A SELF-SUPPORTING SPIRAL STAIRWAY AND A METHOD OF PRODUCING SAME

Abstract: The invention concerns a self-supporting spiral stairway. The object of the invention is to allow construction of a sturdy stairway of this kind, comprising a small number of prefabricated components which are easy to adapt to the conditions prevailing on the building site, e.g. to the available space. A stairway in accordance with the invention is constructed from a vertical screen element (1) which forms the inner bend of the stairway, which is curved in the winding direction of the stairway and which is supported on the ground, from a number of vertical supporting rods which form the outer bend of the stairway and which also are supported on the ground, and from treads (4) arranged in a fan-shape and extending between the screen element and the supporting rods with the tread ends anchored respectively in the screen element and in the supporting rods.

Description: A SELF-SUPPORTING SPIRAL STAIRWAY AND A MET*- .ID OF PRODUCING SAME. The subject invention relates to a self-supporting spiral stairway. The principal purpose is to provide a stairway of th general kind referred to above but which possesses sufficient stability also in cases where it is not anchored to the framing joists or the framework of the building to be fitted with the stairway while at the same time the latter may be easily adapted for accommodation i the space available to erect the stairway. These aspects may be of particular interest when the stairway is to be mounted in older, already existing buildings. This purpose is achieved by means of a stairway of the kind outlined which is constructed from a vertical screen element, which element forms the inner bend of the stairway, which is curved in the winding direction of the stairway and which rests on the ground, from a number of vertical supporting rods which form the outer bend of the stairway and which likewise rest on the ground, and from treads which are distributed in a fan-shape and which extend between the screen element and the supporting rods with their ends secured in respectively the screen element and in the supporting rods. The rods likewise concern a method of erecting a stairway of this kind as is also defined in the appended claims. One embodiment of the invention will be described in closer detail in the following with reference to the accompanying drawings, wherein Fig. 1 is a perspective view of a stairway in accord¬ ance with the invention, Fig. 2. is a cross sectional view through an element incorporated in the stairway, ~Sr < Fig. 3 illustrates a first sequence of the erection of the stairway, Fig. 4 illustrates the next sequence of the erection of the stairway, Fig. 5 illustrates the stairway when the erection thereof has progressed somewhat further, Fig. 6 illustrates the stairway when it is nearing its completed erection, Fig. 7 is a cross section view of an embodiment of the central element intended to form the inner bend of the stairway, Fig. 8 is a corresponding view of a similar central element having a somewhat different shape, and Fig. 9 illustrates schematically a device intended to be used as an aid when erecting the stairway. The stairway illustrated in Fig. 1 is constructed from a vertical screen element 1 which is curved in the winding direction of the stairway and which forms the inner bend of the stairway. The lower end of the screen element rests on the support, e.g. the floor, on which the stairway is installed. In addition, numeral reference 2 designates a number of vertical supporting rods which form the external bend of the stairway and which also are supported on the ground 3. Between the supporting rods 2 and the screen element 1 extend the treads 4 incorporated in the stairway. In accordance with the embodiment shown, the supporting rods 2 extend upwardly, beyond the treads 4, to a handrail level that is suitable for the particular stairway, and at this level the rods support the stairway handrail 5. To reduce the rod spacing and consequently the risk of e.g. objects falling through the gap between the rods, a number of handrail rods 6 are provided so as to alternate with the supporting rods, and in accordance with the embodiment shown these extra rods 6 extend only from the associated tread 4 up to the handrail 5. If required, the handrail rods 6 as well as the supporting rods 2 may, however, continue upwards beyond the handrail, and even into the framing joists positioned in the building at the upper landing of the flight of stairs. The central screen element 1 in accordance with the embodiment shown consists of three part elements desig- nated 1', 1'', and l 1 ' 1 . If desired, the number of such part elements may be smaller or larger. When it is desired to give the stairway a circular circumference and yet vary the walking width of the treads, from the lower landing to the upper landing, the individual part elements may be formed with different curvatures. For instance, the first part element could have a radius of curvature smaller than the last part element, for instance as illustrated in Fig. 7. If desired, the central screen element could of course comprise an even larger number of part elements, as illus- trated in Fig. 8. Also, the screen element may be given a different configuration from that shown. As most clearly apparent from Fig. 2 the part elements preferably are constructed from a number of wooden rods 7, preferably having a slightly wedge-shaped cross-sectional shape, and being covered externally by an inner surface layer 8 and an outer surface layer 9, preferably made from pliable veneeer or the like. In the assembled position of the stairway, the various part elements are bonded together in any suitable manner, such as by glueing, screwing, by means of inter- engaging tongues and grooves, or in some other appropriate way. Alternatively, the joint between the part elements could include a combination of these interconnection methods. As most clearly apparent from sequence figures 3 and 4, the screen element preferably is formed with apertures 10 the shape of which corresponds to the shape of the inner ends 4' of the treads 4. Preferably, also the handrail rods 6 and the supporting rods 2 are formed with apertures or recesses 11 into which project the outer ends 4' ' of the treads. Also the treads could be provided with such apertures or recesses so as to further enhance the strength of the engagement bond. The apertures 10 in the screen element preferably do not extend through the full thickness of the screen element but instead form pockets therein to support the treads. Preferably, the treads are secured in the screen element with the aid of screws 12 screwed into the ends of the treads, if desired in com¬ bination with glueing. Similarly, the treads preferably are attached to the supporting rods 2 and the handrail rods 6. In case the supporting rods and the handrail rods project beyond the level of the handrail 5, the latter preferably abuts against the individual rods with a suitable spacer means inserted therebetween, allowing the persons using the stairs- to unimpedely grip the upper handrail part. The treads as well as the supporting rods and the handrail rods may be delivered to the building site in one or only a few standard lengths and be cut as desired. Above all, it is the inner tread ends that are cut. In accordance with the embodiment shown, each support rod 2 is attached to and supports respectively the front edge and the rear edge of two adjacent treads. This arrangement imparts excellent strength to the construction and in combination with the central curved screen element, it allows the stairway to stand freely without becoming instable. It goes without saying, that this does not exclude anchorage of the stairway in the framing joists of the building or in other structural framework parts thereof. Numeral reference 13 designates borders depending below the front edge portion or nosing of the treads and, like the handrail rods 6, serving as a fall-through prevention means. The borders 13 obviously also have the effect of increasing the bending resistance of the treads. The stairway preferably is erected in the following manner. Initially, one or several joined-together screen elements 1' — 1' ' ' are erected, said elements either having previously been provided with the recesses 10 or else such recesses are formed therein on the site. Alternatively, other types of supports and index markings for locating the treads are provided. The recesses 10 preferably are made with the aid of a master template of the kind illustrated in Fig. 9, in which the sizes and positions of the recesses are indicated. In Fig. 3 is illustrated the start of the erection of the stairway, with the first tread secured in the screen element 1' and one support rod 2 mounted in position. For illustrative purposes, the second tread is shown in an exploded view. Fig. 4 illustrates the four first treads secured to the screen element 1 as well as to the associated supporting rods 2 whereas the fifth and the sixth treads are shown in exploded views together with the screen element 1 and the associated support rods 2. The mounting of the stairway preferably continues in the same manner, as illustrated in Fig. 5. It is also possible to mount the treads in their associated part element l'-l-'', whereupon stairway elements interconnected by means of their respective part elements are assembled and the part elements are inter¬ connected. This method is only possible, however, when sufficient space is available to allow the parts to be moved relatively one another. In narrow spaces, it is preferred to start mounting the different treads only when the assembly of the various part elements of the screen is completed. If the handrail is not manufactured previously in accordance with a suitable pattern, it may be manufactured in situ, as appears from Fig. 6. In this case, the hand- rail 5 preferably is made from a number of thin lamellae strips which are deposited along the stairway and which are clamped with the aid of vices against the supporting rods and handrail rods. The handrail preferably is con¬ structed from a number of thin and comparatively pliable layers which are positioned one on top of the other with intermediary layers of glue. When hardening in the hand¬ rail thus shaped is completed, the handrail is lifted and is secured in position at the desired level, as appears from Fig. 1. The handrail preferably is screwed to the supporting rods and the handrail rods. When these rods terminate level with the handrail they may abut flush against the latter but when they continue past the handrail some spacer means preferably is positioned between the rods and the handrail. By suitable choice of the part elements of the screen element 1 it becomes possible, according to wish, to pro- duce a stairway that is spiral or symmetrically rounded, steep or flat, wide or narrow. The central screen element is the major load-carrying component of the construction and whenever desired, it* may also serve as a load-carrying or supporting wall between the planes of extension of the stairway. In addition to its normal handrail function, the handrail 5 also is effective to interconnect and immobilize the rods and thus give the stairway additional stability. The bow that the handrail forms and that pre- ferably consists of glued wood veneer could either be manufactured according to a pattern at full scale in series production or else, as described in the aforegoing, in the case of special designs, be built in situ when the stairway is erected. Preferably, the handrail is constructed from full- width strips of two-layer plywood and is glued as described above, preferably in superposed layers with the joints displaced. Owing to the external circular configuration of the stairway in combination with an ergonomically tested riser height the stairway may easily be given optimum walking- geometry characteristics. The stairway structure also allows the tread blanks, the screen element and the rods to be prefabricated to an extensive degree. After fasten- ing of the treads in the central screen element 1 visible screw heads, if any, may be concealed by applying a pliable board on the face of the screen element 1 facing away from the stairs. The invention is not limited to the embodiment illustrated in the drawing figures but could be modified in a variety of ways as to its details within the scope of the appended claims.

Claims: CLAIMS 1. A self-supporting spiral stairway, c h a r - a c t e r i z e d in that it consists of a vertical screen element (1), said screen element forming the inner bend of the stairway, being curved in the winding direc¬ tion of the stairway, and resting on the ground, of a number of vertical supporting rods (2), said supporting rods forming the outer bend of the stairway and likewise resting on the ground, and of treads (4), said treads being arranged in a fan-shape and extending between the screen element (1) and ■ fche supporting rods (2) with their ends secured respectively in the screen element and in the supporting rods. 2. A stairway as claimed in claim 1, c h a r a c¬ t e r i z e d in that each one of at least some of the supporting rods (2) supports two treads (4) in succession, preferably at the rear edge of one tread and at the front edge of the following tread positioned at a higher level. 3. A stairway as claimed in claim 1 or 2, c h a r ¬ a c t e r i z e d in that the supporting rods (2) are extended above the treads (4) up to at least the level of the handrail, where they support a handrail (5) extending along the external bend of the stairway. 4. A stairway as claimed in claim 3, c h a r a c¬ t e r i z e d in that the supporting rods (2) project upwards to the level of the overhead framing joists to allow anchoring of said rods therein. 5. A stairway as claimed in any one of the pre¬ ceding claims, c h a r a c t e r i z e d in that the central screen element (1) exhibits a varying curvature in order to vary the width of the stairway and thus, if needed, to accommodate the stairway to the space available therefor. 6. A stairway as claimed in any one of the pre¬ ceding claims, c h a r a c t e r i z e d in that the central screen element (1) is composed of a number of part elements (1' - 1' ' ' ) which are distributed around the circumference of the screen. 7. A stairway as claimed in claim 6, c h a r a c¬ t e r i z e d in that the part elements of the screen (1) are bent to a curvature corresponding to an arch of a circle, and in that the individual radii of curvature of the part elements vary. 8. A stairway as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the treads (4) project into -recesses (10) formed in the screen element (1), the cross-sectional configuration of said receses corresponding to that of the tread ends. 9. A method of constructing a spiral stairway, c h a r a c t e r i z e d by erecting centrally a screen element which is curved in the winding direction of the stairway and the curvature of which is chosen in dependence of the availabe space and possibly also in dependence of the desired treaad width of the stairway, and by attaching suitable lengths of severed treads in succession respectively in the screen element in the inner bend of the stairway and in vertical supporting rods (2) in the outer bend of the stairway, said rods resting on the ground. 10. A method as claimed in claim 9, c h a r a c ¬ t e r i z e d by assembling the screen element (1) on the building site from part elements, if desired after assembly of the associated treads (4) and supporting rods (2).

Inventors: STAALHANE HENRIK, STAALHANE-BJOERNBERG MARIA, STAALHANE, HENRIK, STAALHANE-BJOERNBERG, MARIA
Applicants: STAALHANE BJOERNBERG MARIA, STAALHANE HENRIK, STAALHANE, HENRIK, STAALHANE-BJOERNBERG, MARIA
Application year: 1991
Main classification: E04F11
IPC codes: E04F11