TECHNICAL FIELD

This invention relates to formwork apparatus for the construction of stairs. In particular, the invention relates to a stair riser forming apparatus that incorporates extendable and angularly adjustable components and couplings which can be used to form a range of stair widths and stair riser (or step) heights.

BACKGROUND

A significant problem in the construction of concrete stairs is waste associated with the conventional formwork that is used when forming-up the stairs. There is considerable material wastage in the off cuts of wood and other wood based materials (such as plywood) that are left over after pieces have been cut to a desired size and shape to suit the space into which the stairs are to be constructed.

Conventionally, it has been a labour intensive, time consuming and costly task to create a range of separate, non-reusable, wood based formwork components that need to be measured, cut out and nailed together. The wood based formwork components created and used in this way are rendered redundant after each use, and must also be disposed of as waste.

It is an object of this invention to provide formwork apparatus that does not create such waste and is quick and easy to use.

It is a further object of this invention to provide a length adjustable formwork apparatus that can be re-used.

SUMMARY OF INVENTION

According to the present invention, there is provided a formwork apparatus for constructing concrete stairs, the formwork apparatus comprising a left side extender arm and a right side extender arm, each of which are slidably connected to a bridging connector which spans the extender arms so as to form a length adjustable waler structure of the formwork apparatus, whereby the extender arms can be engaged against a riser board cut to an appropriate length and height for each step of the stairs being constructed.

In a preferred form, a left end anchor plate is adjustably connected to a left end of the left side extender arm, and a right end anchor plate is adjustably connected to a right end of the right side extender arm, wherein said adjustable connection of the anchor plates allows for a perpendicular adjustment of the distance that each anchor plate can be moved away from the end of its respective extender arm, and also allows for an angular adjustment of each anchor plate, whereby the anchor plates can be engaged against upright surfaces which are either vertical or not vertical at opposite sides of the stairs being constructed.

Preferably, the left and right side extender arms each have upper and lower flange portions with inner surfaces which are configured to engage and press against the riser board.

It is preferred that the left and right side extender arms each have a central channel portion with male outer surfaces which are configured to mateably engage within, and be tightened and loosened against, female inner surfaces of a main channel portion of the bridging connector.

In another preferred form, the left and right side extender arms can each individually slide relative to the bridging connector via the engagement of the respective central channel portion of the extender arm with the main channel portion of the bridging connector.

The anchor plates preferably have mirror image structures comprising a flat main panel and a connector bracket secured to an inner side of the main panel, the main panel having apertures at predetermined locations that allow for direct securing by fasteners of the main panels to the upright surfaces at opposite sides of the stairs being constructed.

The connector bracket preferably has a top panel, the top panel having an upper elongated slot for receiving an upper bolt, and there is an upper threaded opening for screwably engaging the upper bolt at an outer end of a top part of the central channel portion of each extender arm.

The connector bracket preferably also has a side panel, the side panel having a lower elongated slot for receiving a lower bolt, and there is a lower threaded opening for screwably engaging the lower bolt at an outer end of the male outer surfaces of the central channel portion of each extender arm.

It is preferred that the upper and lower elongated slots each have a direction of elongation which allows for the perpendicular adjustment of the distance that each anchor plate can be moved away from the end of its respective extender arm, and which allows for the angular adjustment of each anchor plate.

The lower bolt preferably provides a horizontal axis of rotation to allow for the angular adjustment of the anchor plate to a desired non-vertical angle, and the so angularly adjusted connection of the anchor plate with its extender arm is maintained by firstly inserting the upper bolt through the upper elongated slot of the top panel and then by screwably engaging the upper bolt in the upper threaded opening of the extender arm.

In yet another preferred form, the bridging connector has stop holes which are symmetrically located on either side of the middle of the bridging connector, and the stop holes identify a maximum extended length beyond which one or both of the extender arms should not be slid away from each other, whereby the formwork apparatus can be extended to a desired length corresponding to a length of the riser board.

The upper and lower flange portions of each extender arm may have holes formed at predetermined locations therealong for receiving screws to secure the formwork apparatus against the riser board.

In a still further preferred form, the bridging connector has an upper channel portion connected to the main channel portion, and within the upper channel portion are a series of spaced apart nuts, top and bottom openings of each nut being aligned with similarly sized openings in top and bottom parts of the upper channel portion, and a top part of the central channel portion of the extender arm, over which slides the bottom part of the upper channel portion of the bridging connector, does not have any similarly sized openings, such that when each nut is screwably engaged by a bolt which passes through the openings in the top and bottom parts of the upper channel portion of the bridging connector, a tip of the bolt will press down on the top part of the central channel portion of the extender arm, whereby there is a tight clamping together of the bridging connector and the extender arms.

It is preferred that the left and right side extender arms and the bridging connector are made of metal, and that the left and right end anchor plates are also made of metal.

The metal is ideally selected from the group consisting of steel, mild steel, stainless steel, and aluminium, although any other suitable metal or metal alloy or composite material with the required strength and other structural and functional properties may be used. There has been thus outlined, rather broadly, the more important features of one aspect of the invention in order that the detailed description thereof that follows may be better understood and put into practical effect, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter. As such, those skilled in the art will appreciate that the conception, upon which the disclosure is based, may be readily utilized as the basis for designing other structures, assemblies, method steps and system configurations for carrying out the objects of the present invention. It is important, therefore, that the broad outline of the invention described above be regarded as including such equivalent features insofar as they do not depart from the spirit and scope of the present invention.

BRIEF DESCRIPTION OF DRAWINGS

Fig. l is a perspective view of a combination of wood based formwork components used in the prior art for construction of stairs.

Fig. 2 is a perspective view of an assembly of the wood based formwork components shown in Fig. 1, the assembly being for use in forming a step of the stairs.

Fig. 3 is a perspective view of a wood based formwork assembly for forming stairs created from a plurality of the step forming assembly of Fig. 2, and into which concrete has been poured.

Fig. 4 is a side view of the wood based formwork assembly shown in Fig. 3, and the poured concrete therein.

Fig 5 is an isometric view of a formwork apparatus for the construction of stairs according to a first embodiment of the invention, the formwork apparatus being for use in forming a step of the stairs.

Fig. 6 is a front side view of the formwork apparatus of Fig. 5 showing the range of angular adjustment of the left and right end anchor plates. Fig. 7 is an exploded isometric view of the formwork apparatus of Fig. 5 showing its interconnectable components.

Fig. 8 is an enlarged sectional view through A-A of Fig. 6 showing the mating configuration of a bridging connector and the right side extender arm when tightly clamped together at a desired length of the formwork apparatus.

Fig. 9 is an enlarged view of an exploded right end of the formwork apparatus of Fig. 5 showing how a right end anchor plate can be connected to a right side extender arm.

Fig. 10 is an enlarged view of an exploded left end of the formwork apparatus of Fig. 5 showing how a left end anchor plate can be connected to a left side extender arm, and also showing how the left end anchor plate, when connected, can be angularly adjusted.

Fig. 11 is a top view of the formwork apparatus of Fig. 5 at its minimum retracted length.

Fig. 12 is a top view of the formwork apparatus of Fig. 5 at its maximum extended length.

Fig. 13 is a right end view of the formwork apparatus of Fig. 5 about to be secured to a conventional riser board which has been cut to a desired length and height. Fig. 14 is a side view of a formwork assembly for forming stairs created from a plurality of the formwork apparatus of Fig. 5, and into which concrete has been poured.

Fig. 15 is an isometric view of the formwork assembly shown in Fig. 14 and the poured concrete therein. BEST MODE OF CARRYING OUT THE INVENTION

The wood based formwork components of the prior art shown in Fig. 1 have all been cut to a desired size to suit the space into which the stairs are to be constructed. The formwork components consist of a riser board 12, a waler 14 (for distributing the load created by the poured concrete against the riser board), and a pair of riser cleats, namely, a left end riser cleat 16 and a right end riser cleat 18. Nails are used to secure the riser cleats 16, 18 to respective opposite ends of the waler 14, and also to secure the waler 14 against the riser board 12, thereby creating a wood based step forming assembly 20 as shown in Fig. 2. Figs. 3 and 4 show stairs 22 being constructed between two walls 24, 26. Individual step forming assemblies 20 are positioned tightly in the appropriate spaces between the walls 24,

26. The riser cleats 16, 18 may require some significant physical manipulation, such as with the use of a mallet or hammer, to ensure that their outer surfaces are properly fitted and are flush against the respective wall surface.

After installation of the wood based formwork assembly, concrete 28 is poured into the voids created by the formwork and the walls in the conventional manner. The concrete is allowed to cure to form the concrete steps 29, whereupon the formwork is removed, and much of the formwork will then go to waste.

The embodiment of the formwork apparatus 30 of the invention shown in Figs. 5 and 6 has a left side extender arm 32 and a right side extender arm 34, each of which are slidably connected to a bridging connector 36 which spans the extender arms 32, 34 so as to form an adjustable waler structure 35. The extender arms 32, 34 and the bridging connector 36 are, in this embodiment, made of metal.

The formwork apparatus 30, in a preferred form, also has a left end anchor plate 38 and a right end anchor plate 40 which are connected to opposite ends of the adjustable waler structure 35. The anchor plate 38 is adjustably connected to the left end of the left side extender arm 32, and the anchor plate 40 is adjustably connected to the right end of the right side extender arm 34. These formwork components 32, 34, 36, 38 and 40 are shown in exploded view in Fig. 7. The anchor plates 38, 40 are, in this embodiment, made of metal.

As shown in Figs. 7 and 8, the left and right side extender arms 32, 34 each have upper and lower flange portions 50, 52 with inner surfaces 54, 56 which are configured to engage and press against a riser board 57 cut to an appropriate length and height for each step (see also Fig. 13).

The left and right side extender arms 32, 34 also each have a central channel portion 58, 60 with male outer surfaces 62, 64 which are configured to mateably engage within, and be tightened (and loosened) against, female inner surfaces 66 of a main channel portion 68 of the bridging connector 36.

The left and right side extender arms 32, 34 can each individually slide relative to the bridging connector 36 via the engagement of the respective central channel portion 58, 60 of the extender arm with the main channel portion 68, thereby adjusting the length of the waler structure 35 of the formwork apparatus 10.

As shown in Figs. 6, 9 and 10, the anchor plates 38, 40 have mirror image structures comprising a flat main panel 90 and a connector bracket 92 secured to the inner side of the main panel 90. The main panel 90 has apertures 94 at predetermined locations that allow for direct securing by fasteners (such as screws) of the main panel 90 to a wall, stringer or other upright surface (i.e. either vertical or not vertical upright surfaces) at opposite sides of the stairs being constructed.

As best shown in Fig. 10, the connector bracket 92 has a top panel 96 and a side panel 98. The top panel 96 has an upper elongated slot 100 for receiving an upper bolt 102, and there is an upper threaded opening 104 for screwably engaging the upper bolt 102 at an outer end of a top part 82 of the central channel portion 58, 60 of each extender arm 32, 34. The side panel 98 has a lower elongated slot 106 for receiving a lower bolt 108, and there is also a lower threaded opening 110 for screwably engaging the lower bolt 108 at an outer end of the male outer surface 62, 64 of the central channel portion 58, 60 of each extender arm 32, 34.

The direction of elongation of the upper and lower slots 100, 106 allows for a perpendicular adjustment of the distance that the anchor plate 38, 40 can be moved away from the end of its respective extender arm 32, 34, and also allows for an angular (non-perpendicular) adjustment of the anchor plate 38, 40 to suit its engagement against upright surfaces which are not vertical at opposite sides of the stairs being constructed.

Such angular adjustment is facilitated by using the lower bolt 108 to provide a horizontal axis of rotation for the anchor plate 38, 40 and by rotating the anchor plate to the desired non vertical angle (up to about 15° to 20° from vertical as shown in Fig. 6), whereupon the upper bolt 102 is then received through the upper elongated slot 100 (of the now non-horizontal top panel 96) and is screwably engaged in the upper threaded opening 104 to maintain the angularly adjusted connection of the anchor plate 38, 40 with its extender arm 32, 34.

Figs. 11 and 12 show the minimum and maximum extents, respectively, of slidable movement of the extender arms 32, 34 relative to the bridging connector 36. From the minimum retracted length of the formwork apparatus 30 shown in Fig. 11, one or both of the extender arms 32, 34 can be slid away from the other for the formwork apparatus 30 to reach a desired length corresponding to the length of the riser board 57 it will engage and press against. However, the extender arms 32, 34 should not be slid away from each other any further than a maximum extended length (shown in Fig. 12). The maximum extended length is identifiable by stop holes 70, 72 (shown in Figs. 5 to 7) which are symmetrically located on either side of the middle of the bridging connector 36. The location of the stop holes 70, 72 is selected for maintaining a desired strength and support of the formwork apparatus 30, when extended, against the riser board 57.

When the length of the formwork apparatus 30 is adjusted to match the length of the riser board 57, screws 73 are used (see Fig. 13) to secure the formwork apparatus against the riser board. The screws 73 pass through holes formed at predetermined locations along the upper and lower flange portions 50, 52 of each extender arm 32, 34.

Strength and support of the formwork apparatus 30, when at its desired length, is also provided by the tight clamping together of the bridging connector 36 and the extender arms 32, 34. As shown in Fig. 8, the bridging connector 36 has an upper channel portion 74 connected to the main channel portion 68. Within the upper channel portion 74 are a series of spaced apart nuts 76, the top and bottom openings of each nut 76 being aligned with similarly sized openings in the top and bottom parts 78, 80 of the upper channel portion 74. The top part 82 of the central channel portion 60 of the extender arm 32, 34, over which slides the bottom part 80 of the upper channel portion 74 of the bridging connector 36, does not have any similarly sized openings. Each nut 76 is screwably engaged by a bolt 84 which passes through the openings in the top and bottom parts 78, 80 of the upper channel portion 74 of the bridging connector 36. However, the tip 86 of the bolt 84 (i.e. the leading end of the bolt’s threaded shaft) can only press down on the top part 82 of the central channel portion 60 of the extender arm 32, 34.

After the formwork apparatus is secured against the riser board 57, the bolts 84 are tightened and apply increasing force against the top part 82 of the central channel portion 60. This creates slight localized distortions of the central channel portion 60 and the main channel portion 68, which urges them together more tightly and causes the formwork apparatus 30 to apply more pressure against the riser board 57. This stabilizes the riser board 57 in readiness for the pour of concrete into the void behind the riser board.

Figs. 14 and 15 show an installed formwork assembly for forming stairs 112 created from a plurality of the formwork apparatus 30, and into which concrete 114 has been poured. In the process of constructing the concrete stairs 112, the bottom step 116 is formed first, followed by the forming of successive upper steps. Although Figs. 14 and 15 show the installation of formwork apparatus 30 for all of the steps, a single formwork apparatus 30 may instead be re used for forming the successive steps.

After use, the formwork apparatus 30 can be removed by disconnecting the anchor plates 38, 40 from the extender arms 32, 34, withdrawing the screws 73 from the riser board 57, and then pulling the remaining adjustable waler structure 35 from the riser board. The riser board 57 can then be removed from the formed step.

The metal that is used in the making of the main components of the formwork apparatus 30 is ideally selected from the group consisting of steel, mild steel, stainless steel, and aluminium, although any other suitable metal or metal alloy or composite material with the required strength and other structural and functional properties may be used.

As will be apparent from the above description of embodiments of the invention, the significant problem of waste associated with the use of conventional wood based formwork in the construction of concrete stairs is eliminated or at least substantially reduced. There is no longer any material wastage in the off cuts of wood and other wood based materials that are left over after pieces have been cut to a desired size and shape to create formwork in accordance with conventional processes for constructing concrete stairs.

It is another advantage of the present invention that it is no longer a labour intensive, time consuming and costly task to create formwork for constructing concrete stairs. Indeed, the length adjustable formwork apparatus of the present invention is quick and easy to use, and can be readily re-used.

It will be readily appreciated by persons skilled in this art, upon reading this description of embodiments of the invention, that there may be alternative embodiments of formwork apparatus for constructing concrete stairs which fall within the scope of the invention.

It will also be readily apparent to persons skilled in the art that various modifications may be made in details of the design and construction of the above embodiments of the formwork apparatus without departing from the scope or ambit of the present invention.

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 acknowledgement 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 before the filing date of this patent application.