Formwork for casting a tubular structure

Abstract: The formwork assembly (10) is used to cast tubular or part-tubular structures, one particular application being in the lining of mine ore passes with a concrete lining (54). The assembly includes an internal framework (12, 14, 32; 100, 102, 104) and external, flexible formwork (34, 130) supported by the framework. The framework can be adjusted between a casting condition (Figure 1) in which it supports the formwork (34, 130) at the inner periphery of the structure which is to be cast and an inwardly collapsed condition in which it supports the formwork (34, 130) at a position spaced inwardly from such inner periphery. In the case of a mine ore pass lining, the assembly is moved upwardly in increments after each casting operation.

Description: BACKGROUND TO THE INVENTION This invention relates to a formwork assembly. In some underground mines, such as diamond and gold mines, ore passes are sunk from one level to another. Rock which has been mined at higher levels of the mine is dropped from one level to the next through the system of ore passes. At a low level in the mine, the ore is collected and possibly crushed before being transported to surface for further processing to recover the valuable mineral content thereof. The rock which has been tipped into and falls down the ore pass subjects the sides of the ore pass to severe impacts and it is therefore common to line the sides of the ore pass, usually with concrete. Conventionally, the concrete lining of an ore pass is constructed by assembling formwork, typically in a cylindrical shape, composed of rigidly interconnected shutters. The formwork is centrally supported a short distance from the bare, excavated walls of the ore pass. Wet concrete is poured between the shutters and the excavated walls and is allowed to set. After setting, the formwork assembly is disassembled and moved to a higher elevation for a repetition of the exercise. It will be appreciated that the repetitive assembly and disassembly of the formwork is time-consuming and labour intensive. DE-U-88 00 441.4 discloses a concrete hole plug for use in the formation of standard ceiling ducts during concreting, for heating, ventilation and plumbing pipes. The plug has a collapsible frame with a central support structure and a series of arms. Each arm has one end connected to the central support structure and an opposite end connected to a support member on which the formwork is carried. With this structure the assembly can be moved between an extended configuration in which the formwork is located at the inner periphery of the hole which is to be formed and a collapsed configuration in which central regions of the formwork are displaced inwardly, to allow removal of the assembly from the cast hole. The formwork consists of steel plates welded to support members in the form of pipes. SUMMARY OF THE INVENTION The present invention provides a formwork assembly comprising an internal framework and external formwork supported by the framework, wherein the internal framework includes a central support structure and a series of spokes each having one end connected to the central support structure and an opposite end connected to a support member, the formwork being attached to and supported by the support members and the spokes being connected to the central support structure and to the support members in pivotal fashion so as to be movable between an extended orientation in which the support members support the formwork at a casting position at the inner periphery of a structure which is to be cast and a collapsed orientation in which the support members support the formwork at a collapsed position spaced inwardly from the casting position, characterised in that the formwork comprises a flexible membrane which, in the casting position, defines a tubular or part-tubular shape against which a tubular or part-tubular inner periphery of the structure can be cast and which, in the collapsed position, assumes a folded configuration between the support members. In one version, the central support structure comprises a column, operatively upper spokes are pivotally connected to a sleeve which is slidable between stops on the column and operatively lower spokes are connected pivotally directly to the column, whereby initial pivotal movement of the spokes away from their casting orientation towards their collapsed orientation causes an operatively lower end of the flexible membrane to move inwardly prior to inward movement of the operatively upper end of the flexible membrane. The internal framework can be suspended on ropes, a ring being attached to the ropes and the column being movable relative to the ring. A screw jack mechanism is supported by the ring and is connected to the column to support the column relative to the ring, the screw jack mechanism being operable to raise and lower the column relative to the ring, thereby causing the spokes to pivot between the respective extended and collapsed orientations. In another version of the invention, the central support structure comprises spaced apart rings joined to one another by links, the rings and links surrounding a central space allowing access through the central support structure. In this version of the invention, double-acting hydraulic cylinders may be pivotally connected to the links and to the support members, the cylinders being extendable and contractible to cause the spokes to pivot between their respective orientations. The flexible membrane may define, in the casting position, a tubular surface against which the inner periphery of a tubular lining in a mine ore pass can be cast. The invention includes the use of a formwork assembly as above described for lining a mine ore pass with a cast concrete lining. Such use comprises: a) locating the flexible, tubular formwork at a casting position corresponding to the inner periphery of the desired ore pass lining; b) placing wet concrete behind the formwork and allowing the concrete to set to a predetermined level; c) inwardly collapsing the formwork and moving it axially to a new position higher up the ore pass; d) at the new position in the ore pass, outwardly expanding the formwork to locate it at the casting position; and e) repeating steps b) to d) as often as necessary to line the ore pass with a concrete lining. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which: Figure 1 illustrates, diagrammatically and partly in cross-section, a formwork assembly of the invention; Figure 2 shows a cross-section at the line 2-2 in Figure 1; Figure 3 illustrates the use of the formwork assembly of Figures 1 and 2 in the lining of an ore pass in a mine; Figure 4 illustrates, diagrammatically and partly in cross-section, a second version of formwork of the invention; and Figure 5 shows a cross-section at the line 5-5 in Figure 4. DESCRIPTION OF PREFERRED EMBODIMENTS With reference to Figures 1 and 2, a formwork assembly for use in the casting of a tubular structure, such as a concrete lining for an ore pass in a mine, is designated generally by the numeral 10. The assembly 10 includes a central column 12. A series of upper spokes 14 are attached at one end, by means of hinges 18, to a sleeve 20 which is able to slide up and down the column 12 between fixed collars 22 and 24. A corresponding series of lower spokes 16 are attached by hinges 26 to the lower end of the column 12. The spokes 14 and 16 are able to pivot individually in angularly spaced planes containing the column axis. The outer ends of the spokes 14 and 16 are attached by means of hinges 28 and 30 to upright supports 32 which are generally parallel to the column 12. Referring to Figure 2 in particular, it can be seen that the column 12, spokes 14 and 16 and supports 32 form a circular internal framework which is circumscribed by a tubular formwork membrane 34 of flexible material, in this case 45 mil (1,14mm) thick HYPALON (trade mark of E I Du Pont de Nemours & Co). The membrane is secured to the supports 32 by any suitable means. For instance, the membrane may be clamped to the members 32 by flat bars riveted, or otherwise secured, to those members. By pivoting the spokes 14 and 16 in upright planes relative to the column 12, the radial distance between the column 12 and the supports 32 is adjusted. Such adjustment varies the diameter and outer circumference of the circular internal framework. A reduction in the diameter of the framework causes the membrane 34 to be drawn inwardly towards the column 12, with the results that it folds or collapses in on itself in a festoon-like manner. The radial expansion and contraction of the internal framework is achieved by means of a screw jack mechanism indicated generally with the numeral 36. The mechanism 36 is mounted on a support ring 38 which is suspended on ropes 42 from an overhead support structure (not shown) that includes a winch or other means for raising and lowering the formwork assembly. It will be noted that the upper spokes 14 are suspended by ropes 40 from the support ring 38. The ropes 40 also assist in maintaining the angular spacing of the spokes 14. The mechanism 36 includes a jacking device having a frame 44 on the ring 38, a threaded aperture through the frame and a shaft 48 which extends in threaded fashion through the aperture and which is attached rotatably to the upper end of the column 12. A hand-wheel 46 is mounted fast on the upper end of the shaft 48. Rotation of the hand-wheel 46 raises or lowers the shaft 48 and column 12 relative to the ring 38, depending on the direction of rotation. Axial raising or lowering of the column 12 has the effect of altering the angles α and β defined between the column 12 and the spokes 14 and 16 respectively. In general, upward movement of the column 12 decreases the angles α and β, while downward movement increases them. Figure 3 illustrates the use of the apparatus described above in the casting of a concrete lining in an ore pass 50 excavated in a mine. The generally cylindrical wall of the ore pass is designated with the numeral 52 and a previous section of concrete lining with the numeral 54. The formwork assembly 10, suspended in the ore pass 50 by means of the ropes 42, is shown in the process of being relocated to a higher, as yet unlined section of the ore pass. In Figure 3, the internal framework is shown in a partially collapsed condition; this is achieved by rotating the hand-wheel 46 in a sense to raise the column 12 relative to the ring 38. When the hand-wheel 46 is first rotated in this sense, the angle β is immediately decreased. However, lost motion between the sleeve 20 and the column 12 allows the angle α to remain constant until such time as the collar 22 abuts the lower end of the sleeve and lifts it up. In the result, the lower ends of the supports 32, and accordingly the lower end of the membrane 34, are pulled away from the previously cast lining section 54 before the upper ends thereof. Withdrawing the membrane 34 from the set concrete in this way helps overcome vacuum effects which may exist between the membrane and the cast concrete. Once the membrane 34 has been withdrawn inwardly to a collapsed position clear of the previously cast concrete, the whole formwork assembly 10 is raised by means of the ropes 42 and the aforementioned winches or the like. The assembly is raised to a position in which the lower end of the membrane overlaps the previously cast concrete by a suitable margin of, say, 30cm. The handwheel 46 is then rotated in the sense to lower the column 12. The angles α and β are increased as the spokes 14 and 16 pivot upwardly relative to the column 12. Given the lost motion that takes place between the column 12 and the sleeve 20, it will be appreciated that the lower end of the membrane begins to move outwardly into position before the upper end of the membrane moves outwardly, the latter only occurring when the collar 24 abuts the upper end of the sleeve 20. With the membrane expanded to the appropriate position, the lower end thereof forms a seal against the upper end of the previously cast section of lining. Wet concrete can then be poured into the space 56 that is defined between the upper region of the membrane 34 and the wall 52 of the ore pass. The assembly 10 is left in this position for a period of time sufficient for the newly poured concrete to set to a self-supporting state, whereafter the assembly 10 is collapsed, raised and expanded again for the casting of the next higher section of the ore pass lining. Referring to Figure 2, it will be appreciated that the static pressure of the wet concrete acting on the membrane 34 will cause it to bow inwardly between the supports 32. The resultant, non-circular inner surface of the ore pass lining will, it is believed, assist in preventing rock hang-ups in the ore pass - this being a common problem in smooth walled ore passes. It will be appreciated that the column 12 and spokes 14 and 16 form a series of linkages which act in the manner of parallelogram linkages, with the exception that one corner in each such linkage has the facility both for pivotal and sliding movement, giving rise to the ability of the supports 32 to have orientations which are non-parallel to the column 12. Many variations are possible within the scope of the invention. For instance, instead of the illustrated, manually operated mechanism 36, hydraulic, pneumatic, electrical or other means can be employed. Figures 4 and 5 illustrate a hydraulically actuated formwork assembly of the invention. In this case, the central column is replaced by a central support structure consisting of upper and lower rings 100 and 102 and angularly spaced apart links 104 which are fixed at top and bottom to the upper and lower rings respectively. Although Figure 4 only illustrates one diametrically opposed pair of links, it will be apparent that there are many such links, angularly spaced apart from one another and extending between the upper and lower rings. Ropes 106 are connected to brackets 108 on the upper ring 100, the ropes extending upwardly to an overhead support structure (not shown) which includes the necessary winching apparatus for raising and lowering the apparatus. Once again, only two of the ropes are visible but there may in practice be many more ropes connected to the upper ring 100 at angularly spaced apart positions. Upper spokes 110 are pivotally connected at 112 to upright members 114 and at 116 to the upper ring 100. In similar fashion, lower spokes 118 are pivotally connected at 120 to the members 114 and at 122 to the lower ring 102. At each angular position, the spokes, central support structure and members 114 define a series of parallelogram linkages. Double acting hydraulic cylinders 124 are pivotally connected at points 126 to the members 114 and at points 128, adjacent the upper ring 100, to the links 104. The upright members 114 correspond to the members 32 of the first embodiment. A flexible membrane 130 is fastened to, and circumscribes these members. In full lines, Figure 4 shows the membrane in an expanded state with the spokes 110 and 118 virtually horizontal. The membrane is moved from the illustrated expanded state to a collapsed state by extending the hydraulic cylinders. Conversely, the membrane is moved from the collapsed state by contracting the cylinders. The cylinders can be operatively linked to one another to act in unison. One particular advantage of the embodiment of Figures 4 and 5 when compared to the first embodiment is the fact that the central support structure forms an open space 132 providing access from above the formwork apparatus to below it. Materials and men can pass up and down through the apparatus should this be necessary. Also, while the assembly 10 has been described in relation to the casting of a generally round cylindrical lining, it will be appreciated that other cross-sectional shapes are also possible with appropriate design of the internal framework and membrane. So, for instance, a formwork assembly of the invention can be used to line ore passes or other shafts having triangular, rectangular or other non-circular shapes. The invention has been described specifically in relation to the lining of a completely tubular ore pass, which will normally be vertical or nearly so. It is however anticipated that the principles of the invention could be used in the lining of horizontal tunnels or passages. In some cases, the lining which is cast may be only partially tubular, for instance in situations where the side and hanging walls only of a mine roadway or tunnel are lined. In cases where lining proceeds laterally, the formwork assembly could be conveyed in the appropriate direction by means of a vehicle.

Claims: A formwork assembly (10) comprising an internal framework (12, 14, 16, 32; 100, 102, 104, 110, 118) and external formwork (34, 130) supported by the framework, wherein the internal framework (12, 14, 16, 32; 100, 102, 104, 110, 118) includes a central support structure (12; 100, 102, 104) and a series of spokes (14, 16; 110, 118) each having one end connected to the central support structure (12; 100, 102, 104) and an opposite end connected to a support member (32; 114), the formwork (34, 130) being attached to and supported by the support members (32; 114) and the spokes (14, 16; 110, 118) being connected to the central support structure (12; 100, 102, 104) and to the support members (32, 114) in pivotal fashion so as to be movable between an extended orientation in which the support members (32, 114) support the formwork (34, 130) at a casting position at the inner periphery of a structure which is to be cast and a collapsed orientation in which the support members (32, 114) support the formwork (34, 130) at a collapsed position spaced inwardly from the casting position, characterised in that the formwork (34, 130) comprises a flexible membrane which, in the casting position, defines a tubular or part-tubular shape against which a tubular or part-tubular inner periphery of the structure can be cast and which, in the collapsed position, assumes a folded configuration between the support members (32; 114). A formwork assembly according to claim 1 characterised in that the central support structure comprises a column (12), operatively upper spokes (14) are pivotally connected to a sleeve (20) which is slidable between stops (22, 24) on the column and operatively lower spokes (16) are connected pivotally directly to the column, whereby initial pivotal movement of the spokes away from their casting orientation towards their collapsed orientation causes an operatively lower end of the flexible membrane (34) to move inwardly prior to inward movement of the operatively upper end of the flexible membrane. A formwork assembly according to claim 2 characterised in that the internal framework (12, 14, 16, 32) is suspended on ropes (42), a ring (38) is attached to the ropes, the column (12) is movable relative to the ring and a screw jack mechanism (36) is supported by the ring (38) and is connected to the column (12) to support the column (12) relative to the ring (38), the screw jack mechanism (36) being operable to raise and lower the column (12) relative to the ring (38) and thereby cause the spokes (14, 16) to pivot between their respective extended and collapsed orientations. A formwork assembly according to claim 1 characterised in that the central support structure comprises spaced apart rings (100, 102) joined to one another by links (104), the rings (100, 102) and links (104) surrounding a central space (132) that allows access through the central support structure. A formwork assembly according to claim 4 characterised in that double-acting hydraulic cylinders (124) are pivotally connected to the links (104) and to the support members (114), the cylinders (124) being extendable and contractible to cause the spokes (110, 118) to pivot between their respective orientations. A formwork assembly according to any one of the preceding claims characterised in that the flexible membrane (34, 130), in the casting position, defines a tubular surface against which the inner periphery of a tubular lining (54) in a mine ore pass can be cast. Use of a formwork assembly according to any one of the preceding claims for lining a mine ore pass with a cast concrete lining.

Inventors: SMUTS MICHIEL, SMUTS, MICHIEL
Applicants: DE BEERS IND DIAMOND, DE BEERS INDUSTRIAL DIAMOND DIVISION (PROPRIETARY) LIMITED
Application year: 1993
Main classification: E21D5
IPC codes: E04G15, E21D5