CA2920585A1 - Modular framework for a curved or grand staircase - Google Patents

Abstract

A modular staircase framework features a plurality of steps. Each step comprises a pair of stringer plates and a tread plate. First and second stringer plates are arranged to be laterally opposite one another, and the tread plate is arranged to span between the stringer plates. Furthermore, the first stringer plates are arranged to collectively define a first stringer and the second stringer plates of the steps are arranged to collectively define a second stringer. Within each pair of steps arranged to be adjacent one another, each stringer plate of a first step comprises holes along a first edge thereof, and each stringer plate of a second step comprises tabs projecting from a second edge thereof for coupling to the holes of the stringer plates of the first step. The stringer plates and the tread plate are fabricated from flat sheet metal using a cutting method controlled by a computer.

Description

MODULAR FRAMEWORK FOR A CURVED OR GRAND STAIRCASE
This application claims the benefit of US Provisional Application 62/114,664 filed February 11,2015.
FIELD OF THE INVENTION
The present invention relates generally to a modular framework for a staircase, and more particularly the present invention relatives to a modular framework for a curved staircase that comprises a plurality of plates cut from sheet metal.
BACKGROUND
The unique designs, especially the curvature, of curved staircases and grand staircases makes them aesthetically pleasing. While curved staircase comprise inner and outer stringers which have constant curvature generally in one direction, grand staircases may comprise at least one stringer which is curved more than once in two different directions (i.e., the stringer has a convex portion and a concave portion to its shape in plan view). As such, a curved or grand staircase may add considerable value to a building. However, knowledge and craftsmanship required to build this type of staircase means that a cost of the curved or grand staircase is significant compared to rectilinear staircases which are simpler in design. In fact, building curved and grand staircases is often regarded as an art form because of the complexity in fabricating and assembling pieces of the staircase. As such, it is likely that building owners may be dissuaded from installing more aesthetically pleasing staircase designs such as those of the curved or grand staircase type based on the sheer cost often associated with these staircases.
Fabrication and assembly of staircases in sections, especially of a

2 framework of the staircases, has been known in the art of staircase building for some time. It serves as one way of reducing the costs associated with installing staircases by fabricating parts of a modularized framework and assembling the parts thereof on-site. For example, U.S. Patent No. 4,422,270 to Lapointe teaches a modular, self-supporting staircase. The staircase is made up of sections. Each section includes two vertical side plates and a tread supported across the side plates. The side plates have vertical flanges which overlap a portion of an adjacent side plate that is part of an adjacent step of the staircase. The vertical side plates also have an upper flange which is L-shaped in plan view that supports the tread thereon. While the patent to Lapointe may solve the problem of providing inexpensive metal framework in sections, one potential shortcoming of the patent to Lapointe may be difficulty to adapt to the curved staircase.
Another example of modularized staircase design is German Patent Application 102011015492 to Uhlenbusch. The patent to Uhlenbusch describes stringer sections which are made from sheet metal. Each stringer section has vertical flanges that are perpendicular to a main portion of the plate that is substantially planar. The vertical flanges of pairs of adjacent plates overlap for coupling the sections together. One of the potential shortcomings of the patent to Uhlenbusch may be difficulty to adapt to the curved or grand staircase.
The Applicant provides a unique solution for curved or grand staircases that may be less expensive to manufacture; easier to assemble on-site at the building;
and which may make curved staircases and grand staircases more accessible to those individuals who may not be able to afford installation of traditional curved or grand staircases.

3 SUMMARY OF THE INVENTION
According to one aspect of the invention there is provided a modular staircase framework for assembly in sections comprising:
a plurality of steps, each step comprising:
a first stringer plate;
a second stringer plate laterally opposite the first stringer plate;
the first and second stringer plates being oriented substantially upright and substantially parallel to one another;
the first and second stringer plates having opposing first and second upright edges; and a tread plate spanning between the first and second stringer plates in a horizontal orientation;
the first stringer plates of the steps collectively defining a first stringer and the second stringer plates of the steps collectively defining a second stringer;
within each pair of adjacent steps, the stringer plates of each respective stringer being aligned so that the first upright edge of the stringer plate of one step is adjacent the second upright edge of the stringer plate of another step;
within at least one pair of adjacent steps:
at least one of the first or second stringer plates of a first step comprising a receiving element at or adjacent the first upright edge thereof;
and at least one of the first or second stringer plates of a second step comprising a coupling element at or adjacent the second upright edge thereof for coupling to the receiving element of an adjacent one of the stringer plates of the first step;
wherein the first and second stringer plates and the tread plate are

4 fabricated from sheet metal using a cutting method controlled by a computer.
The embodiment of the invention as described in more detail hereinafter provides a modular staircase framework which can be assembled in sections and which can be inexpensively manufactured (in mass quantities) by cutting components of the framework out of sheet metal. The components, typically which are substantially flat, may be more easily packaged and shipped across large distances including international shipping. Using the computer-controlled cutting method affords feasible fabrication of parts for curved staircases in which a majority of the parts may have unique dimensions. In a situation where a plurality of parts have dimensions which are unique to a few of the parts, fabricating the plurality of parts by casting or using molds is not as practical as using a computerized cutting tool which is configured to accommodate differences from part to part. Furthermore, a staircase design can be easily adjusted to fit a height between levels by adjusting corresponding plate dimensions. Also, a plurality of shapes may be accommodated by the computerized cutting tool. In addition, the computer controlled aspect of the cutting method affords precision in meeting building codes for staircases.
Design work for the modular staircase framework, which may be done in computer programs including AutoCAD, allows the design to be exported into programs like SolidWorks for load testing simulations and other simulated structural assessments. In general, the embodiment of the invention affords centuries of staircase building knowledge to be incorporated and preserved using modern technology including the computer and software programs such as AutoCAD.
In one instance, the cutting method comprises laser cutting. In another instance, the cutting method comprises plasma cutting.
Preferably, the coupling element is overlapping the receiving element along a planar surface of the at least one of the first or second stringer plates of the first step.
Preferably, the receiving element comprises at least one hole. When the receiving element comprises the at least one hole, it is preferred that said at least one

5 hole comprises a plurality of holes along the first upright edge.
Preferably, the coupling element comprises at least one tab projecting from the second upright edge of said at least one of the first or second stringer plates of the second step, said at least one tab being arranged for overlapping the receiving element. When the coupling element comprises the at least one tab, it is preferred that said at least one tab comprises a plurality of tabs along the second upright edge.
Preferably, the coupling element is bent at an angle from a planar surface of said at least one of the first or second stringer plates of the second step for introducing a curve in the staircase.
Preferably, the coupling element is integral with said at least one of the first or second stringer plates of the second step.
Preferably, each one of the first and second stringer plates comprises a top edge spanning between the first and second upright edges thereof, and at least one of the first or second stringer plates includes a tread mounting element at or adjacent the top edge thereof. In one instance, the tread mounting element comprises at least one flange along the top edge that is arranged for coupling the tread plate thereto. When the tread mounting element comprises the at least one flange, the at least one flange is optionally a plurality of flanges along the top edge. In another instance, the tread mounting element comprises at least one projecting element projecting from the top edge that is arranged for riveting the tread plate.
When the tread mounting element comprises the at least one projecting element, it is preferable

6 that the at least one projecting element comprises a plurality of projecting elements along the top edge.
Preferably, the first stringer plate has a first plate width measured between the first and second upright edges thereof and the second stringer plate has a second plate width measured between the first and second upright edges thereof, and when the first and second stringers are curved for creating a curved staircase, the first plate width of at least one of the first stringer plates is different from the first plate width of at least another one of the first stringer plates and the second plate width of at least one of the second stringer plates is different from the second plate width of at least another one of the second stringer plates.
Preferably, at least one of the steps further comprises a riser plate spanning between the first and second stringer plates thereof, the riser plate being arranged in an upright orientation between the first and second stringer plates. Each tread plate comprises opposing inner and outer edges spanning between laterally opposing side edges of the tread plate, the inner edge being arranged closer to the second upright edges of the first and second stringer plates of each step than to the first upright edges thereof and the outer edge being arranged closer to the first upright edges of the first and second stringer plates of each step than to the second upright edges thereof. The riser plate comprises opposing top and bottom edges spanning between laterally opposing upright side edges, the top and bottom edges and the upright side edges collectively defining an outer periphery of the riser plate.
Preferably, the riser plate further comprises a plurality of projecting elements along the outer periphery that are arranged for riveting to at least one of the tread plates or to the first and second stringer plates of said at least one of the steps. It is preferred that the projecting elements along the outer periphery comprises projecting elements

7 along the top edge of the riser plate for riveting to said at least one of the tread plates, and said at least one of the tread plates further comprises a plurality of holes along the outer edge arranged to receive the projecting elements of the riser plate therein. It is also preferred that at least one of the tread plates further comprises a plurality of projecting elements along the inner or outer edge that are arranged for riveting to the riser plate. Preferably, the projecting elements along the inner or outer edge of the tread plate comprise projecting elements along the inner edge thereof.
According to a second aspect of the invention there is provided a modular staircase framework kit for assembly in sections comprising:
a plurality of first stringer plates;
a plurality of second stringer plates arranged to be laterally opposite the first stringer plates;
wherein the first and second stringer plates have opposing first and second edges;
wherein the first and second stringer plates are arranged to be substantially upright and substantially parallel to one another;
a plurality of tread plates arranged to span between the first and second stringer plates in a horizontal orientation;
wherein the first stringer plates are arranged to collectively define a first stringer and the second stringer plates of the steps are arranged to collectively define a second stringer;
at least one of the first or second stringer plates comprising holes along the first edge thereof;
at least another one of the first or second stringer plates comprising tabs projecting from the second upright edge thereof for coupling to the holes of said at

8 least one of the first or second stringer plates;
wherein the first and second stringer plates and the tread plates are fabricated from sheet metal using a cutting method controlled by a computer.
Preferably, the first and second stringer plates and the tread plates are arranged to accept and incorporate thereon finishing materials including wood, cork, marble, glass, granite, and laminate that can sized and shaped using the first and second stringer plates and the tread plates as templates therefor. The finishing material may be sized and shaped using a cutting method comprising one of manual cutting, e.g., using a hand tool like a router, and computer controlled cutting.
Optionally, the first and second stringer plates comprise ornate designs therein that are cut out from the plates using the cutting method. The framework may be used in internal or external applications.
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred embodiments of the invention will now be described in conjunction with the accompanying drawings in which:
Figure 1 is a schematic illustration in top plan view of a grand staircase assembled from the modular staircase framework.
Figure 2 is an exploded view of a three adjacent steps of the modular staircase framework.
Figure 3 is an exploded view of a first two of the three adjacent steps in Figure 2 showing two embodiments of the tread mounting element of the stringer plates.
Figure 4A is a side elevation view of the stringer plates of two adjacent steps having first edge lengths `X1' and second edge lengths 'Y'.

9 Figure 4B is a side elevation view of the stringer plates of two adjacent steps, as in Figure 4A, having first edge lengths `X2' and second edge lengths 'V' where X2 > X1.
Figure 5 is a schematic illustration in top plan view of a series of assembled steps of the staircase framework, including a topmost step, with some components omitted for clarity of illustration.
Figure 6 is a schematic illustration in front elevation view of a series of assembled steps of the staircase framework, including the topmost step, with some components omitted for clarity of illustration.
Figure 7 is a schematic illustration in side elevation view of a series of assembled steps with some components omitted for clarity of illustration.
Figure 8 is an exploded view of another two adjacent steps more clearly illustrating coupling between tread plates and riser plates.
Figure 9 is a side elevation view of an embodiment of the modular staircase framework having extension plates.
In the drawings like characters of reference indicate corresponding parts in the different figures.
DETAILED DESCRIPTION
Referring to the accompanying figures, there is illustrated a modular staircase framework generally indicated by reference numeral 10 that is assembled in sections, generally one step of the staircase framework at a time. The modular staircase framework is especially suited for curved staircases or grand staircases.
Curved staircases generally comprise stringers which have constant curvature;
that is, for a generally longitudinal staircase which curves, a first stringer thereof is concave while an opposing second stringer is convex so that both stringers comprise curvature in one lateral direction. In contrast, grand staircases comprise at least one stringer, generally an outer one of the stringers, which comprises curvature in more than one lateral direction so that the outer one of the stringers has convex and concave 5 portions (more clearly seen in FIG. 1). Note that the modular staircase framework 10 may also be used for rectilinear staircases.
The modular staircase framework spans between an upper level U and a lower level L. A vertical height between upper and lower levels may vary.
The modular staircase framework has an upper end at a topmost step 12 of the staircase

10 framework and a lower end at a bottommost step 14 of the staircase framework.
The framework comprises a plurality of steps 16. The number of steps depends on two primary factors: (i) the vertical height between upper and lower levels; and (ii) a predetermined range for vertical spacing between treads of adjacent steps that is allowed by building code.
Each step has a pair of stringer plates 18. The pair of stringer plates comprises a first stringer plate 18A and a second stringer plate 18B which is laterally opposite the first stringer plate and spaced therefrom. The stringer plates of each step are oriented substantially upright and are substantially parallel to one another. When coupled together, the stringer plates collectively define respective stringers. More specifically, the first stringer plates of the steps collectively define a first stringer 20A
which for purposes of this description defines an inner radius of the curved staircase.
Similarly, the second stringer plates of the steps collectively define a second stringer 20B, and for the purposes of this description the second stringer defines an outer radius of the curved staircase. Aside from placement within the framework, general shape of the first and second stringer plates is substantially similar and consequently

11 discussed simultaneously below by reference to each stringer plate.
Generally speaking, each stringer plate 18 is substantially planar. Each stringer plate has opposing first 22 and second 24 edges. A top edge 26 of each stringer plate spans between the first and second edges at top ends thereof.
The top edge meets each one of the first and second edges at right angles such that the first and second edges are substantially parallel to one another. A bottom edge 28 is opposite the top edge. The bottom edge spans between bottom ends of the first and second edges and is curved as an aesthetic feature of the stringer plates. The first edge is longer than the second edge such that the bottom edge extends generally downwardly and forwardly from the second edge to the first edge when the stringer plates are oriented substantially upright. Furthermore, within each pair of adjacent steps, the stringer plates of each respective stringer are aligned so that the first edge of the stringer plate of a first step is adjacent the second edge of the stringer plate of an adjacent step which is generally lower than the first step. As such, the first edge is longer than the second edge in order to accommodate coupling of the stringer plate of the first step to the stringer plate of the adjacent step. Also, lengths of all first edges of the stringer plates are substantially the same and lengths of all second edges of the stringer plates are substantially the same so as to maintain consistent vertical spacing between the treads of adjacent steps. When the stringer plates are coupled in the respective stringers, the bottom edges of adjacent stringer plates are substantially flush so as to comprise a smooth, continuous, wavy contour along a bottom edge of the stringer.
Each stringer plate also has a plate width 'W' measured between the first and second edges, more clearly shown in FIG. 2. Depending on location of the particular stringer plate within the framework, the plate width of each stringer plate

12 may be different in order to properly form the curve of the staircase.
However, generally when considering each respective stringer the plate width of at least one stringer plate is different from the plate width of at least another one of the stringer plates in the framework for the curved staircase. For example, as more clearly shown in FIG. 5, the stringer plates of adjacent steps may have different widths W1 and W2 where W2 > W1 in order to achieve the proper curvature of the staircase.
Within each pair of adjacent steps, each stringer plate of the first step comprises a plurality of holes 30 spaced along the first edge thereof. The holes collectively define a receiving element of the stringer plate.
Further to the receiving elements of the first step, each stringer plate of a second step, which defines the adjacent step of the pair of adjacent steps, comprises a plurality of tabs 32 projecting from the second edge of each stringer plate. The tabs collectively define a coupling element of the stringer plate.
Furthermore, the tabs are integral with the stringer plate. Each one of the tabs has an outer periphery which is convex. Each one of the tabs has a hole therein that is aligned with a corresponding one of the holes in the stringer plate of the first step in an overlapping configuration. More specifically, the tabs of the stringer plate of the second step overlap a part of an outer planar surface of the stringer plate of the first step. Since the stringer plate of the first step may be angled away from the stringer plate of the second step, the tabs may be bent relative to the stringer plate of the second step at an angle away from a plane of the stringer plate for properly forming the curve when coupling adjacent stringer plates, as more clearly shown in FIG. 5 where the coupling element 32 is parallel to the plane of the immediately previous step at its receiving element 30 (which is typically coplanar with a main portion of the stringer plate). As such, each stringer plate is substantially rigid so that it can bear

13 weight of a load thereon; furthermore, each stringer plate which has tabs is substantially flexible at the tabs so that the tabs may be bent as described.
It is important to note that a majority of the stringer plates (i.e., both the first and second stringer plates) comprise both the receiving element and the coupling element because the majority of the stringer plates belong to two pairs of adjacent steps. In contrast, the stringer plates which form part of the topmost step 12 may only have the receiving elements for coupling to the adjacent step; in place of the coupling elements along the second edge 24, the stringer plates forming the topmost step may have another coupling element at or adjacent the second edges of the stringer plates for coupling to a structural member, such as a joist J, of the upper level U.
In the illustrated embodiment, the another coupling element of the topmost step comprises a joist coupling element 34 which is a planar flange with the tabs, like those which define the coupling element of remaining ones of the stringer plates, projecting therefrom in the plane of the flange. The flange is an extension of the second edge of the stringer plates of the topmost step and consequently spans a full length of the second edge. The joist coupling element is bent relative to the stringer plate, as the tabs of the remaining ones of the stringer plates, though at an angle away from the plane of the stringer plate that is generally greater than the angle between the tabs and the plane of one of the remaining stringer plates. Similarly to the topmost step, the stringer plates forming part of the bottommost step 14 may only have the coupling elements for coupling to the step adjacent the bottommost step; in place of the receiving elements, the stringer plates forming the bottommost step may have a fastening element at or adjacent the first edges of the stringer plates for coupling to the lower level.
Further to the stringer plates, each step of the modular staircase

14 framework also comprises a tread plate 36. The tread plate spans between opposing stringer plates of each step. The tread plate is oriented substantially horizontally. The tread plate is positioned on top of the stringer plates so as to lie flush along the top edges 26 thereof. Side edges 38 of the tread plate extend outwardly beyond the stringer plates in the illustrated embodiment.
Each tread plate is substantially planar. Each tread plate has an inner edge 40 which spans between the side edges of the tread plate. The inner edge is generally over the second edges 24 of the stringer plates of a respective step. An outer edge 42 of the tread plate is opposite the inner edge thereof so as to be generally over the first edges 22 of the stringer plates of the respective step. The inner edge may be arced inwardly, in a direction generally towards the outer edge so as to be concave relative to the side edges of the tread plate, and the outer edges may be arced outwardly, in a direction generally away from the inner edge so as to be convex relative to the side edges. In the illustrated embodiment, the outer edge of the tread plate extends outwardly beyond the first edges of the stringer plates so as to be over the tread plate of the adjacent step. Additionally, the side edges of each tread plate may have different lengths as the inner and outer radii of the curved staircase are different.
Turning back now to the stringer plates, each stringer plate has a tread mounting element at the top edge for mounting the tread plate thereto. In the illustrated embodiment, the tread mounting element comprises a plurality of rivets 44 projecting from the top edge at spaced locations along the top edge. The rivets define a projecting element. As the stringer plates may have different plate widths, spacing between the rivets of each stringer plate may vary from plate to plate;
however, spacing of each one of the rivets inwardly from an end of the top edge is substantially equal for the stringer plates. Further to the rivets on the stringer plates, the tread plates have holes 46 spaced inwardly from the side edges thereof which are aligned with the rivets of the stringer plates for accepting the rivets therethough.
To accommodate the vertical spacing between tread plates of adjacent 5 steps that may vary between implementations of the modular staircase framework, generally a first edge length 'X' of the first edge 22 of each stringer plate is adjusted.
The first edge length is measured along the first edge between the top 26 and bottom edges 28. As more clearly shown in FIG. 4, the first edge length is increased from 'X,' to `X2' (Le., X2 > X1) when the vertical spacing is larger, and conversely the first edge 10 length is decreased when the vertical spacing is smaller. Since a second edge length 'Y', which is measured along the second edge 24 generally between the top 26 and bottom 28 edges, is maintained constant as the first edge length is changed to accommodate the vertical spacing, spacing of each one of the holes 30 of the stringer plate measured from the bottom edge 28 in a direction along the first edge 22 is

15 maintained constant between implementations of the modular staircase framework.
Each step may further include a riser plate 48. The riser plate generally increases structural strength of the staircase framework. The riser plate spans between the first 18A and second 18B stringer plates in an upright orientation. Each riser plate has opposing top 50 and bottom 52 edges and opposing inner and outer = 20 surfaces 53A and 53B. In the illustrated embodiment, the riser plate overlaps the first edges 22 of the stringer plates so that the inner surface 53A of the riser plate engages the first edges, as more clearly shown in FIG. 6. Also, as more clearly shown in FIG.
7, the top edge 50 of the riser plate is substantially flush with a bottom surface 37A of the tread plate 36 which is over the riser plate. Furthermore, the outer surface 53B of the riser plate at a location along the bottom edge 52 thereof engages the inner edge

16 40 of the tread plate of a lower step with the bottom edge 52 of the riser plate engaging the top edge 26 of the stringer plate thereunder.
Each riser plate defines a plane prior to being flexed across the stringer plates so as to be arced therebetvveen. The riser plates are substantially flexible so that the riser plates can be arced across the steps. As more clearly shown in FIG. 7, each riser plate comprises a plurality of rivets 54 spaced along the top edge 50 of the riser plate for fastening to the tread plate 36 above the riser plate. The rivets project from the top edge in the plane of the riser plate. Accordingly, each tread plate has a plurality of holes 56 spaced along the outer edge 42 of each tread plate which are arranged to receive the rivets of the riser plate therethrough. The holes along the outer edge of the tread plate are spaced inwardly away from the outer edge so as to lie along a contour where the riser plate meets the tread plate along the top edge 50 of the riser plate.
Each riser plate joining tread plates of adjacent steps also has holes 58 spaced along the bottom edge 52 thereof. Accordingly, the tread plate of every step excluding the topmost step has a plurality of rivets 60 projecting from and spaced along the inner edge 40 of the tread plate. The holes 58 along the bottom edge 52 of the riser plate are arranged to receive the rivets 60 of the tread plate therethrough.
The stringer plates 18, tread plates 36, and riser plates 48 are fabricated from flat sheet metal which is cut into appropriate shapes and to have all necessary components (e.g., the tabs, holes, and rivets) using a cutting method controlled by a computer. The cutting method comprises laser cutting in the illustrated embodiment;
in other embodiments, the cutting method comprises plasma cutting. Generally, implementation of the computer to control the cutting of the sheet metal makes fabrication of all the plates more feasible as opposed to casting the plates, especially

17 when each stringer plate may have a different plate width W' and when the first edge length of the stringer plates may be adjusted in order to accommodate the vertical height between upper and lower levels of the particular implementation for which the dimensions of the modular staircase framework were designed. Ornate designs may also be cut into the plates. In order to meet maximum load criteria, thicker (i.e., higher gauge) sheet metal may be used or riser plates may be fabricated in order to strengthen the framework. As such, the computer program manages the fabrication all of the components for the staircase. Each one of the plates is catalogued by the computer program and labelled during the cutting of the plates. An end result of the fabrication of the framework is generally a plurality of flat plates which can be packaged and shipped to the customer, where the staircase is then assembled from the plurality of plates on-site at an intended building location. Note that in the illustrated embodiment the tabs of the stringer plates are not bent as part of the fabrication/manufacturing process, i.e., during a time between cutting the stringer plates and assembly of the framework.
In order to assemble the staircase framework, an installer generally begins with the topmost step 12. The stringer plates 18 are typically mounted to a joist of the upper level. Then, the tread plate 36 is mounted across the stringer plates so as to lie horizontally flush along the top edges 26 thereof as in the illustrated embodiment. Alignment of the tread mounting elements of the stringer plates with the holes 46 along the side edges 38 of the tread plate may necessitate bending of the stringer plates at the coupling elements thereof. As such, this alignment of the tread mounting elements of the stringer plates with the holes 46 along the side edges of the tread plate, for each step, generally dictates proper formation of the curvature of the stringers of the framework 10.

18 After the tread plate of the topmost step is mounted, the riser plate 48 is also installed, if present. During installation of the riser plate, the riser plate is arced across the stringer plates as the rivets 54 along the top edge 50 of the riser plate are aligned with and inserted into the holes 56 along the outer edge 42 of the tread plate.
That is, the riser plate takes on its flexed shape primarily as a result of fitting the rivets 54 of the riser plate into the holes 56 of the tread plate.
After installing the topmost step, the installer continues with the adjacent step, installing each adjacent step one plate at a time and typically starting installation of the adjacent step with attachment of the stringer plates to the stringer plates of an upper step via bolts. Bolting of the stringer plates to those of the upper step is followed by fastening of the tread and riser plates. Installation of the tread plate involves inserting the rivets 60 along the inner edge 40 of the tread plate into the holes 58 of the riser plate of the upper step.
Once assembled, the modular staircase framework 10 of the illustrated embodiment defines a frame of a freestanding staircase. The tread plates may be detached after assembly of the modular staircase framework for sizing and shaping finishing materials to be installed on the tread plates using the tread plates as templates therefor.
It will be appreciated that projection of the tread plate's outer edge 42 beyond the riser plate 48 thereunder may afford sufficient space for this riser plate, which meets the respective tread plate 36 at its bottom surface 37A, to receive a finishing material thereon of appropriate thickness without then protruding beyond the tread plate thereover.
It is important to recognize that since the fabrication process involves cutting of the plates, free of any bending of any of the coupling elements of the

19 stringer plates, it is possible to assemble a mirrored version of the staircase framework which curves in an opposite manner from the initial design by interchanging positions of the first and second stringer plates of each step and mounting the tread plates and the riser plates reversely.
In one other embodiment of the present invention, the tread mounting element is a pair of flanges 62 that are bent at substantially right angles to the stringer plate.
In another embodiment shown in FIG. 9, the framework also includes a plurality of extension plates 64. Each step having stringer plates which are raised from the lower level has a pair of the extension plates. Each extension plate is coupled to a stringer plate 18 so as to extend downwardly therefrom to the lower level. As such, the extension plate spans vertically between a top edge 66 thereof, which is curved to match the bottom edge 28 of the stringer plate to which the extension plate is attached, and a bottom edge 68 of the extension plate that is generally substantially flush with the lower level. Opposing side edges 70 of the extension plates are parallel to one another and typically span a majority of a vertical length of the extension plates. Also, ornate designs may be cut into the extension plates. In general, the extension plates provide support to the stringers and improve the structural strength of the entire staircase framework. Furthermore, the extension plates along each one of the stringers collectively define a wall.
In yet another embodiment shown, a pair of substantially identical staircase frameworks are arranged one over top of another. A first one of the pair of staircase frameworks joins a first level and a second level adjacent thereto and over the first level. A second one of the pair of staircase frameworks joins the second level and a third level adjacent thereto and over the second level. A plurality of elongate structural members span vertically between the staircase frameworks along at least one of the stringers thereof. The elongate structural members, which may comprise studs, are coupled to the stringers along outer surfaces thereof along joints of the stringers which are defined by the coupling element of one stringer plate overlapping 5 the receiving element of an adjacent stringer plate. The bolts for coupling the adjacent stringer plates may also be driven through the studs so that one set of bolts couples adjacent stringer plates and the stud to the stringer at the joint. The studs collectively define a wall framework upon which panels may be mounted for making a wall.
In yet further embodiments in which ornate designs are cut into the riser 10 plates, lighting may be added loran aesthetically pleasing effect.
Further alternative embodiments may include hand rail jigs which are also designed and fabricated by the computer program like the steps of the staircase.
Since various modifications can be made in my invention as herein above described, and many apparently widely different embodiments of same made, 15 it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a limiting sense.

Claims (21)

CLAIMS:

1. A
modular staircase framework for assembly in sections comprising:
a plurality of steps, each step comprising:
a first stringer plate;
a second stringer plate laterally opposite the first stringer plate;
the first and second stringer plates being oriented substantially upright and substantially parallel to one another;
the first and second stringer plates having opposing first and second upright edges; and a tread plate spanning between the first and second stringer plates in a horizontal orientation;
the first stringer plates of the steps collectively defining a first stringer and the second stringer plates of the steps collectively defining a second stringer;
within each pair of adjacent steps, the stringer plates of each respective stringer being aligned so that the first upright edge of the stringer plate of one step is adjacent the second upright edge of the stringer plate of another step;
within at least one pair of adjacent steps:
at least one of the first or second stringer plates of a first step comprising a receiving element at or adjacent the first upright edge thereof;
and at least one of the first or second stringer plates of a second step comprising a coupling element at or adjacent the second upright edge thereof for coupling to the receiving element of an adjacent one of the stringer plates of the first step;
wherein the first and second stringer plates and the tread plate are fabricated from sheet metal using a cutting method controlled by a computer.

2. The modular staircase framework according to claim 1, wherein the cutting method comprises laser cutting or plasma cutting.

3. The modular staircase framework according to claim 1 or 2, wherein the coupling element is overlapping the receiving element along a planar surface of the at least one of the first or second stringer plates of the first step.

4. The modular staircase framework according to any one of claims 1 to 3, wherein the receiving element comprises at least one hole.

5. The modular staircase framework according to claim 4, wherein said at least one hole comprises a plurality of holes along the first upright edge.

6. The modular staircase framework according to any one of claims 1 to 5, wherein the coupling element comprises at least one tab projecting from the second upright edge of said at least one of the first or second stringer plates of the second step, said at least one tab being arranged for overlapping the receiving element.

7. The modular staircase framework according to claim 6, wherein said at least one tab comprises a plurality of tabs along the second upright edge.

8. The modular staircase framework according to any one of claims 1 to 7, wherein the coupling element is bent at an angle from a planar surface of said at least one of the first or second stringer plates of the second step for introducing a curve in the staircase.

9. The modular staircase framework according to any one of claims 1 to 8, wherein the coupling element is integral with said at least one of the first or second stringer plates of the second step.

10. The modular staircase framework according to any one of claims 1 to 9, wherein each one of the first and second stringer plates comprises a top edge spanning between the first and second upright edges thereof, and at least one of the first or second stringer plates includes a tread mounting element at or adjacent the top edge thereof.

11. The modular staircase framework according to claim 10, wherein the tread mounting element comprises at least one flange along the top edge that is arranged for coupling the tread plate thereto.

12. The modular staircase framework according to claim 11, wherein said at least one flange comprises a plurality of flanges along the top edge.

13. The modular staircase framework according to claim 10, wherein the tread mounting element comprises at least one projecting element projecting from the top edge that is arranged for riveting the tread plate.

14. The modular staircase framework according to claim 13, wherein said at least one projecting element comprises a plurality of projecting elements along the top edge.

15. The modular staircase framework according to any one of claims 1 to 14, wherein the first stringer plate has a first plate width measured between the first and second upright edges thereof and the second stringer plate has a second plate width measured between the first and second upright edges thereof, and when the first and second stringers are curved for creating a curved staircase, the first plate width of at least one of the first stringer plates is different from the first plate width of at least another one of the first stringer plates and the second plate width of at least one of the second stringer plates is different from the second plate width of at least another one of the second stringer plates.

16. The modular staircase framework according to claim 1, wherein at least one of the steps further comprises a riser plate spanning between the first and second stringer plates thereof, the riser plate being arranged in an upright orientation between the first and second stringer plates.

17. The modular staircase framework according to claim 16, wherein each one of the first and second stringer plates has opposing top and bottom edges spanning between the first and second upright edges thereof, and the riser plate comprises opposing top and bottom edges spanning between laterally opposing upright side edges of the riser plate, the top edge of the riser plate being arranged at a location closer to the top edges of the first and second stringer plates of the at least one of the steps than to the bottom edges thereof and the top and bottom edges and the upright side edges collectively defining an outer periphery of the riser plate, the riser plate further comprising a plurality of projecting elements along the outer periphery that are arranged for riveting to at least one of the tread plates or to the first and second stringer plates.

18. The modular staircase framework according to claim 17, wherein the projecting elements along the outer periphery of the riser plate comprise projecting elements along the top edge thereof for riveting to said at least one of the tread plates.

19. The modular staircase framework according to any one of claims 16 to 18, wherein each tread plate comprises opposing inner and outer edges spanning between laterally opposing side edges of the tread plate, the inner edge being arranged closer to the second upright edges of the first and second stringer plates of each step than to the first upright edges thereof and the outer edge being arranged closer to the first upright edges of the first and second stringer plates of each step than to the second upright edges thereof, and at least one of the tread plates further comprising a plurality of projecting elements along the inner or outer edge that are arranged for riveting to the riser plate.

20. The modular staircase framework according to claim 19, wherein the projecting elements along the inner or outer edge of the tread plate comprise projecting elements along the inner edge thereof.

21. A modular staircase framework kit for assembly in sections comprising:
a plurality of first stringer plates, a plurality of second stringer plates arranged to be laterally opposite the first stringer plates;
wherein the first and second stringer plates have opposing first and second edges;
wherein the first and second stringer plates are arranged to be substantially upright and substantially parallel to one another;
a plurality of tread plates arranged to span between the first and second stringer plates in a horizontal orientation;
wherein the first stringer plates are arranged to collectively define a first stringer and the second stringer plates of the steps are arranged to collectively define a second stringer;
at least one of the first or second stringer plates comprising holes along the first edge thereof;
at least another one of the first or second stringer plates comprising tabs projecting from the second upright edge thereof for coupling to the holes of said at least one of the first or second stringer plates;
wherein the first and second stringer plates and the tread plates are fabricated from sheet metal using a cutting method controlled by a computer.