Stairway manufacture

Abstract: A set of L-shaped modular step forming elements (10) are arranged within a mould (20) on support rails (21) to define a stairway of steps having a desired riser and tread. Each element (10) comprises a steel sheet bent intermediate its ends into an L-shape having a riser panel (11) and a tread panel (12). Spaced-apart stringer panels (23,24) which engage the elements (10) define a required stairway width and end panels extending between the stringer panels (23,24) close off each end of the mould (20) to define the length of the stairway. Steel reinforcement such as bars or a cage (28) is mounted on the step forming elements (10) and then concrete (29) is poured into the mould (20) covering the cage (28). A poker vibrator is inserted into the concrete (29) and vibrated to settle the concrete (29) and exclude air from the mould (20). A heating element (26) may be operated to accelerate the setting of the concrete (29) in the mould (20). After the concrete is set the stairway thus formed is removed from the mould.

Description: This invention relates to the manufacture of precast concrete stairways. In one method of manufacturing precast concrete stairways a wooden mould is prepared typically comprising a base shaped in the desired stair configuration with upstanding side and end panels to retain concrete poured into the mould. A reinforcement cage is mounted on the base and the concrete is poured into the mould covering the cage. A poker vibrator may be inserted into the concrete to settle the concrete within the mould and exclude air. One problem with wooden moulds is the time taken to construct them for which a skilled mould maker is required. Each mould is of a specific size for a particular application. Also they have a relatively short useful life and can be used only for a very limited number of castings as the surface of the mould tends to deteriorate rapidly which adversely affects the quality of the stairway produced. Also the mould may be damaged by the poker vibrator if it is used to settle the concrete in a mould and engages a mould face upon insertion into the concrete. Wood being a good insulator it is not practical to heat the mould to accelerate the setting of the concrete and therefore the casting time is relatively long. If the mould is not being discarded then the size of the mould presents a storage problem. Patent Specification US 5511347 discloses a shaped riser pan, a number of which are assembled on site and welded together in situ to form a stairway. A ladle portion of each pan is then filled with concrete to form a tread for each step. Modified pans can also be used to form portion of a mould for precast concrete stairways. A plurality of the pans are interconnected end to end by adjustable clamps to form an integral stairway former in the bottom of a mould in which concrete is cast to form a stairway. JP 02265705 discloses mounting a plurality of L-shaped wooden elements on a pair of steel outer frame to form a mould for casting a stairway. FR 2546440 comprising the features of the preamble of claim 1, shows a wooden mould for forming a precast concrete stairway. DE 19546050 relates to shuttering for forming a precast concrete stairway which includes a support frame on which step moulds are height and tilt adjustable. It is also known to provide an adjustable stairway moulding apparatus which essentially moulds a concrete stairway on its side. Examples of such moulding apparatus are given in Patent Specification Nos. GB2217359, GB2193922 and DE3518200. A disadvantage associated with this moulding apparatus is the fact that it is of relatively complex and expensive construction. Typically, a single stairway can be manufactured in each mould per day. Therefore if it is desired to produced a large number of stairways, either a very long construction time is required using a single moulding apparatus, or if it is desired to reduce production time by moulding a number of stairways each day several moulds are required resulting in considerable expense to the manufacturer. Also, because the stairways are moulded on their side, access to the mould is restricted requiring considerable height clearance above the mould for pouring concrete into the mould and for lifting the formed stairway out of the mould. Further, a relatively narrow inlet is provided for filling the mould with concrete when an edge moulding method is employed. The present invention is directed towards overcoming these problems. According to the invention there is provided apparatus for manufacturing a precast concrete stairway comprising the features of claim 1. In another embodiment each modular step forming element comprises an L-shaped inwardly facing moulding wall having a riser forming face and a tread forming face. Preferably the internal angle between the panels is an acute angle. Ideally the element is formed by a sheet of metal bent intermediate its ends. In a further embodiment the step forming elements are interengagable. Preferably the retaining flange extends along the free edge of the tread panel. In another embodiment the mould comprises a flat support on which the set of step forming elements is arranged between end panels which define the length of the stairway and a pair of spaced-apart side stringer panels extend outwardly of the step forming elements between the end panels to define the width of the stairway. In another embodiment the step forming elements are clamped between a pair of spaced-apart fixed stringer panels and an adjustable stringer panel is provided for optionally mounting between the fixed stringer panels for width adjustment of the stairway. In a further embodiment each step forming element has reinforcing means mounted between the panels. Preferably the reinforcing means is one or more stiffening webs mounted between the panels. Conveniently the webs may be provided with a notch therein shaped for reception of the joined edges of the panels of the step forming element to facilitate stacking of the step forming elements when not in use. In another aspect the invention provides a step forming element and a set of step forming elements as described herein for use in the apparatus. In a further aspect the invention provides a method for manufacturing a precast concrete stairway using the apparatus comprising: preparing a mould incorporating a plurality of the step forming elements; preparing liquid concrete; pouring the liquid concrete into the mould: setting the liquid concrete to form a stairway; and removing the stairway from the mould. In a preferred embodiment the method includes mounting reinforcement means in the mould prior to pouring the liquid concrete into the mould. Preferably the reinforcement means is a reinforcing cage. In a particularly preferred embodiment the method includes the step of vibrating the liquid concrete in the mould for settling the liquid in the mould prior to setting the concrete in the mould. In another embodiment the method includes the step of heating the mould for accelerating the drying of the concrete in the mould. The invention will be more clearly understood by the following description of some embodiments thereof, given be way of example only, with reference to the accompanying drawings, in which: Fig. is a perspective view of a modular step forming element according to the invention; Fig. 2 is an end view of the step forming element; Fig. 3 is a perspective view of a set of modular step forming elements according to the invention Fig. 4 is a perspective view showing a pair of interengaging step forming elements with an associated spacer therebetween; Fig. 5 is a detail exploded partially sectioned elevational view of a mould apparatus for moulding a precast concrete stairway using the step forming elements; Fig. 6 is a sectional end view of the mould; Fig. 7 is an end elevational view of another step forming element; Fig. 8 is a sectional view taken along the line VIII-VIII of Fig. 7; Fig. 9 is a partially sectioned elevational view of a mould apparatus for moulding a pre-cast concrete stairway using the step forming elements of Fig. 7; Fig. 10 is a sectional end view of the mould apparatus; Fig. 11 is a detail end elevational view of an end plate forming portion of the mould apparatus; Fig. 12 is a detail end elevational view of another end plate forming portion of the mould apparatus of Fig. 9; Fig. 13 is an elevational view of the end plate shown in Fig. 12; Fig. 14 is an end elevational view of the end plate of Fig. 13; Fig. 15 is an elevational view of a stair mountingbracket; Fig. 16 is a view similar to Fig. 13 of the end plate shown in Fig. 11; Fig. 17 is an end elevational view of the end plate of Fig. 16; Fig. 18 is an elevational view of a stair mounting bracket; Fig. 19 is a sectional elevational view of a stairway produced using the mould apparatus of Fig. 9 and incorporating the stair mounting brackets of Figs. 15 and 18; Fig. 20 is a view similar to Fig. 9 showing another mould apparatus; Fig. 21 is an elevational view of an end plate forming portion of the mould apparatus of Fig. 20; and Fig. 22 is an elevational view of another end plate for the mould apparatus of Fig. 20. Referring to the drawings, there is illustrated apparatus for manufacturing a precast concrete stairway comprising a set of modular step forming elements 10 which can be arranged side by side in a row, as illustrated in Figs. 3 and 5, within a mould to define a stairway of steps having a desired riser and tread. Each step forming element 10 comprises a steel sheet bent intermediate its ends into an L-shape having a riser panel 11 and a tread panel 12. The included angle A between the panels 11,12 is an acute angle. A retaining flange 14 is provided along a free edge of the tread panel 12 and serves to interengage the panels 10 when they are arranged in a row as shown in Fig. 3 to form a stairway mould face. As can be seen the riser panel 11 of one step forming element 10 is engagable with the tread panel 12 of the adjacent step forming element 10. Thus a stairway with any desired number of steps can be built up in a mould 20 as shown in Fig. 5. It will be noted that to adjust the going X a spacer 16 may be mounted between the retaining flange 14 of one step forming element 10 and a back face of the riser panel 11 of the adjacent step forming element 10. Thus conveniently the going can be readily easily adjusted to accommodate different desired stairway constructions. To accommodate different riser variations twenty sets of the step forming elements 10 can be provided each set having riser panels 11 of different depth. This will provide a riser variation of between 150mm and 190mm at 2mm intervals. Conveniently for storage the step forming elements 10 will nest together. To differentiate between the twenty different types of step forming elements 10 they can conveniently be colour coded or marked in any other suitable fashion. It may be desirable in some circumstances to provide a strengthening web, gusset or the like between the riser panel 11 and tread panel 12. Referring to Figs. 5 and 6 a mould 20 incorporating the step forming element 10 is shown. In this case the mould 20 comprises a flat support formed by a pair of spaced-apart rails 21 which have substantially horizontal upper support surfaces. A set of the step forming elements 10 are mounted on the rails 21 as shown in Fig. 5 extending outwardly from a fixed stringer panel 23 at one side of the mould 20. A movable stringer panel 24 is positioned on the step forming elements 10 a desired distance apart from the fixed stringer panel 23 to give a desired stair width. End plates (not shown) dose off each end of the mould 20. A heating element 26 is mounted between the rails 21 and is operable to heat the mould 20 for accelerated curing of the concrete. In use, a set of the step forming elements 10 are arranged in the mould 20 as shown in Fig. 5 with the desired riser and going dimensions. A steel reinforcement cage 28 is mounted on the step forming elements 10 and then concrete 29 is poured into the mould 20 covering the cage 28. A poker vibrator is then inserted into the concrete 29 to vibrate the concrete 29 for settling the concrete 29 in the mould 20 and exclude air from the concrete 29. The heating element 26 may be operated to heat the mould 20 with a view to accelerating the setting time of the concrete 29 thus advantageously reducing the production time. When the concrete 29 has set the stairway thus produced is lifted from the mould for delivery to storage or to a desired site. Referring now to Figs. 7 to 19 there is illustrated another apparatus for manufacturing a pre-cast concrete stairway comprising a set of modular step forming elements 30 which are largely similar to the step forming elements described previously. Each step forming element 30 comprises a steel sheet bent intermediate its ends into an L-shape having a riser panel 31 and tread panel 32. A retaining flange 34 is provided along a free edge of the tread panel 32 and serves for interengagement of the panels 30 when they are arranged in a row as shown in Fig. 9 to form a stairway mould face. The riser panel 31 of one step forming element 30 is engagable with the tread panel 32 of the adjacent step forming element 30. Thus a stairway with any desired number of steps can be built up in a mould 40 as shown in Fig. 9. As previously described, to adjust the going of each step a spacer 36 can be mounted between the retaining flange 34 of one step forming element 30 and a back face of the riser panel 31 of the adjacent step forming element 30. Thus conveniently the going can be readily easily adjusted to accommodate different desired stairway configurations. In this case reinforcement is provided between the panels 31, 32 in the form of four spaced-apart stiffening webs 38. This conveniently allows relatively thin material to be used for the panels 31, 32, to facilitate ease of handling, whilst at the same time maintaining adequate strength to prevent spreading of the panels 31, 32 when the concrete is poured into the mould 40. It will be noted that a notch 39 is provided at a bottom of each web 38, this notch 39 having the same shape as the angle of the panels 31, 32 so that the common edge 40 of the panels 31, 32 nests within the notch 39 for convenient stacking of the elements 30 when not in use. Figs. 9 and 10 show the mould 40. A set of the step forming elements 30 are mounted on three spaced-apart support rails 42. Outer, fixed stringer panels 43 engage the sides of the elements 30 which are clamped between the outer stringer panels 43 by means of clamp bars 44 with lock nuts 45, the clamp bars 44 extending between the stringer panels 43. An adjustable stringer 46 can be mounted between the fixed stringers 43 to adjust the width of a stairway being produced. The adjustable stringer 46 can be mounted to one of the side stringers 43 in any suitable fashion. Ends of the mould 40 are dosed off by end plates 48, 49 mounted between the fixed side stringers 43 by supports 50. It will be noted that each of the end plates 48, 49 is of stepped construction. This advantageously reinforces the end plates 48, 49 allowing use of lighter material to facilitate handling and also forms a recess 52 at each end of the stairway 53 produced for reception of mounting brackets 55 which are secured by bolts 56 within the recess 52 such that the bolts 56 do not project outwardly of the recess 52. The mounting brackets 55 are of L-section and are for engagement with upper and lower landings in a building. The mounting bracket 55 is not required at a lower end of the stairway when the stairway is the bottom stairway of the building. Referring to Figs. 13 to 16 the end plates 48, 49 are shown in more detail. Each end plate 48, 49 has a plurality of spaced-apart openings or through holes 60. This is to allow through passage of mounting bolts for supporting a threaded anchor socket within the end of each mould said anchor sockets being for reception of the bolts 56 which hold on the mounting brackets 55. Any of the holes 60 not being used are simply plugged before the casting process. A bar 61 is provided on an outside of the end plate 48, 49 and bolts passing through holes 62 in the bar 61 engage and clamp the anchors against the inner face of the end plates 48, 49 for positioning the anchors within the mould prior to casting. Fig. 19 shows a stairway 53 produced using the mould, the stairway 53 having a plurality of steps 70 each having a tread 71 and a riser 72. It will be appreciated that the mould according to the invention is easy and simple to set up and use. Also good access is provided for pouring concrete into the mould and for extracting the moulded stairway from the mould. Lifting lugs (not shown) are integrally moulded with the stairway 53 to facilitate lifting the stairway out of the mould, the lifting lugs being provided at a soffit face 75 of the stairway 53. Figs. 20 to 22 show another mould configuration with a different end plate 80 arrangement. It will be appreciated that the invention provides an apparatus and method for manufacturing a precast concrete stairway in a simple and efficient manner. It will be appreciated that the moulding apparatus is readily easily adjustable to accommodate different stairway dimensions. It is easy to prepare a stairway mould of any desired length by adding or removing step forming elements. Also, the width of stairway produced is easily adjusted by a movement of the stringer panels together or apart as required to select a desired stairway width. Further, the dimensions of the going and the riser can also be simply adjusted as described herein. It will be noted also that steel, from which the step forming elements are formed, is a much better heat conductor and allows quicker heat curing of the concrete in the mould than can be achieved with wooden moulds. Furthermore the steel construction is more robust than wooden moulds and less susceptible to damage. It will also be appreciated that one or both ends of the mould may be shaped to form a landing at one or both ends of the stairway.

Claims: Apparatus for manufacturing a precast concrete stairway comprising a mould (20) having an internal step-forming face for shaping a desired stairway configuration in concrete delivered into the mould (20), the step forming face comprising a set of individual modular step forming elements (10) mounted side by side in the mould (20) to define a stairway of steps having a desired tread and riser, each step forming element (10) being shaped having a riser panel (11) and a tread panel (12), a retaining flange (14) is provided along a free edge of a panel (11, 12) for engagement with a free edge of another step forming element (10), characterised in that wherein the set of modular step forming elements is adjustable to adjust the going of the tread, wherein a spacer (16) is provided associated with each step forming element (10) for mounting between the retaining flange (14) of the step forming element (10) and the riser panel (11) of an adjacent step forming element (10) for adjustment of the going of the tread panel (12). Apparatus as claimed in claim 1, wherein each modular step forming element (10) comprises an L-shaped inwardly facing moulding wall having a riser forming face and a tread forming face. Apparatus as claimed in any preceding claim, wherein the internal angle between (10) the panels is an acute angle Apparatus as claimed in any preceding claim, wherein the step forming elements are interengagable. Apparatus as claimed in claim 1, wherein the retaining flange (14) extends along the free edge of the tread panel (12). Apparatus as claimed in any preceding claim, wherein the mould (20) comprises a flat support (21) on which the set of step forming elements (10) is arranged between end plates which define the length of the stairway and a pair of spaced-apart side stringer panels (23, 24) extend outwardly of the step forming elements (10) between the end plates to define the width of the stairway. Apparatus as claimed in any preceding claim wherein the step forming elements (10) are clamped between a pair of spaced-apart fixed stringer panels (23) and an adjustable stringer panel (24) is provided for optionally mounting between the fixed stringer panels (23) for width adjustment of the stairway. Apparatus as claimed in any preceding claim wherein each step forming element (30) has reinforcing means (30) mounted between the panels (31, 32). A method for manufacturing a precast concrete stairway using the apparatus as claimed in any preceding claim comprising: preparing a mould (20) incorporating a plurality of the L-shaped step forming elements (10) being adjustable to adjust the going of the tread by mounting spacers (16) between the adjacent flanges (14) of the step forming elements (10) and the riser panels (11) of adjacent step forming elements (10); preparing liquid concrete; pouring the liquid concrete into the mould(20); : setting the liquid concrete to form a stairway; and removing the stairway from the mould (20). A method as claimed in claim 9, wherein the method includes mounting reinforcement means (28) in the mould (20) prior to pouring the liquid concrete into the mould (20). A method as claimed. in claim 10, wherein the reinforcement means is a reinforcing cage (28). A method as claimed in any of claims 9 to 11 wherein the method includes the step of vibrating the liquid concrete in the mould(20) for settling the liquid in the mould (20) prior to setting the concrete in the mould (20). A method as claimed in any of claims 9 to 12, wherein the method includes the step of heating the mould(20) for accelerating the drying of the concrete in the mould (20).

Inventors: GERAGHTY KEVIN, GERAGHTY, KEVIN
Applicants: GERAGHTY KEVIN, GERAGHTY, KEVIN
Application year: 1999
Main classification: B28B7
IPC codes: B28B7