creased to prevent oil canning thereof-and with the creases comprising a series of intersecting radii emanating from the corners through which the plane containing the said axis lies.

36. In a building structure, a plurality of tetrahedronlike three-dimensional structural units, each of said units comprising a four-cornered, generally diamond-shaped sheet, said sheet being bowed such that two corners thereof are displaced upwardly from the normal plane of rest of said sheet, the diagonal portion of the sheet lying between the other two corners thereof constituting a loadsupporting and stabilizing frame member, a strut extending across said sheet and connected at its ends to said upwardly displaced corners, flanges on the marginal edges of said sheet and means anchoring said structural units in a fixed pattern, said means including a wheel-like member provided with spoke elements, each of which is secured to one extremity of a structural unit, whereby when said structural units are connected with said wheel-like member and to each other they form a geometric pattern such that a regular polygon is formed by the struts on said units and each of said sheets being provided with a series of creases which emanate as a series of intersecting radii from certain opposing corners of said sheet.

References Cited in the file of this patent UNITED STATES PATENTS 2,383,370 Dean Aug. 21, 1945 2,484,096 Kay Oct. 11, 1949 2,682,235 Fuller June 29, 1954 2,725,126 Ely Nov. 29, 1955 2,918,992 Gelsavage Dec. 29, 1959

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