Field of the invention

The present invention relates to formwork which is to form part of poured concrete stairs, to a method of forming the stairs, and to the stairs formed by that method.

Background

Installation of a concrete stair flight typically comprises securing formwork to the lower floor area/landing and upper floor area/landing between which the flight is to extend, and erecting a temporary support structure, typically comprising scaffolding around the formwork, then pouring the concrete into the formwork (usually once stairway enforcing bar has been arranged therein) to form the steps of the flight. The temporary support structure is thereafter removed. Erecting and removing a temporary support structure such as scaffolding is time-consuming and labour-intensive. Also, the structure takes up space in an area that is often already restricted, such as a stairwell, and can thus hinder construction and pose a safety hazard.

Summary of the Invention

According to a first aspect of the present invention, there is provided formwork, for use in stairs to provide access between walking surfaces at different levels, installable such that a lower end thereof is at the lower of the levels and an upper end thereof is at the upper of the levels, and into which can be poured concrete, portions of which respective steps of the stairs are to comprise, wherein there is reinforcement to be secured or fixed at the upper end to a supportive or support structure which is to underlie or define the walking surface at the upper level, whereby the upper end is supported at the upper level, and/or secured or fixed at the lower end to a supportive or support structure which is to underlie or define the walking surface at the lower level, whereby the lower end is supported at the lower level (“securing reinforcement”). Preferably, the securing reinforcement comprises reinforcement for the poured concrete (“concrete reinforcement”), the concrete reinforcement being securable or fixable to the structure at either or each end whereby the securing reinforcement is so secured or fixed at that end.

Preferably, the securing reinforcement comprises one or more reinforcing members or bars securable or fixable to the structure at either or each end whereby the securing reinforcement is so secured or fixed at that end.

Preferably, the securing reinforcement is to be so secured or fixed at each of the upper and lower ends.

Preferably, the securing reinforcement is securable to the structure at either or each end by starter bars or reinforcing bars whereby it is so secured or fixed.

Preferably, the securing reinforcement is securable to a frame of which the structure is, or is to be, comprised at either or each end whereby it is so secured or fixed.

Preferably, the securing reinforcement is securable to a mesh of which the structure is, or is to be, comprised at either or each end whereby it is so secured or fixed.

Preferably, the securing reinforcement is securable to a frame of which the structure is, or is to be, comprised at either or each end whereby it is so secured or fixed.

According to a second aspect of the present invention there is provided formwork for use in stairs which is to provide access between walking surfaces at different levels, the formwork being configured such that a lower end thereof is to be supported at the lower of the levels and an upper end thereof is to be supported at the upper of the levels, and being reinforced such that, when the ends are so supported, it is self-supporting while concrete is poured into it to form steps of the stairs. Preferably, there is a cavity in said formwork, into which the concrete is to be poured. Preferably, the formwork includes a soffit.

Preferably, the cavity is bounded by the soffit.

The formwork of a preferred embodiment of the invention comprises spaced apart stringers which bound the cavity and between which the soffit extends, and spaced apart risers in the cavity, each of which is disposed over the soffit, extends between the stringers and forwardly bounds a respective void space arranged to receive a portion of the concrete poured into the formwork whereby there is formed a respective step of the stairs, comprising said riser and said portion, a tread of which step is defined by said portion.

The formwork of a preferred embodiment of the invention comprises spaced apart stringers which bound the cavity and between which the soffit extends, and spaced apart risers in the cavity, the risers comprising ones each of which is disposed over the soffit, extends between the stringers and forwardly bounds a respective void space arranged to receive a portion of the concrete poured into the formwork in the formation of a respective step of the stairs which comprises said riser and said portion.

Preferably, each stringer is formed from sheet material.

Preferably, each stringer comprises a side wall, bounding said cavity, and a flange projecting laterally inwardly from the side wall, to which a respective one of opposite side edges of the stringer is secured. Preferably, each laterally inwardly projecting flange underlies the respective side edge secured to it, thereby defining a shelf on which the soffit is supported.

Preferably, the soffit is configured in the form of a sheet.

Preferably, the formwork includes reinforcement to brace it against loads exerted by the poured concrete (“bracing reinforcement”). Preferably, the bracing reinforcement is to brace the soffit against loads exerted by the poured concrete. Preferably, the bracing reinforcement is secured to the soffit.

Preferably, the bracing reinforcement is to brace against bending loads of which said loads exerted by the poured concrete are comprised. Preferably, the bracing reinforcement is to brace against bending loads which are about a horizontal axis extending perpendicular to the stringers, of which said bending loads are comprised.

Preferably, the bracing reinforcement is arranged in the cavity.

Preferably, the bracing reinforcement comprises spaced apart ribs each of which extends between the lower and upper ends.

Preferably, each rib extends from the lower end to the upper end.

Preferably, each rib is configured in the form of a channel, having a base and opposed side walls projecting from the base, distal ends of the side walls being secured to the soffit. Preferably, each channel is configured with opposed flange portions each of which projects laterally outwardly from the distal end of a respective one of the side walls and is fixed against the soffit, whereby said distal ends are secured to the soffit.

Preferably, each rib is formed from sheet material.

Preferably, each riser is formed from sheet material. Preferably, each riser is secured at each of opposed ends thereof to a respective one of the stringers. Preferably, each riser is so secured whereby the stringers are braced by the risers against laterally inward deflection under loading exerted on the soffit by the poured concrete.

Preferably, a lower end of each riser and the soffit are interconnected. Preferably, the lower end of each riser and the soffit are so interconnected whereby the soffit is braced against bending loads, exerted by the poured concrete, about an axis extending parallel to the stringers.

Preferably, each riser comprises an upright wall, and ones of said upright walls forwardly bound respective ones of the void spaces. Preferably, the risers comprise ones each of which comprises a portion projecting rearwardly from an upper edge of the upright wall, whereby the upright wall and rearwardly projecting portion define nosing or capping at a front edge of the respective step. Preferably, the rearwardly projecting portion comprises a flange portion extending rearwardly from the upright wall upper edge, the nosing or capping being defined by that portion and said upright wall, and further comprises an anchor portion projecting downwardly from a rear edge of said flange portion, so as to be submerged in said portion of the poured concrete and thus retain the riser to said portion of the poured concrete.

Preferably, the anchor portion comprises a web portion extending downwardly from a rear edge of said flange portion, so as to retain the upright wall against said portion of the poured concrete.

Preferably, the anchor portion comprises a rearwardly projecting flange portion, so as to retain the nosing or capping, or the flange portion extending rearwardly from the upright wall upper edge, downwardly to said portion of the poured concrete.

Preferably, the rearwardly projecting flange portion extends from a lower edge of said web portion. Preferably, the risers comprise ones each of which comprises a toe portion projecting forwardly from a lower edge of the upright wall thereof, towards an upper end of the upright wall of a respective other one of the risers adjacent thereto in a direction from an uppermost/rearmost one of the risers to a lowermost/forwardmost one of the risers, the toe portion being arranged so as to be submerged in the portion of the concrete poured into a said void space forwardly bounded by the upright wall of said other riser, so as to retain the riser comprising that toe portion downwardly to that concrete.

Preferably, in the or each riser pair, comprising a respective one of the risers and a said other one of the risers adjacent thereto in said direction, the toe portion of said respective riser and the rearwardly projecting flange of said other riser define opposed respective ledges or shelves to support from beneath an underfoot element whereby said element defines a temporary platform structure on which an installer of the stairs can stand to perform tasks for completing the installation.

Preferably, in the or each riser pair, said respective riser is arranged such that the upright wall thereof restrains the underfoot element, supported by the ledges or shelves, against rearward movement.

Preferably, in the or each riser pair, said other riser is arranged such that the anchor portion, or said web portion thereof, restrains the underfoot element, supported by the ledges or shelves, against forward movement.

Preferably, said formwork is prefabricated for installation between said levels.

Said formwork according to a particularly preferred embodiment of the invention accords with both said first aspect and said second aspect.

Preferably, said securing reinforcement and said bracing reinforcement are arranged so as to interengage such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement. Preferably, the securing reinforcement is interlocked with said bracing reinforcement.

Preferably, the securing reinforcement is interconnected with said bracing reinforcement.

Preferably, the securing reinforcement extends through the bracing reinforcement.

Preferably, the or each reinforcing member or bar extends transverse to a direction from said lower end to said upper end.

Preferably, the or each reinforcing member or bar is arranged to be received through the bracing reinforcement.

Preferably, the bracing reinforcement is formed with one or more openings for receipt of the reinforcing member(s) or bar(s) therethrough.

Preferably, said reinforcing members or bars comprise ones axes of which are in alignment or substantially parallel. Preferably, said securing reinforcement is to be secured or fixed to the structure at either or each end via connective reinforcement.

In a preferred embodiment of the invention, the formwork is provided with said connective reinforcement connected to the securing reinforcement to secure or fix said securing reinforcement at either or each end.

In a preferred embodiment of the invention, the formwork is provided with said connective reinforcement and the securing reinforcement and connective reinforcement are arranged so as to interengage such that loading borne through either of the securing reinforcement and the connective reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement. Preferably, the formwork of either embodiment is provided with starter bars or reinforcing bars, of which said connective reinforcement is comprised, connected to the securing reinforcement.

Preferably, in the formwork of that embodiment said connective reinforcement extends from the securing reinforcement thereof.

The formwork of that embodiment may be installed such that the lower and upper ends are at the lower and upper levels respectively and the securing reinforcement is connected to reinforcement of which the support structure is, or is to be, comprised at either or each end, such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.. Preferably, in the formwork of that embodiment, the securing reinforcement is connected, via said connective reinforcement, to reinforcement of concrete of which the support structure is, or is to be, further comprised at either or each end.

Preferably, the securing reinforcement and connective reinforcement interengage or are interconnected such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

Preferably, the connective reinforcement and the reinforcement of which the support structure is, or is to be, comprised at either or each end interengage or are interconnected such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

The formwork of that embodiment may be such that said concrete can be, or has been, poured thereinto. According to a third aspect of the present invention, there is provided an assembly comprising said formwork and reinforcement of which the support structure is, or is to be, comprised at either or each end, wherein the formwork is installed such that the lower and upper ends are at the lower and upper levels respectively and the securing reinforcement is connected to the reinforcement of which the support structure is, or is to be, comprised at either or each end, such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

According to a fourth aspect of the present invention, there is provided an assembly comprising said formwork and said connective reinforcement, wherein said connective reinforcement is connected to the securing reinforcement to secure or fix said securing reinforcement at either or each end.

According to a fifth aspect of the present invention, there is provided an assembly comprising said formwork and said connective reinforcement, wherein the securing reinforcement and connective reinforcement interengage or are interconnected such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

According to a sixth aspect of the present invention, there is provided an assembly comprising said formwork, said connective reinforcement and the reinforcement of which the support structure is, or is to be, comprised at either or each end, wherein the former and the latter reinforcement are interconnected or interengage such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

Preferably, the connective reinforcement comprises starter bars or reinforcing bars connected to the securing reinforcement.

Preferably, said connective reinforcement extends from the securing reinforcement. Preferably, the lower and upper ends are at the lower and upper levels respectively and the securing reinforcement is connected to reinforcement of which the support structure is, or is to be, comprised at either or each end, such that loading borne through either reinforcement, resulting from loading against which it provides reinforcement, is transferred to the other reinforcement.

Preferably, said assembly comprises reinforcement of which said structure at either or each level is, or is to be, comprised, and the formwork is installed such that the lower and upper ends are at the lower and upper levels respectively and connected to that reinforcement via said connective reinforcement is the securing reinforcement at either or each end.

Preferably, the securing reinforcement is connected, via said connective reinforcement, to reinforcement of or for concrete of which the support structure is, or is to be, further comprised at either or each end.

The assembly may be such that into the formwork thereof can be poured said concrete.

The assembly may be such that concrete of which the support structure at either or each level is to be comprised is pourable thereinto.

The assembly may be such that into it is pourable, at said upper level, concrete whereby the concrete to be poured into said formwork is so poured and the concrete of which the support structure at either or each level is to be comprised is poured.

The assembly may include concrete, poured at said upper level, whereby to comprise said concrete poured into said formwork and the poured concrete of the support structure at either or each level.

According to a seventh aspect of the present invention, there is provided a stair installation method comprising pouring into formwork which accords with the second aspect said concrete, wherein said formwork is supported, at the lower and upper ends thereof, at the lower and upper levels respectively, so as to be self-supporting during the pouring.

According to an eighth aspect of the present invention, there is provided a stair installation method in which there is provided formwork which accords with the second aspect, wherein said concrete is poured into the formwork to form, or in the formation of, said steps, the lower end of the formwork being supported at the lower of the levels and the upper end of the formwork being supported at the upper of the levels, whereby the formwork is self- supporting during the pouring.

A preferred embodiment of the method of the eighth aspect accords with the seventh aspect.

According to a ninth aspect of the present invention, there is provided a stair installation method wherein formwork according to the first aspect is installed such that the lower end thereof is at the lower level and the upper end is at the upper level, and wherein said securing reinforcement is secured or fixed at the upper end to the structure at the upper level or reinforcement of which the structure at the upper level is or is to be comprised, whereby the upper end is supported at the upper level, and/or secured or fixed at the lower end to the structure at the lower level or reinforcement of which the structure at the lower level is or is to be comprised, whereby the lower end is supported at the lower level, the method comprising pouring into the installed formwork said concrete wherein there is reinforcement to be (“securing reinforcement”).

Preferably, in the method of the ninth aspect, said securing reinforcement is secured or fixed via said connective reinforcement to the structure at either or each of the upper and lower level or reinforcement of which that structure is or is to be comprised.

Preferably, the method of the ninth aspect includes correctly positioning the formwork relative to the upper and lower levels and thereafter effecting connection of the connective reinforcement between the formwork and the reinforcement of which the structure at either or each level is or is to be comprised, whereby the formwork is so installed, and wherein effecting said connection of the connective reinforcement comprises positioning the connecting reinforcement relative to the securing reinforcement during attachment of the former to the latter, such that the connective reinforcement is located appropriately for connection to the reinforcement of which the structure at either or each level is or is to be comprised, and effecting the connection of the connective reinforcement, so located, to the reinforcement of which the structure at either or each level is or is to be comprised.

A preferred embodiment of the method of the ninth aspect accords with either or each of the seventh and eighth aspects.

According to a tenth aspect of the present invention, there is provided the stair(s) installed by a method according to any one of the seventh, eighth and ninth aspects.

The walking surface at either or each of the levels may be a floor surface, or instead defined by a platform such as a balcony or deck. In either case, the end of the formwork supported at that level may be fixed to supportive structure underlying or defining that walking surface, which structure may comprise, for example, a frame or slab. Another possibility is that the walking surface is defined by an area of ground, in which case the end of the formwork supported at the level comprising that area of ground may be fixed to/supported from the ground.

Brief Description of the Drawings

Embodiments of the present invention will now be described, by way of non-limiting example only, with reference to the accompany drawings, in which:

Figure 1 shows poured concrete stairs;

Figure 2 shows an installed formwork to form part of the stairs according to a first preferred embodiment of the invention;

Figure 3 is disassembled partially exploded view of the formwork according to the first embodiment;

Figure 4 is a partially exploded detail view showing risers and reinforcing elements of the formwork according to the first embodiment; Figure 5 is a front elevation view of the formwork according to the first embodiment;

Figure 6 is a side cross-sectional view through section 6-6 of Figure 5;

Figure 7 shows detail 7 designated in Figure 6;

Figures 8 and 9 are engineering drawings comprising a side view of the formwork according to the first embodiment and a cross-sectional view through section A-A therein, respectively;

Figures 10 and 11 are perspective and side elevation views, respectively, of one of the risers;

Figure 12 shows poured concrete stairs having a lower end resting on, or otherwise arranged over, a lower walking surface and including formwork in accordance with a variant of any one of the embodiments illustrated in and described herein with reference to the other drawings, this variant itself being a preferred embodiment of the invention;

Figure 13 is a partially exploded detail view showing details of formwork for forming stairs, including risers and reinforcing elements and crossmembers of that formwork, in accordance with a second preferred embodiment of the invention;

Figure 14 is a side cross-sectional view of the formwork/stairs of the second embodiment, corresponding to Figure 6;

Figure 15 shows detail 15 designated in Figure 14;

Figures 16 and 17 show successive stages in the installation of the stairs according to the second embodiment;

Figure 18 shows stairs comprising prefabricated formwork in accordance with a preferred embodiment of the invention according to a variant of any one of the embodiments illustrated in and described herein with reference to the other drawings, this variant itself being a preferred embodiment of the invention;

Figure 19 is a perspective view showing details of the upper end of formwork to form part of poured concrete stairs according to a variant of any one of the embodiments illustrated in and described herein with reference to the other drawings, this variant itself being a preferred embodiment of the invention;

Figure 20 is a side elevation view showing details of the upper end of the formwork of the variant mentioned in the above description of Figure 19; and

Figure 21 shows the use of at least one underfoot element, such as a plank or tray, to form a temporary platform structure which facilitates the installation/formation of the stairs in accordance with any one of the preferred embodiments.

Detailed Description

The content of Australian provisional patent application no. 2018903561, filed 21 September 2018, is incorporated herein by reference in its entirety.

Shown in Figure 1 are stairs 100 installed, between a lower level 2 and an upper level 3, in accordance with a first preferred embodiment of the present invention. The stairs 100 comprise formwork 1 and concrete 11 which has been poured into and allowed to set within the formwork 1.

The formwork 1 of the first embodiment, referring to Figures 2, 8 and 9, is prefabricated and comprises opposed stringers 4, each of which (as shown in Figures 4 and 9) is folded from metal (preferably steel) sheet, so as to be configured at a lower edge thereof with an inwardly projecting flange 4 A, and at an upper edge thereof with a doubled over portion defining a rim 4B (which is blunt compared to the edge of the sheet in the doubled over portion). The formwork 1 further comprises a soffit 8, formed from the same sheet material, which sits on the flanges 4A and is secured (e.g. welded, screwed, riveted) to them, so as to define a floor of the formwork 1.

The formwork 1 includes bracing reinforcement in the form of laterally spaced apart inverted channels 9, which are secured to the soffit 8 and extend, parallel to the stringers 4, substantially the length of the soffit 8. Each channel 9 is cold rolled, again from the same sheet material, and comprises (referring to Figures 4 and 9) a base or web 9A, side walls 9B projecting from opposite edges of the base 9A, and flanges 9C each of which projects laterally outwardly from a distal edge of a respective one of the side walls 9B for receipt against the upper surface of the soffit 8. Each channel 9 is secured to the soffit 8 by clinching the flanges 9C thereof and soffit 8 together. The number of laterally spaced channels 9 may vary without departure from the invention. In alternative embodiments, there may be multiple inner channels 9. The formwork 1 additionally comprises, referring to Figures 2 to 4, 10 and 11, risers 5 arranged at regular intervals along the length of the formwork 1, each riser 5 being likewise rolled/formed from the same sheet material and (as can best be seen at Figures 10 and 11) comprises an upright wall 5A, atoe 5B projecting forwardly from a lower edge of wall 5A, and a z-shaped portion which extends rearwardly from the upper edge of the wall 5 A, the z-shaped portion comprising a flange portion 5C projecting rearwardly from that edge, a web portion 5D, projecting downwardly from a distal edge of the flange portion 5C, and a flange portion or flange 5E projecting rearwardly from a lower edge of the web portion 5D.

Each riser 5 is arranged such that the lower end thereof is supported against, and if appropriate attached to, each of the channel webs 9A whereby the toe 5B thereof projects forwardly and substantially horizontally, the opposite ends of each riser 5 being secured (e.g. welded, screwed, riveted) to respective stringers 4. Alternatively, the risers 5 may not contact the channels 9 and may instead be suspended clear of them by their attachment at each end to the stringers 4. The spacing of the risers 5 is such that the flange 5E of each except the uppermost/rearmost riser 5 is at substantially the same level as the toe 5B of a riser 5 adjacent to it in a direction from the forward/lower end of the formwork 1 to the rearward/upper end of the formwork 1. The uppermost/rearmost riser 5 is positioned such that the portion 5C thereof is flush with/at the same level as the floor/walking surface of the upper level 3.

The formwork 1 advantageously, is lightweight (owing to its comprising components formed from sheet) while being strong enough to be, when supported/secured at its upper/rear and lower/front ends to the levels 3 and 2 respectively (or otherwise supported therefrom), self-supporting throughout the pouring of the concrete 11 therein, whereby temporary support, such as scaffolding, is unnecessary. If necessary/appropriate, reinforcement for the concrete - typically comprising reinforcing bars/reinforcing steel - may be arranged in the formwork 1 prior to pouring of the concrete 11. Starter bars (not shown) may be used to secure the formwork against a face 3 A defined by an edge of a support structure (e.g. floor structure or landing) underlying or defining the upper walking surface 3, as shown in Figure 1, such starter bars, which are conventionally reinforcing steel and more particularly rebar, thus defining connective reinforcement. At the lower end, the formwork may be secured at, or to a face defined by, an edge of a support structure (e.g. floor structure or landing) underlying or defining the lower walking surface 2 by way of starter bars, analogous to how the formwork is secured to the upper walking surface 3, as shown in Figure 1, such starter bars, conventionally reinforcing steel and more particularly rebar as mentioned above, likewise thus defining connective reinforcement. In an alternative arrangement embodying the invention, the stringers 4 and soffit 8 may be supported on the lower walking surface 2 with a terminal riser bounding the formwork, in which case the stairs would have the appearance shown in Figure 12.

The concrete 11 when poured occupies elongate recesses 10 (indicated in Figures 2, 4, 5 and 9), which comprise laterally outer recesses 10 each defined between a respective laterally outer one of the channels 9 and stringer 4 adjacent to it. Alternatively, the pouring of the concrete may be such that it does not occupy the recesses 10 - for example, a partition (e.g. a sheet) may be arranged over the channels 9 to preclude filling of the recesses 10 with concrete, or lightweight filling material, e.g. foam or wood, which may be in the form of blocks or particulate, could be used to fill the recesses 10 prior to pouring of the concrete 11, whereby the weight of the stair flight is less.

The concrete 11 is poured, all in a single action, to the extent that void spaces 12 (shown in Figure 2), which overlie the recesses 10, are filled therewith, each void space 12 being bounded at a front thereof by a respective riser 5 and at each side thereof by a respective one of the stringers 4, an upper end of the void space 12 being substantially flush with the flange portion 5C of that riser. Thus, the web portion 5D and flange 5E are submerged in the poured concrete so as to be embedded in that concrete when it has set. Because the flange 5E of each except the uppermost/rearmost riser 5 is at substantially the same level as the toe 5B of a riser 5 adjacent to it in a direction from the forward/lower end of the formwork 1 to the rearward/upper end of the formwork 1, that toe is also submerged in the poured concrete so as to be embedded in that concrete when it has set. Advantageously, the toe 5B thus downwardly retains the riser 5 which comprises it, especially the upright wall 5 A thereof, to that concrete, and the lower end portion of the upright wall 5A which is likewise submerged/embedded in that concrete retains the riser 5 to the concrete to the other side of the upright wall 5.

The flange portion 5C can, advantageously, serve as a marker of the upper end of the void 12 bounded at the front by that flange portion, and thus the level to which the concrete 11 is to be poured in the formation of a respective step 13 of the flight. Advantageously, the upright wall upper end and flange portion 5C define nosing or capping at a front edge of the respective step, which protects the concrete edge which it overlies. Advantageously, owing to the z-section portion defined by flange portion 5C, web portion 5D and flange 5E, the upper end of each riser 5 is securely anchored to/at the front of the respective step 13. In particular, the rearwardly projecting flange portion 5E retains the nosing/capping, especially the flange portion 5C, downwardly to the concrete, and the web portion 5D retains the upright wall 5A/nosing/capping horizontally to the concrete.

Shown in Figures 16 and 17 is installation of stairs 100', which include formwork G, in accordance with a second preferred embodiment of the present invention. In the description of, and drawings for, this embodiment, reference numerals as have been used in respect of the previous embodiment, will be used to denote and refer to the same or corresponding features. The formwork G, referring to Figures 13 to 15, is identical to the formwork 1 with the exception that it includes securing reinforcement comprising concrete reinforcing bar (rebar) cross-members 20, at the forward/lower end and rearward/upper end thereof and the channels 9 are configured with openings/holes 9D, through sidewalls 9B thereof, through which respective ones of the cross-members 20 extend, such that the cross-members 20 and channels 9 are interconnected. The cross-members 20 may be welded or otherwise secured to the channels 9 and/or either/each of the stringers 4 to which opposed ends thereof are adjacent, so as to be affixed along their axes relative to the channels 9. The cross- members 20 define connection points via which the upper/rear and lower/front ends of the formwork are to be secured to floor/underfoot structures at the levels 3 and 2 respectively, as will be apparent from the forthcoming description. In the case of the present embodiment, each end of the formwork G is to be secured at an edge of the support structure (e.g. floor structure or landing) which underlies the walking surface adjacent that end, consistent with Figure 1.

In the installation of the stairs 100', the floor/underfoot structure at each level is to comprise reinforced concrete, and securing of the ends of the formwork G at the upper and lower levels precedes pouring of that concrete. Specifically, starter or reinforcing bars 30A are secured between the cross-members 20 at the upper end (“upper cross-members”) and reinforcing steel, comprising reinforcing bar/mesh 40A, at the upper level 3 which is to reinforce the concrete that has yet to be poured at/to occupy that level, and starter or reinforcing bars 30B are secured between the cross-members 20 at the lower end (“lower cross-members”) and reinforcing steel, comprising reinforcing bar/mesh 40B, at the lower level 2 which is to reinforce the concrete that has yet to be poured at/to occupy that level. The mesh 40A and mesh 40B define respective frames to be submerged/embedded in the concrete to be poured, typically so as to form a slab, at the upper and lower levels 3,2 respectively, thus reinforcing that concrete. At each level, there is thus formed a supportive structure, comprising the mesh and the concrete poured at that level, which is to underlie or define the walking surface at that level. More particularly, forward/lower end sections 30A1 of the bars 30A are connected to the upper cross-members 20 (e.g. by welding and/or lashing/tying with metal wire, and/or by any other suitable reinforcement connections as would be known to a person skilled in the art) and rearward/upper end sections 30A2 of the bars 30A are connected (in a like manner) to the reinforcing bar/mesh 40A, and rearward/upper end sections 30B1 of the bars 30B are connected to the lower cross-members 20 (also in a like manner) and forward/lower end sections 30B2 of the bars 30B are connected (also in a like manner) to the reinforcing bar/mesh 40B. The end sections 30A2 and 30B2 extend generally horizontally to be connected to the reinforcement 40A and 40B respectively, whereas the end sections 30A1 and 30B1 are inclined, to the same extent as the stairs, to be connected to the upper and lower cross-members 20 respectively.

The connection of the bars 30 between the formwork G and reinforcement 40A and 40B at the upper and lower levels 3 and 2 is effected after the formwork G is correctly positioned relative to those levels whereby, advantageously, it is ensured that the positioning of the bars 30A/30B relative to the cross-members 20, during attachment of the former to the latter, is such that the bars 30 are located appropriately for connection to respective sections of the reinforcement 40 A and 40B.

Arranged at the upper and lower levels 3, 2 is formwork and/or shuttering 60A and 60B respectively, to contain at the upper level 3 the concrete poured to occupy/form part of the structure at that level, and to contain at the lower level 2 the concrete poured to occupy/form part of the structure at that level, respectively. Advantageously, pourable at the upper level 3 is concrete whereby the concrete to be poured into said formwork (11) is so poured and the concrete of which the support structure at either or each level is to be comprised is poured.

Advantageously, owing to the resulting interconnection between the reinforcement (including the cross-members 20) of the formwork and the reinforcement 40A and 40B at the upper 3 and lower 2 levels, via the connective concrete reinforcement defined by/comprised of the bars 30 (30A and 30B), the securement of the formwork G and thus the stairs 100' to the floor/underfoot structure at each of the levels is uncomplicated, both in form and to effect, is particularly strong and also particularly robust, including to/against loads caused by earth tremors or earthquakes. The interconnectedness or contiguity of the reinforcement in each of the upper and lower levels and the bracing reinforcement in the formwork, owing to the connecting bridge therebetween defined by the members 20 and starter/reinforcing bars connected to them, affords the entire structure, comprising the upper and lower floor/underfoot structures and the stairs therebetween, excellent structural integrity and robustness.

Without departure from the invention, it may be only one of the upper/rear and lower/front ends of the formwork which is to be provided with cross-members 20 for securement thereof to reinforcement 40 at the level adjacent that end; for example, it may be that said one end is the upper end and that said lower end is essentially supported on, or otherwise positioned over, the walking surface at the lower level 2, in which case the appearance of the stairs would be as shown in Figure 12. Even in an embodiment, shown in Figure 18, which is such that the lower end of the stairs/formwork is so supported/positioned (and regardless of whether or not, in that embodiment, there are provided upper cross-members 20 and connections, comprising bars 30 A, between those cross-members and reinforcement 40 A), there may be provided the lower cross-members 20 and provided also connections between those cross-members and reinforcement 40A, these connections comprising starter or reinforcing bars 30' upper/rearward end sections 30BG of which are connected to the lower cross-members 20 (e.g. by welding and/or lashing/tying with metal wire, and/or by any other suitable reinforcement connections as would be known to a person skilled in the art) and lower/forward end sections 30B2’ of which are connected (in a like manner) to the reinforcement 40B, those lower/forward end sections extending downwards to be connected to the reinforcement 40B (unlike the end sections 30B2, which extend generally horizontally to be so connected). The end sections 30BG are inclined, to the same extent as the stairs, to be connected to the lower cross-members 20. The bars 30' in this embodiment define the connective concrete reinforcement at the lower end.

As will be clear from the foregoing, the configuration of either or each of the upper and lower ends of the formwork, as well as the configuration of the structure to which that end connects at the upper/lower level, can vary without departure from the invention. Shown in Figures 19 and 20 are details of the upper end of the formwork 1”, and the upper level to which that end is secured, which accords, without departure from the invention, with a variant of any one of the embodiments illustrated in, and described above with reference to, the other drawings. In the case of this variant, each of the stringers 4” is formed, at the upper end thereof, with an upright, rearwardly facing edge 4C and a substantially horizontal, upwardly facing edge 4D, arranged to abut, or be received adjacent to and in alignment with, face 3 A and an underside face 3B of the edge of the support structure (e.g. floor structure or landing) underlying or defining the upper walking surface 3, respectively, or bounding laterally concrete which has been poured into the formwork and occupies the upper end of the formwork and which is integral with concrete poured at the upper level 3 to form part of said support structure. The uppermost/rearmost riser 5 in the formwork 1” of this embodiment is arranged to lie adjacent the outermost extent of said support structure. The formwork 1” may be configured with a generally horizontally projecting flange portion 4E which extends between the stringers 4” and projects rearwardly therefrom in general alignment with edges 4D so as to be received against/give rise to underside face 3B, and which may be secured against that face by fasteners (not shown). The formwork 1”, without departure from the invention, may include the upper cross-members 20, provided in holes 9D, as shown in Figure 20, or may be instead not include those cross-members/be configured with those holes, as shown in Figure 19.

Referring to Figure 21, in the case of any one of the embodiments described above with reference to the drawings, the flange 5E of each of the risers 5 adjacent to which there is another riser 5 in a direction from the forward/lower end of the formwork, and the toe 5B of that adjacent riser 5, define shelves to support a respective underfoot element 50, such as a plank or tray, to form a temporary platform structure, on which an installer of the stairs may stand, including before, during and/or after pouring of the concrete into the formwork, to perform tasks for the purposes of completing the installation, including evenly distributing the concrete poured into the formwork therewithin, the/each element 50 being retained in a forwards-rearwards direction by the web portion 5D from which the flange 5E projects and the upright wall 5 A from which the toe 5B of the adjacent riser 5 projects. The elements 50 may be retained laterally by the opposed stringers, if of a length sufficient that opposed lateral edges thereof abut those stringers.

While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.