US3045313A

US3045313A - Scaffold for supporting formwork, particularly sliding or climbing molds

Info

Publication number: US3045313A
Application number: US842163A
Authority: US
Inventors: Dorn Hans
Original assignee: Acrow Wolff Fa GmbH
Current assignee: Acrow Wolff Fa GmbH; ACROW-WOLFF Firma GmbH
Priority date: 1958-09-30
Filing date: 1959-09-24
Publication date: 1962-07-24
Anticipated expiration: 1979-07-24

Description

July 24, 1962 DORN 3 045,313

H SCAFFOLD FOR SUPPORTING FORMWORK, PARTICULARLY SLIDING OR CLIMBING MOLDS Filed Sept. 24, 1959 4 Sheets-Sheet 2 July 24, 1962 H. DORN 3,045,313

SCAFFOLD FOR SUPPORTING FORMWORK, PARTICULARLY SLIDING OR CLIMBING MOLDS 4 Sheets-Sheet 3 Filed Sept. 24, 1959 4, F a 6 W i TW #7 7 Anhuw AMV \w W m T m I- .9 m m m r n a l I 3 a b ,1 n n E I 8 o d, W ll 7 W /m U um m 9 W 1 9 F a n o 1 W Inventor? H. DORN July 24, 1962 SCAFF'OLD FOR SUPPORTING ,FORMWORK, PARTICULARLY SLIDING OR CLIMBING MOLDS 4 Sheets-Sheet 4 Filed Sept. 24, 1959 jm/eman' I l 1 i l 1 United States Patent 3,045,313 SCAFFOLD FOR SUPPORTING FORMWORK, PAR- TICULARLY SLIDING R CLlll/IBING MOLDS Hans Dom, Dusseldorf, Germany, assignor to Firma Acrow-Wollf Gesellschaft mit beschrankter Haftung, Dusseldorf, Germany Filed Sept. 24, 1959, Ser. No. 842,163 Claims priority, application Germany Sept. 30, 1958 Claims. (Cl. 25-131) The present invention relates to a scaffold for supporting formwork, particularly sliding'or climbing molds for concrete structures which are curved or cornered in plan and have a cross-section which is either uniform or varies continuously or discontinuously with the height of the structure.

It is known that the arrangement and fixation as well as the supporting of the formwork for structures which are curved or cornered in plan and have a cross-section which is either uniform or varies continuously or discontinuously with the height of the structure involves considerable difficulties as the height of the structure to be erected increases. In view of the expenditure and the costs involved in the supports for the formwork it is practically impossible to provide a scaffold which grows in height with the structure. For instance in the erection of chimneys, high cooling towers, television transmitters or other slender structures it is not possible to provide a sufliciently stable outer scafiold extending throughout the height of the structure. To eliminate the need for an outer scaffold which grows with the structure to be erected it has been proposed to provide only an inner scaffold and to support diametrically opposite parts of the formwork on the inside of the structure, which formwork generally comprises known mold panels, against each other by means of struts which extend through the interior of the structure, and to connect the outer mold panels by means of racking or the like connections to the adjacent inner mold panels. If the formwork must perform sliding or climbing movements the connections extending through the finished concrete wall between the inner and outer mold panels are released and are renewed after the several panels have been moved. The location of the inner and outer mold panels on each other has the disadvantage, however, that a continuous sliding movement of the entire formwork is not possible because the release of all connections would deprive the outer formwork of any support. After encased sections of the structure have been completed the several panels must be successively released, displaced and re-a-ttached in their new position.

It has also been proposed to use a rope which is preferably provided with a turnbuckle and which embraces the entire outer formwork for retaining and supporting the outer mold panels. Such bracing ropes can only be used, however, for structures having the form of a circle or of a circular ring in cross-section because with structures having a different cross-sectional shape the rope would always tend to assume a circular form under-the formwork pressure. Even for buildings having a crosssectional shape of a circle or circular ring the use of bracing ropes of the proposed kind involves considerable difficulties because the vibratory movement for compacting the building material will inevitably cause a bulging out in the vibrated area.

Based on these recognitions it is an object of the invention so to construct a scaffold for supporting formwork that it is suitable for the erection of concrete structures of any desired plan shape and height and will prevent a deformation of the formwork even if it is not additionally supported on stationary abutments. I 3 To solve this object the scaffold for supporting formwork, particularly sliding or climbing molds for concrete structures which are curved or cornered in plan and the cross-section of which is either uniform or varies continuously or discontinuously with the height of the struc ture, is so constructed according to the invention that the scaffold has at least one closed tensile polygon of length-variable elements, which tensile polygon is formed as an abutment for rods which transmit the formwork pressure and are suitably at least partly variable in length and are disposed between the formwork and the tensile polygon.

, By the arrangement of closed tensile polygons consist ing of length-variable elements the pressure transmitted from the formwork to the tensile polygon is transformed in the case of the inner formwork into a compressive load acting on the closed tensile polygon and in the case of the outer formwork into a corresponding tensile load on the several elements forming the tensile polygon so that the load acting on the tensile polygon is uniformly distributed around the periphery thereof. The use of length-variable elements enables the adaptation of the tensile polygon to any cross-sectional shape of the building. Where similar scaffolds are used for the inner and outer formwork any desired cross-sectional shape and change thereof or may be provided for, with uniform or varying wall thickness. As the scaffold is directly connected to the formwork and extends only over the height of the formwork the scaffold and formwork can perform simultaneous sliding movements without need for separating the formwork from the scalfold.

To enable the scaffold to be adapted to the respective cross-section of the structure the length-variable rods are provided, which include in the static sense compressionresisting struts or tensile elements such as braces or the like. If only tensile stresses are to be encountered it is possible to use rope connections.

A simple and convenient construction of the scaffolding will be obtained if elements interconnected to form a tensile polygon and/or rods connected to the tensile polygon are at least partly tubular.

Scafiold elements consisting of elements or length-variable rods connected to form the tensile polygon consist suitably of spindles or of telescopic sections, preferably tubular sections. The spindles may be relatively robust to be suitable for the rough construction work. Telescopic sections, particularly tubular sections, are moved to and located in their respective relative positions e.g., by captive wedges or other setting means.

The formwork itself may consist or wood, preferably wooden panels, or of metallic mold panels, which compared to the wooden panels have the advantage that they can be adapted'to curvatures which correspond to different cross-sections of the structure. Such a formwork is preferably supported by length-variable struts or braces which are connected to the mold panels, preferably to their longitudinal edge stilfeners, and serve also for locating the panels in position.

Particularly for structure having a cross-section which varies with the height of the structure a particularly suitable construction of the formwork and scafiold can be obtained if the formwork consists at least in part of mold elements of relatively displaceable mold panels because in this case the scaffold and the formwork wall can be varied without addition or removal of parts, such as mold panels or braces, at least in certain height'ranges in spite of the varying cross-section of the building. Only the rods of the scaficld consisting of length-variable struts or braces must be connected at least in part to the relatively displaceable or pivoted mold panels of the formwork wall to locate the movable panels in position and, if desired, to move them, the rods being inclined relative to the normal on the formwork wall. The actua tion of the tightening means of predetermined rods and tensile polygon elements enables an adjustmentto different cross-sections of the structure so that cylindrical or conical structures or structures having a parabolic longitudinal section can be readily erected.

The scaffold may be simplified if at least one closed tensile polygon is equidistant with respect to the formwork wall. The arrangement of tensile polygons which are equidistant with respect to the formwork wall enables the use of similar elements and of similar rods for supporting the formwork wall so that the number of scaffold elements to be kept in stock is much reduced.

At least two tensile polygons are preferably provided to support one formwork wall and are suitably connected to or located by each other.

. The use of mold panels consisting of sheet metal members, which are to be preferred to a wooden formwork because relatively displaceable mold elements can be used, requires a stiffening of the formwork itself, e.g., by the arrangement of sections which are equidistant with respect to the mold surface. If such a formwork is used in conjunction with stiffeners the scaffold must be so arranged that the rods span the parts of the formwork at least in part as well as the intermediate stiifeners which are equidistant with respect to the formwork surface, and

that the rods consist preferably of elastically deformable sections, e.g., of spring steel strip and are secured to the longitudinal edge stiffeners of the formwork wall. To enable the formwork wall to envelop various cross-sections the stiffeners are preferably arranged to be longitudinally displaceable relative to the rods, e.g., by being guided in apertures of the rods or in clips connected to the longitudinal edge stiffeners.

The scaffold may also serve as a carrier for access scaffolds. In this case it is'suitable if formwork scaffold elements extending in the direction of the height of the structure, preferably rods serving to connect several tensile polygons, have a length which exceeds the distance between the tensile polygons to be connected so that the access scaffolds, consisting preferably of suspended scaffolds, can be secured thereto. The access scaffolds consist preferably also of tubular sections, in which the tubes serving as handrails extend parallel to the tensile polygons and are held unilaterally in the guide sleeve so that in the case of an adjustment of the scaffold to an increasing or decreasing cross-section of the structure the handrails slide in the sleeves. Additional tubes extending parallel to the rods serve in a manner known per se as supports for the access boards.

Further details of the invention will be explained with reference to the illustrative embodiments shown in the drawing.

FIG. 1 is a top plan view showing diagrammatically the formwork and the scaffolding of a hollow frusto-conical structureon two different levels.

FIG. 2 is an enlarged fragmentary view showing a part of the formwork and scaffolding of FIG. 1.

FIG. 3 is a sectional view taken on line III-III of FIG. 2 and showing a part of the formwork in elevation.

FIG. 4 is a vertical sectional view taken on line IV-IV of FIG. 2.

FIG. 5 is a sectional view showing a part of the outer formwork with an access scaffold afixed to the formwork scaffold.

In the righthand part of FIG. 1 the formwork and scaffold are shown which are disposed adjacent to a portion of the structure larger in diameter than in the left-hand part of this figure.

Specifically, 1 is the outer formwork wall and 2 is the inner formwork wall, which walls enclose between them the space 3 for the building materials to be filled in to form the wall of the structure. 4 are the length-variable elements of the outer tensile polygon, which are connected at the

joints

5 and 6. Struts 7 extending in a direction normal to the formwork wall are disposed between the joints 5 and the formwork wall 1 and struts or

braces

8 and 9 which are inclined relative to the rods 7 are disposed between the joints 5 and the formwork wall 1. The rods 7 are not provided with means for varying their length. The rods are pivoted to the formwork wall and to the joints. Rods 10 of adjustable length are provided as stiffeners between the joint 6 and the formwork wall 1. Like the outer formwork wall 1 the inner formwork wall 2 is supported against a closed tensile polygon consisting of length-variable elements 17. The formwork wall is supported by

rods

13 and 16 extending in a direction normal to the formwork wall and by braces or

struts

14 and 15 which extend diagonally like the

rods

8 and 9 of the outer scaffold. The tensile polygons consisting of the length-

variable elements

4 and 17, respectively, are equidistant with respect to the formwork wall. A variation of the length of the

elements

4 and 17 and of the

rods

8, 9 and 10 of the outer support and 14, 15, 16 of the inner support together with a simultaneous variation of the length of the formwork wall enables the formwork and scaffolding shown in the right-hand part of FIG. 1 to be transformed into the form shown in the left-hand part of the figure. The figure shows that the distance between the formwork and the tensile polygons has remained unchanged although the diameter of the structure has been reduced.

As is apparent from FIGS. 2 and 3 the formwork wall consists at least in part of mold elements consisting of relatively displaceable mold panels because in this case the formwork can be transformed from the diameter shown in the right-hand part of FIG. 1 to the smaller diameter shown in the left-hand part without need for removing parts of the formwork.

FIG. 2 shows a part of the arrangement diagrammatically represented in FIG. 1 and illustrates the construction and arrangement of the several formwork and scaffold elements. The figure shows again the length-

variable elements

4 and 17 of the outer and inner tensile polygons, respectively. The

rods

7, 8 and 9 are arranged between the joints 5 and the outer formwork wall consisting of the

elements

30, 31 and 32. The length-variable rods 10 are provided between the joints 6 and the formwork wall. The elements of the outer tensile polygon 4 are subdivided, provided with oppositely handed screw threads and guided in spindle nuts 20 so that the length of the elements 4 can be readily varied by a rotation of the spindle nuts 20. Similar in construction are the

rods

8, 9 and 10, which are provided with

spindle nuts

21, 22, 23. The

joints

5 and 6 of the outer tensile polygon are formed by the

vertical tubes

18 and 19. The construction and support of the inner tensile polygon agrees with that of the outer scaffold. The elements 17 are guided with screw-threaded portions in spindles 24. Each spindle 24 carries as a sliding fit a clip 28 to which the rod 13 is affixed. The clip '28 forms the joint indicated at 12 in FIG. 1.

Spindle nuts

25, 26, 27 are again provided for varying the length of the

rods

13, 14 and 15. Each of the joints 11 of the inner tensile polygon is formed by a vertical tube 11.

The construction of the formwork wall which consists of the differently shaped

elements

30, 31, 32 is apparent from FIGS. 2 and 3. The formwork consists of interconnected mold panels, namely, fixed mold panels 30, to which main mold panels 31 are connected, which serve as carriers for sliding mold panels 32. Each of the sliding mold panels 32 has another sliding mold panel 32 connected thereto, which is again guided in a main mold panel 31, which is again connected to a fixed mold panel 30. The several mold panels have longitudinally extending stiffeners. The fixed mold panel 30 has an intermediate stiffener 33 and side stifieners 34. The side stiffener 34 of the fixed mold panel 30 is connected to the side stiffener 35 of the main mold panel 31. The side stiffener 36 of the main mold panel 31 forms a guide slot for the sliding mold panel 32. The side stiffeners of the sliding mold panels 32 are again connected to each other v by clamps known per se so that the mold panels are forced against each other without gaps. As the mold panels are made from relatively easily deformable sheet metal, additional stifieners must be providedlaround the periphery thereof. These additional stiifeners must be elastically deformable so that the mold panel and the stifieners can be adjusted to the respective cross-sectional shape of the structure to be encased. In accordance therewith the stifieners'of the mold panels consist of

sections

39 and 40 of spring steel strip which'bear on the longitudinal edge stiir'eners and intermediatestiifeners of the mold panels. 'I hestifieners 39 are held by the

rods

7, 8 and 9. The stiifeners 40 are held by clips 42 which are so secured to the longitudinal edge stifieners 36 of the main mold panels 31 that the spring steel strip sections 40 can slide in the clips. The spring steel strip sections 39 are also guided in clips 41 aflixed to the longitudinal edge stitfeners '36 of the main mold panels 31 in such a mannerthat the stiifeners 39 can move laterally relative to the formwork wall in the case of a change in the radius of curvature of the formwork wall. The guidance of the stiifeners 39 in 'the fixing lugs '54 of the rods 7 is particularly clearly apparent from FIG. 5.

FIG. 4 illustrates the arrangement of FIG. 2 in a sectional view taken on line IVIV and shows that each formwork wall is supported by two interconnected tensile polygons. The rods 13 guided in the spindle nuts 25 are connected by the clips 28 to the spindle nut 24 whereas the rods 10 guided in the spindle nuts 21 are connected to the vertical tubes 18 forming the joints 6. The

rods

13 and 10 are "also supported against the longitudinal stiffeners 37 of the fixed mold panels 32. Instead of arshape of said mold wall to produce tension said polygonal structures.

2. A-framework for supporting a mold form wall, comprising, in combination, two polygonal structures spaced from each other, each polygonal structure including a plurality of elongated elements disposed in end to end re lation and having ends articulated to the ends of adjacent elements, a plurality of said elements including adjusting means for varying the length thereof; a plurality of connecting rod means connecting said two polygonal structures; a plurality of mold panels forming a continuous mold wall within said polygonal structures; and a plurality of strut means secured to each of said polygonal structures, at least the strut means secured to one of said polygonal structures including a strut extending substantially perpendicular to said mold wall and bracing rods inclined to said mold wall, said struts and bracing rods engaging said mold wall and supporting the same when the peripheral dimensions of said polygonal structures are adjusted by said adjusting means in accordance with the shape of said mold wall to produce tension in said polygonal structures.

3. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures spaced firom each other, each polygonal structure including a plurality of elongated'elements disposed in end to end relation and having ends articulated to the ends of adjacent elements, a plurality of said elements including adjusting means for varying the length thereof; a plurality ranging two tensile polygons 'for each formwork wall,

the latter' may be supported by a single tensile polygon if the

rods

10 or 13 are inclined. In this case the connecting tube 10 is omitted.

The construction of the formwork scafiold as a carrier of connecting rod means connecting said two polygonal structures; a plurality of mold panels forming a continuous mold wall within said polygonal structures; and

a plurality of strut means secured to each of said polygonal structures, at least the strut means secured to one of said polygonal structures including a strut extending substantially perpendicular to said mold wall and bracing rods inclined to said mold wall, said bracing rods including adjusting means for adjusting length thereof,

the tube 47 is provided, which extends parallel to the tube 19 and which is connected to the tube 19 by a bend disposed above the formwork scaffold. The

tubes

46 and 52

support access boards

51 and 53 so that two access scaffolds are provided, one of which consists of a suspended scaffold. Guide sleeves 48 affixed to the

tubes

47 and 19 carry the

handrails

49 and 50 for the two access scaffolds. The handrails consist of tubes extending parallel to the tensile polygons; They are fixed only at one end whereas the other end is slidable in the guide sleeves 48 so that the handrails can slide in the guide sleeves when the formwork 'scafiold is adjusted to a larger or smaller diameter.

What is claimed is:

1. A framework for supporting a mold form wall,

com-prising, in combination, two polygonal structures.

spaced from each other, each polygonal structure including a plurality of elongated elements disposed in end to end relation and having ends articulated to the ends of adjacent elements, a plurality of said elements including adjusting means for varying the length thereof; a plurality of connecting rod means connecting said two polygonal structures; a plurality of mold panelsforming'a continuous mold wall within said polygonal structures; and a plurality of strut means secured to each of said polygonal structures engaging said mold wall and supporting the same when the peripheral dimensions of said polygonal structures are adjusted by said adjusting means in accordance with the said strut and said bracing rods of each of said strut means being, pivotally connected to said one polygonal structure for pivotal movement about a common vertical axis, and having end-sengaging said mold wall at circumferentially spaced points and supporting the same when the peripheral dimensions of said polygonal structures are adjusted by said adjusting means in accordance with the shape of said mold wall to produce tension in said polygonal structures.

4. A framework for supporting a mold form wall,

comprising, in combination, two polygonal structures.

located in parallel planes, each polygonal structure including a plurality of elongated elements having adjusting means for varying the length thereof, said elongated elements being disposed in end to end relation and having ends articulated to the ends of adjacent elongated elements; a plurality of connecting rod'means connecting said polygonal structures; a plurality of mold panels forming a mold wall located within said polygonal structures; two sets of strut means secured to said polygonal structures, respectively, each of said strut means including a first strut. extending perpendicularto said mold wall, and bracing rods inclined tosaid mold wall, said first struts being of equal length, and said bracing rods including adjusting means for adjusting the length thereof; and second struts extending perpendicular to said mold wall secured to said polygonal structures alternating with said first struts and including adjusting means -for adjusting the length thereof, the ends of said first and second struts and of said bracing rods engaging circumferentially spaced points of said mold wall and supporting said mold wall when the peripheral dimensions of said polygonal structures are adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

5. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures loacted in parallel planes, each-polygonal structure including a plurality of elongated elements having adjusting means for'varying the length thereof, said elongated elements being disposed in endto end relation and having ends articulated to the ends of adjacent elongated elements; a plurality oflconnecting rod means connecting said polygonal structures; a plurality of mold panels forming a mold walllocated within said polygonal structures and having. a main axis;,two sets of strut means secured to said polygonal structures, respectively,'each of said strut means including a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equallength, and said bracing rod-s including adjusting means for adjusting the length thereof; a set of rods inclined to said axis, each rod connecting a first strut secured to one of polygonal structures .with a first strut connected to the other polygonal structure; and second struts extending perpendicular to said mold wall secured to said polygonal structures alternating with said first struts and including adjusting means for adjusting the length thereof, the ends of said first and second struts and of said bracing'rods engaging circumferentially spaced points of said mold wall and supporting said mold wall 'when the peripheral dimensions of said polygonal structures are adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

6. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures located in parallel planes, each polygonal structure including a plurality of elongated elements having two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts, said elongated elements being disposed in end to end relation and having ends articulated to the ends of adjacent elongated elements; a plurality of connecting rod means connecting said polygonal structures; a plurality of mold panels forming a mold wall located within said polygonal structures; two sets of strut means secured to said polygonal structures, respectively, each of said strut means including a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equal length, and said bracing rods including two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts; and second struts extending perpendicular to'said mold wall secured to said polygonal structures alternating with said first struts and including two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts, the ends of said first and second struts and of said bracing rods engaging circumferentially, spaced points of said mold wall and supporting said mold wall when the peripheral dimensions of said polygonal structures are adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

7. A framework for supporting a mold form wall, comprising, incombination, two polygonal structures located in parallel planes, each polygonal structure including a plurality of elongated elements having adjusting means for varying the length thereof, said elongated elements being disposed in end to end relation and having ends articulated to the ends of adjacent elongated elements and forming joints with the same; a plurality of connecting rod means. connecting said polygonal structures; a plurality, of mold panels forming a mold wall located within said polygonal structures; two sets of strut means pivotally connected to said joints of said polygonal strutcures,. respectively, each. of said strut ineansincluding a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equal length, and said bracing rods including adjusting means for adjusting the length thereof; and second struts extending-perpendicular to said mold wall secured to said polygonal structures alternat- .ing withsaid first struts and including adjusting means for adjusting the length thereof, the ends of said first and second struts and of said bracing rods engaging circumferentially spaced points of said mold wall and supporting said mold wall when the peripheral dimensions of said polygonal structures are adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

8. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures located in parallel planes, each polygonal structure including a plurality of elongated elements having two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts, said elongated elements being disposed in end to end relation and having ends articulated to the ends of adjacent elongated elements and forming joints with the same; a plurality of connecting rod means connecting said polygonal structures; a plurality of mold panels forming a mold wall located within said polygonal structures; two sets of strut means pivotally connected to said joints of said polygonal structures, respectively, each of said st-rut means including a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equal length, and said bracing rods including two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts; and second struts extending perpendicular to said mold wall secured to said polygonal structures alternating with said first struts and including two threaded parts threaded in opposite directions, and an adjustable nut connecting said threaded parts, the ends of said first and second struts and of said bracing rods engaging circumferentially spaced points of said mold wall and supporting said mold wall when the peripheral dimensions of said polygonal structures are adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

9. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures located in parallel planes, each polygonal structure including a plurality of elongated elements having adjusting means for varying the length thereof, said elongated elements being disposed in end-to end relation and having ends articulated to the ends of adjacent elongated elements and forming joints withv the same; a plurality of connecting rod means connecting said polygonal structures; a plurality of mold panels forming a mold wall located within said polygonal structures; steel band means abutting said mold panels; two sets of strut means pivotally connected to said joints of said polygonal structures, respectively, each of said strut means including a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equal length, and said bracing rods including adjusting means for adjusting the length thereof;

and second strut-s extending perpendicular to said mold wall secured to said polygonal structures alternating with said first struts and including adjusting means for adjusting the length thereof, the ends of said first and second struts and of said bracing rods engaging said steel band means on circumferentially spaced points and supporting said mold wallwhen the peripheral dimensions of said polygonal structuresare adjusted in accordance with the shape of said mold wall to produce tension in said polygonal structures.

10. A framework for supporting a mold form wall, comprising, in combination, two polygonal structures located in parallel planes, each polygonal structure including a plurality of elongated elements having adjusting means for varying the length thereof, said elongated elements being disposed in end to end relation and having ends articulated to the ends of adjacent elongated elements; a plurality of connecting rod means connecting said polygonal structures; including upright rods for within said polygonal structures; two sets of strut means 5 secured to said polygonal structures, respectively, each of said strut means including a first strut extending perpendicular to said mold wall, and bracing rods inclined to said mold wall, said first struts being of equal length, and said bracing rods including adjusting means for adjusting the length thereof; and second struts extending perpendicular to said mold Wall secured to said polygonal structures alternating with said first struts and including adjusting means for adjusting the length thereof, the ends of said first and second struts and of said bracing rods engaging ci-rcumferentially spaced points of said mold wall and supporting said mold wall when the pe- UNITED STATES PATENTS Brown Oct. 5, 1886 Weightrnan Mar. 14, 1905 Stieler June 5, 1917 Yeomans June 24, 1919 Stieler Aug. 11, 1925 Lamb Jan. 5, 1937 Lamb Ian. 21, 1947 Fiorenzi Jan. 1, 1952 Pratt Dec. 29, 1959 FOREIGN PATENTS Australia Feb. 21, 1950 France Mar. 18, 1953 Great Britain June 15, 1948 Great Britain Dec. 1, 1954