WO2024014954A1

WO2024014954A1 - A modular staircase

Info

Publication number: WO2024014954A1
Application number: PCT/NL2023/050378
Authority: WO
Inventors: Johannes Peter VAN DRIEL
Original assignee: Verberne Gijs
Current assignee: Verberne Gijs
Priority date: 2022-07-15
Filing date: 2023-07-13
Publication date: 2024-01-18
Anticipated expiration: 2025-01-15
Also published as: EP4555158A1

Abstract

A modular staircase (1) comprising stair tread modules (9, 9', 9") together at least forming a backbone of the staircase (1), wherein the stair tread modules (9, 9', 9") each have an orientation and the respective orientations of the stair tread modules (9, 9', 9") are adjustable with respect to each other in order to tailor and dedicate the modular staircase (1) to a particular location or application. The stair tread modules (9, 9', 9") comprise essentially horizontal elements (2, 2', 2'') configured as steps of the staircase (1) and connecting elements (3, 4, 5) for connecting steps at neighbouring levels of the staircase (1) to each other.

Description

A MODULAR STAIRCASE

TECHNICAL FIELD

The invention relates to a modular staircase comprising stair tread modules together at least forming a backbone of the staircase.

BACKGROUND ART

There is a need for a modular staircase which can be easily tuned to dimensions accurately fitting in a location where the staircase is to be mounted. In practice with existing staircases there is always an inaccurate dimensioning of the staircase requiring finishing work on the staircase after it is mounted to remove play between the staircase and the construction of the building where the staircase is mounted.

US5907935A discloses a modular and adjustable staircase for being installed between floor levels of different heights, and including stairs allowing passage from one level to the other, said staircase comprising:

(a) a rail stiffener located on at least one side of the staircase;

(b) at least one vertical piece having top and bottom ends, the top end being secured to the stiffener and the bottom end extending downwardly towards the stairs and having at least one crosspiece-receiving opening therein; and

(c) a stair-supporting crosspiece with an enlarged heel received within the opening of said vertical piece, said heel determining the relative height of a stair supported by said crosspiece.

US5613341A discloses a method of building a staircase comprising: moulding a supply of one-piece stair modules, each said module having a front wall and a back wall; and attaching a required number of one-piece stair modules together to form a staircase by inserting at least one connector through a front wall of a first module and a rear wall of a second module.

ES2235674 discloses compensated stairs having multiple identical steps formed by a flat rhombic area, an angular triangular back, a vertical cylindrical column and an L-shaped inferior support with side flaps reinforcement. The steps are reconciled by screws and by superposition of the vertical cylindrical column and the L-shaped inferior support in curvilinear zones of the stairs using diametrical entrants and projections in a superposition zone with angular deviations between each pair of determined steps.

SUMMARY OF INVENTION

It is an object of the invention to provide a more versatile modular staircase which can be easily accommodated to very different locations and different dimensions, and yet providing top-notch finishing without noticeable play between the modular staircase and the building construction where the staircase is established.

According to the invention a modular staircase comprising stair tread modules together at least forming a backbone of the staircase is proposed, having features according to one or more of the appended claims.

In a first aspect of the invention the stair tread modules each have an orientation and the respective orientations of the stair tread modules are adjustable with respect to each other in order to tailor and dedicate the modular staircase to a particular location or application. Furthermore, the used stair tread modules allow the modular staircase to be dismantled and reused in another application with totally different dimensions for placement of the staircase.

Suitably, each of the stair tread modules comprises an essentially horizontal top side configured as tread of the staircase and an essentially horizontal bottom side configured as base of the stair tread module. The top side comprises at least one straight slit to provide that two stair tread modules coupled together are translatable with respect to each other. The bottom side comprises a rotation opening whose midpoint defines an axis of rotation of the stair tread module. At least one connecting pin received in both the rotation opening of a first stair module and the at least one the straight slit of a second stair module corresponding to the rotation opening, enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module, and allows the first stair module and the second stair module to be securely attached to each other.. Having at least one connecting pin through both at least one straight slit in the top side and a rotation opening in the bottom side for adjustable connection provides the staircase according to the subject technology with a high degree of flexibility in tailoring the staircase to the envisaged location or application. When the at least one connecting pin between stair tread modules is provided but not fastened in the rotation opening and straight slit, a flexible backbone of a staircase is formed. In this case, the at least one straight slit allows two successive steps of the staircase to shift horizontally relative to each other in the direction of the slit and the rotation opening enables rotation of two successive step relative to each other, so that deviations in the dimensions and position of the floor opening can be corrected by translating and/or rotating stair tread modules of the modular staircase relative to each other. The non-fastened connecting pins ensure that the stair tread modules are flexibly connected to each other. When all connecting pin between all stair tread modules are fastened, a rigid backbone of a staircase is provided.

In an embodiment, the bottom side further comprises at least one section of a circular slit coinciding with a circle having a centre coinciding with the axis of rotation. The at least one section of a circular slit of the first stair tread module corresponds to the at least one straight slit in the second stair tread module. At least one connecting pin received in both the at least one section of a circular slit of the first stair module and the at least one the straight slit of the second stair module corresponding to the at least one section of a circular slit, enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module, and allows the first stair module and the second stair module to be securely attached to each other. These features allow for an even more secure attachment of the two modules, preventing any shifting or rotating relative to each other. Although more pins are provided in the straight slits and corresponding rotation opening and at least one slit shaped like part of a circle, this does not make rotating and translating two modules relative to each other more difficult.

In a further embodiment, the bottom side of the first stair tread module is provided with two sections of circular slits on opposite sides of the rotation opening. Said sections of circular slits in the circular disk corresponding to straight slits in the top side of the second stair tread module. Connecting pins received in the circular slits and corresponding straight slits enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module and allows the first stair module and the second stair module to be securely attached to each other. The more connecting pins are used, the more securely two modules can be attached to each other, without making the rotating and translating two modules relative to each other more difficult.

In an embodiment, a first pin of the at least one connecting pin has a cross section that matches the rotation opening in the bottom side and passes through both the rotation opening of the first stair tread module and one of the at least one straight slit of the second stair tread module. In this embodiment, the first pin functions as a rotation shaft to rotate stair tread module relative to each other.

In an alternative embodiment, the modular stair case further comprises upper clamping elements, wherein the upper clamping elements are provided with one or more openings corresponding to the at least one straight slit of said top side of said stair tread module. Connecting pins received in the one or more openings of the upper clamping elements, the circular rotation opening, and said corresponding straight slits enable the bottom side of said first stair module to be clamped between said upper clamping element and the top side of the second stair tread module. These features allow for a firm coupling of modules using just one rotation opening in the bottom surface of a module, preventing two modules from rotating relative to each other. This is because the surfaces of the bottom and top, which are pressed against each other with force by fastening the connections pins, are located at some distance from the axis of rotation. The generated frictional forces make it harder to rotate the modules relative to each other, requiring more torque to do so.

In a further embodiment, the modular stair case further comprises intermediate disc parts. The intermediate disc parts are provided with one or more openings corresponding to the one or more openings of the upper clamping elements, wherein the intermediate disc part fits into the rotation opening of the bottom side of corresponding stair tread modules, allowing the bottom side of the first stair module to move around the axis of rotation relative to the top side of the second stair module. With these features, a first module placed on a second module can only be rotated around the axis of rotation defined by the rotation opening in the bottom surface of the first module and shifted in the direction of the straight slits in the top side of the second module. Advantageously, the intermediate disc parts have a thickness that is smaller than the thickness of the bottom side of a stair tread module.

In an embodiment, the essentially horizontal top side and an essentially horizontal bottom side coupled together by a number of rigid strips. In an alternative embodiment, the essentially horizontal top side and an essentially horizontal bottom side coupled together by at least one tubular element. In a further embodiment, the essentially horizontal top side and an essentially horizontal bottom side coupled together by are coupled together by two nested tubular elements. The features of the latter embodiment, allows adapting the rise height of the stair tread module.

In an embodiment, the essentially horizontal top side and an essentially horizontal bottom side are formed from a single plate by bending the plate. In this way, a stair tread module can be produced in a cost-effective way.

In an embodiment, the modular staircase further comprises flat spacer elements arranged between stacked stair tread modules. This feature allows adapting the rise height of two coupled stair tread modules in a simple and cost-effective way.

Suitably the stair tread modules comprise essentially horizontal elements configured as steps of the staircase and connecting elements for connecting neighbouring steps, i.e. steps at neighbouring levels, of the staircase to each other. This enables an easy build-up of the staircase of the invention.

Beneficially the stair tread modules comprise a circular disk mountable on top of another stair tread module. This circular disk provides the staircase of the invention with a high degree of flexibility in tailoring the staircase to the envisaged location or application.

In one preferred embodiment the circular disk is provided with a center opening, said center opening corresponding to a straight slit in the top side of the another stair tread module, and said center opening and said straight slit receiving a connecting pin, so as to provide that the circular disk is translatable and rotatable with respect to the another stair tread module.

It is further preferred that the circular disk supports a first tube which is arranged to cooperate and snugly fit into or around a second tube which is connected to a second step above the first step on which the circular disk is mounted. This further promotes the flexibility of the staircase of the invention, in particular when navigating the staircase through bends. In that situation it is particularly desirable that the first tube and the second tube have a circular crosssection, to enable that the first tube and the second tube, and therewith the steps at different levels of the staircase are rotatable with respect to each other.

According to another embodiment the first tube and the second tube are rotationally fixed with respect to each other, wherein the circular disk is provided with sections of circular slits on opposite sides of the center opening, said sections of circular slits in the circular disk corresponding to straight slits in the first step, said circular slits of the circular disk and said straight slits in the first step receiving a connecting pin or pins, so as to provide that the first tube which is supported by the circular disk is translatable and rotatable with respect to the first step. Also this embodiment enables the staircase of the invention to easily navigate through desired bends of the staircase.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects, properties and advantages will be explained hereinafter based on the following description with reference to the drawings, wherein like reference numerals denote like or comparable parts, and in which:

Figure 1 shows a modular staircase according to the invention;

Figure 2 shows a section of the modular staircase shown in figure 1 ;

Figure 3A illustrates translational capabilities of coupled stair tread modules;

Figure 3B illustrates rotational capabilities of coupled stair tread modules;

Figure 4 shows a sheet for producing a second embodiment of a stair tread module;

Figure 5 shows the second embodiment of a stair tread module;

Figure 6 shows a third embodiment of a stair tread module;

Figure 7 shows a fourth embodiment of a stair tread module;

Figure 8A illustrates an exploded view of an embodiment of a coupling system; and, Figure 8B illustrates a top view of the coupling system shown in

Figure 8A.

Whenever the same reference numerals are applied, these numerals refer to the same or similar parts.

DESCRIPTION OF EMBODIMENTS

It is noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms "upward", "downward", "below", "above", and the like relate to the embodiments as oriented in the drawings, unless otherwise specified or functionally required. Further, elements that are at least substantially identical or that perform an at least substantially identical function are denoted by the same numeral.

Figure 1 provides a view at the modular staircase 1 of the invention with a series of stair tread modules 9 forming steps or horizontal sides 2. The stair tread modules together at least forming a backbone of the staircase 1.

Figure 2 shows a detailed view at a section of the modular staircase 1 comprising separable stair tread modules 9 comprising elements 2, 3, 4, 5. The elements 2, 3, 4, 5 together form a stair tread module. The shown backbone - which is completely shown in figure 1- can be completed with facings or covering plates as desired. It is also possible to use the backbone of the staircase 1 as the actual staircase, without further facings or covering plates which are usually applied for aesthetic reasons only.

Figure 2 shows a floor plate 8 fixed to the floor, a first stair tread module 9’ and a second stair tread module 9”. It is particularly desirable that the stair tread modules 9 comprise an essentially horizontal top side 2, 2’, 2” configured as steps of the staircase 1 , an essentially horizontal bottom side 3 and connecting elements 4, 5 for connecting rigidly the top side to the bottom side. Neighbouring stair tread modules form steps that are situated at different heights or levels of the staircase 1.

Figure 2 shows that a first embodiment of the stair tread modules comprises a circular disk to form the bottom side 3. The bottom side 3 is mountable on top side 2’of the first stair tread 9’. The circular disk 3 is provided with a center opening 3’, said center opening 3’ corresponding to a straight slit 6 in the top side 2’ of the first stair tread module 9’. Said center opening 3’ and said straight slit 6 receiving a connecting pin (not shown), so as to provide that the circular disk 3 is translatable and rotatable with respect to the top side 2’ of the first stair tread module 2’. This promotes the flexibility and versatility enabling accommodation and placement of the modular staircase of the invention at any feasible location.

In one embodiment a first tube 4 is connected on top of the circular disk 3 to support the first tube 4. The first tube 4 is arranged to cooperate and snugly fit into (or - in a not shown embodiment - to fit around) a second tube 5 which is connected to a top side 2 of a top side 2” of a second stair tread module 9” above the fop side 2’ of the first stair tread module 9’ on which the circular disk 3 is mounted. In the shown embodiment the first tube 4 and the second tube 5 have a circular cross-section, enabling easy adjustment by applying an angular adjustment of the respective steps 2’, 2” with respect to each other. In the embodiment shown the essentially horizontal top side and an essentially horizontal bottom side are coupled together by two nested tubular elements 4, 5. Another advantage of two nested tubular elements is that allows for adapting the height of a stair tread module.

In another yet not completely shown embodiment it is possible that the first tube 4 and the second tube 5 are rotationally fixed with respect to each other. Then it is desirable that the circular disk 3 is provided with sections of circular slits 3” on opposite sides of the center opening 3’, said sections of circular slits 3” in the circular disk 3 corresponding to straight slits 7 in the first step 2’, wherein said circular slits 3” of the circular disk 3 and said straight slits 7 in the top side of the first stair tread module 2’ receive a connecting pin or pins (not shown), which construction enables that the first tube 4 which is supported by the circular disk 3 is translatable and rotatable with respect to the first step 2’.

With particular reference to figure 3A and 3B, it is shown that the stair tread modules 9 have a particular orientation with respect to each other. It belongs to the essence of the invention that the respective orientations of the stair tread modules 9 are adjustable with respect to each other in order to tailor and dedicate the modular staircase of the invention to a particular location or application. Figure 3A illustrates the translational capabilities of stair tread modules by means of a top side structure 20. The top side structure comprises three parallel straight slits in the top side 2 of the stair tread module 9. The straight slits allow varying the tread depth of the steps between a minimum depth TL1 and a maximum depth TL2. The slits are parallel to each other and perpendicular to the nose edge 21 of the top side 2. This feature allows for changing the tread depth of the steps and consequently the total run of a straight staircase.

Figure 3B illustrates the rotational capabilities of coupled stair tread modules by means of a bottom side structure 30 in the bottom side 3 of a stair tread module 9. The bottom side structure 30 comprises two sections of circular slits 3” coinciding with a circle having a centre and a radius and a central opening 3’ coinciding the centre of the circle. The central opening is configured for receiving a central connecting pin (not shown) to provide that two stair tread modules coupled together are rotatable with respect to each other about an axis defined by the central connecting pin. The three parallel straight slits 6, 7 of the bottom side structure have a mutual distance corresponding to the radius of the circular slits 3”. The two sections of circular slits 3” are configured for receiving corresponding connecting pins to provide that two stair tread modules coupled together are rotatable with respect to each other about an axis defined by the centre of the circle.

It should be noted that in principle one slit and one central opening is sufficient to provide the flexibility needed to adapt the staircase to tune to dimensions accurately fitting in a location where the staircase is to be mounted. However, by using more than one slit and matching bottom side structure and corresponding number of connecting pins, the stair tread modules can be more firmly attached to each other. In an embodiment, the bottom side structure comprises only the two sections of circular slits and the top side structure 20 comprises two parallel slits with a mutual distance of 2 times the radius of the two sections of circular slits in the bottom side structure 30. In another embodiment, the bottom side structure 30 comprises a central opening and one section of a circular slit corresponding to a circle having a radius R. It might be clear to the person skilled in the art that the corresponding top side structure comprises two parallel straight slits with a mutual distance of R. The number of sections of circular slits is not limited to two, but can also be three, four or more. However, this reduces the rotational range to rotate two stair tread modules relative to each other, as the length of the circular slits will be shorter. Preferably, all circular slits have the same length.

Figure 4 shows a sheet for producing a second embodiment of a stair tread module. The sheet allows folding a stair tread module from one piece of metal sheet. After folding we will obtain a stair tread module as shown in figure 5. After bending the sheet, two edges 41 have to be coupled to corresponding two edges 31 of the part of the sheet forming the bottom side 3 of the stair tread module.

Figure 6 shows a third embodiment of a stair tread module. In this embodiment the essentially horizontal top side 2 and an essentially horizontal bottom side 3 are coupled together by a number of rigid strips 60.

Figure 7 shows a fourth embodiment of a stair tread module. In this embodiment, the stair tread module is made from a number of beam-shaped tubes which are coupled together. In a top side of a horizontal tube 70, the top side structure is arranged. A closed end of a vertical tube 71 forms the bottom side 3 of the stair tread module. The bottom side structure 30 is formed in the bottom side of the vertical tube 71. The stair tread module further comprises two essentially horizontal side tubes 73. A backbone of a stair case obtained with stair tread modules according to the fourth embodiment should be covered with decorating elements or covering elements to obtain a usable and save stair case.

Figure 8A illustrates an exploded view of an embodiment of a coupling system to coupled two stair tread modules. It illustrates the top side 2 of a first stair tread module, the bottom side 3 of a second stair tread module to be positioned on the top side 2 of first stair tread module. The top side comprises three parallel straight slits 6, 7. The bottom side 3 comprises one circular rotation opening 311. The circular rotation opening 311 has a diameter such that connecting pins through the straight slits also pass through the circular rotation opening 311. In Figure 8A the connecting pins are four bolts 84.

The top side 2 and bottom side 3 are coupled together by a lower clamping element 81 and an upper clamping element 83. An intermediate disc element 82 has a diameter smaller the diameter of the circular rotation opening to fit into the circular rotation opening 311. Furthermore, the intermediate disc element 82 has a thickness smaller than the thickness of the bottom side 3. The outer edge 88 of the lower clamping element 81 and the outer edge 87 of the upper clamping element 83 protrudes beyond the inner edge 85 formed by the circular rotation opening 311 in the bottom side 3 of a stair tread module. The lower clamping element 81 , the intermediate disc element 82 and upper clamping element 83 have corresponding openings 811 , 821 , 831 to accommodate bolts 84. By screwing nuts on the bolts, the top side 2 and bottom side 3 are clamped between the upper clamping element 83 and lower clamping element 81. The intermediate disc element 82 placed in the circular rotation opening 311 allows the bottom side 3 of the stair tread module to rotate. The annular rim formed by the bottom side 3 located between the upper clamping element 83 and lower clamping element 81 is pressed against the upper side 2 when nuts (not shown) are tightened on the bolts 84. Frictional forces between the respective sides of the clamped parts prevent movements of the coupled stair tread modules relative to each other.

Figure 8B illustrates a top view of the coupling system shown in Figure 8A. Shown are the translational movement and rotational movement of the top side 2 and the bottom side 3 with respect to each other. The outer edges 87, 88 of the upper clamping element 83 and lower clamping element 81 , respectively, coincide. The dashed circle corresponds to the inner edge 85 of the bottom side formed by the circular rotation opening 311 and the outer edge 86 of the intermediate disc element 82. The area between the dashed line circle and the solid line circle is the area at which the top side and bottom side are pressed against each other.

It should be noted that in the coupling system described above. The stair tread module has a to side structure comprising three straight parallel slits 6,7 and the stair tread module has a bottom side structure consisting of one large central opening.

Furthermore, the intermediate disc element 82 has a thickness smaller than the bottom side 3 of a stair tread module to ensure that the bottom side of a stair tread module is sufficiently clamped between upper clamping element and upper side of the stair tread module. In the case where at least three connecting pins are provided in the rotation opening that lie with a side almost against the inner wall of the rotation opening, an intermediate disk element is not always necessary to obtain sufficient clamping to hold the modules stably against each other and to deflect the top clamping element while securing the connecting pins while providing the functionality is easy rotating and translating of two modules relative to each other while the connecting pins are in the rotation opening.

It should be noted that the upper clamping element and intermediate disc element may be combined into a single component. Furthermore, the bottom clamping element is not an essential element for easily rotating and translating two modules relative to each other. It can push the top side and bottom side more firmly together if necessary.

In an alternative coupling system, the top side structure comprises 2 parallel slits. Each of the lower clamping element, the intermediate disc element and upper clamping element comprises 4 corresponding openings. After positioning bolts in the corresponding openings, two bolts are positioned in the first slit of the 2 parallel slits and the other two bolts are positioned in the second slot of the 2 parallel slits.

The embodiment of stair tread modules shown if figure 1 and 2 with two nested tubular elements 4, 5 allows changing the height of a stair tread module. If the top side 2 and the bottom side 3 are coupled together by a single tubular element, the height is fixed. In the embodiments shown in figures 5, 6 and 7, the height of the stair tread modules is also fixed. To be able to increase the rise between the top sides of two coupled stair tread modules, a flat spacer element can be used. The thickness of the spacer element together with the height of the stair tread module will define the rise.

In the embodiments described above the top side comprises a structure to allow two coupled stair tread modules to be translatable relative to each other before the two stair tread modules are fastened together by fastening means and the bottom side comprises a structure to allow two coupled stair tread modules to be rotatable relative to each other before the two stair tread modules are fastened together by fastening means. It is also possible to obtain a staircase having a similar functionality wherein the top side comprises a structure that provides the rotational function and the bottom side comprises a structure to provide the translational function. The presented subject technology makes it possible to use the stair tread modules to create any kind of staircase shape, such as straight stairs, spiral staircase and winder staircase.

Embodiments of the present invention can include every combination of features that are disclosed herein independently from each other. Although the invention has been discussed in the foregoing with reference to exemplary embodiments of the invention, the invention is not restricted to the particular embodiments which can be varied in many ways without departing from the invention. The discussed exemplary embodiment shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiment is merely intended to explain the wording of the appended claims without intent to limit the claims to this exemplary embodiment. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using this exemplary embodiment.

Variations and modifications of the present invention will be obvious to those skilled in the art and it is intended to cover in the appended claims all such modifications and equivalents. The entire disclosures of all references, applications, patents, and publications cited above are hereby incorporated by reference. Unless specifically stated as being “essential” above, none of the various components or the interrelationship thereof are essential to the operation of the invention. Rather, desirable results can be achieved by substituting various components and/or reconfiguration of their relationships with one another.

Claims

CLAIMS:

1. A modular staircase (1) comprising stair tread modules (9) together at least forming a backbone of the staircase (1), characterized in that the stair tread modules (9) each have an orientation and that the respective orientations of the stair tread modules (9) are adjustable with respect to each other in order to tailor and dedicate the modular staircase (1) to a particular location or application.

2. The modular staircase of claim 1 , characterized in that each of the stair tread modules (9) comprises an essentially horizontal top side (2, 2’, 2”) configured as tread of the staircase (1) and an essentially horizontal bottom side (3) configured as base of the stair tread module, wherein the top side comprises at least one straight slit (6, 7) to provide that two stair tread modules coupled together are translatable with respect to each other, wherein the bottom side comprises a rotation opening (3’) whose midpoint defines an axis of rotation of the stair tread module, wherein at least one connecting pin received in both the rotation opening (3’) of a first stair module and the at least one the straight slit (6) of a second stair module corresponding to the rotation opening (3), enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module, and allows the first stair module and the second stair module to be securely attached to each other.

3. The modular staircase according to claim 2, wherein the bottom side further comprises at least one section of a circular slit (3”) coinciding with a circle having a centre coinciding with the axis of rotation, wherein the at least one section of a circular slit of the first stair tread module corresponds to the at least one straight slit in the second stair tread module, wherein at least one connecting pin received in both the at least one section of a circular slit of the first stair module and the at least one the straight slit of the second stair module corresponding to the at least one section of a circular slit, enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module, and allows the first stair module and the second stair module to be securely attached to each other.

4. The modular stair case according claim 3, wherein the bottom side of the first stair tread module is provided with two section of circular slits on opposite sides of the rotation opening, said sections of circular slits in the circular disk corresponding to straight slits in the top side of the second stair tread module, wherein connecting pins received in the circular slits and corresponding straight slits enables the bottom side of the first stair module to be translated and rotated around the axis of rotation relative to the top side of the second stair module and allows the first stair module and the second stair module to be securely attached to each other.

5. The modular stair case according to any of the claims 2 - 4, wherein a first pin of the at least one connecting pin has a cross section that matches the rotation opening in the bottom side and passes through both the rotation opening of the first stair tread module and one of the at least one straight slit of the second stair tread module.

6. The modular stair case according to any of the claims 2 - 4, wherein the modular stair case further comprises upper clamping elements (83), wherein the upper clamping elements are provided with one or more openings corresponding to the at least one straight slit of said top side of said stair tread module, wherein connecting pins received in the one or more openings of the upper clamping elements, the circular rotation opening, and said corresponding straight slits enable the bottom side of said first stair module to be clamped between said upper clamping element and the top side of the second stair tread module.

7. The modular stair case according to claim 6, wherein the modular stair case further comprises intermediate disc parts (82), wherein the intermediate disc parts are provided with one or more openings corresponding to the one or more openings of the upper clamping elements, wherein the intermediate disc part fits into the rotation opening of the bottom side of stair tread modules, allowing the bottom side of the first stair module to move around the axis of rotation relative to the top side of the second stair module.

8. The modular stair case according to claim 7, wherein the intermediate disc parts have a thickness that is smaller than the thickness of the bottom side of a stair tread module.

9. The modular staircase according to any of the claims 2 - 8, wherein the essentially horizontal top side and an essentially horizontal bottom side coupled together by a number of rigid strips.

10. The modular staircase according to any of the claims 2 - 9, wherein the essentially horizontal top side and an essentially horizontal bottom side coupled together by at least one tubular element or by two nested tubular elements.

11. The modular staircase according to any of the claims 2 - 8, wherein the essentially horizontal top side and an essentially horizontal bottom side are formed from a single plate by bending the plate.

12. The modular staircase according to any of the claims 1 - 11 , further comprising flat spacer elements arranged between stacked stair tread modules.

13. The modular staircase of claim 1 , characterized in that the stair tread modules (9) comprise essentially horizontal elements (2, 2’, 2”) configured as steps of the staircase (1) and connecting elements (3, 4, 5) for connecting steps at neighbouring levels of the staircase (1) to each other.

14. The modular staircase of claim 13, characterized in that the stair tread modules (9) comprise a circular disk (3) mountable on top of a first step (2’) of the staircase (1).

15. The modular staircase of claim 14, characterized in that the circular disk (3) is provided with a center opening (3’), said center opening (3’) corresponding to a straight slit (6) in the first step, said center opening (3’) and said straight slit (6) receiving a connecting pin, so as to provide that the circular disk (3) is translatable and rotatable with respect to the first step (2’).

16. The modular staircase of claim 14 or 15, characterized in that the circular disk (3) supports a first tube (4) which is arranged to cooperate and snugly fit into or around a second tube (5) which is connected to a second step (2”) above the first step (2’) on which the circular disk (3) is mounted.

17. The modular staircase of claim 15 or 16, characterized in that the first tube (4) and the second tube (5) have a circular cross-section.

18. The modular staircase of claim 15 and 16, characterized in that the first tube (4) and the second tube (5) are rotationally fixed with respect to each other, and the circular disk (3) is provided with sections of circular slits (3”) on opposite sides of the center opening (3’), said sections of circular slits (3”) in the circular disk (3) corresponding to straight slits (7) in the first step (2’), said circular slits (3”) of the circular disk (3) and said straight slits (7) in the first step (2’) receiving a connecting pin or pins, so as to arrange that the first tube (4) which is supported by the circular disk (3) is translatable and rotatable with respect to the first step (2’).