The present invention concerns a stairway and a method for installing the stairway, wherein the stairway comprises at least one stair tread and means for bearing the at least one stair tread. The stairway according to the invention has primarily been designed for use in terrain, but might also be used for example in connection with a building, for example as a permanent or temporary solution.

The term stairway is used in this document to refer to a device that leads up or down in height in places where an inclination or a ramp would be impractical. In its simplest form, the stairway according to the invention comprises only one tread, wherein the tread is arranged to form a landing or platform to form a substantially horizontal portion over a base. The base may for example be a terrain so that the tread or platform makes it safer for humans to move between different levels in the terrain. Alternatively, the base may be a foundation outside of or within a building so that the stair tread forms an elevation or a platform that rises above the foundation.

The publications KR 20190131344 A, CN1 13445683 A and CN206752894 disclose stairway solutions wherein the stair treads are borne by bearing rods that extend to a foundation. The bearing rods are connected to the stair treads through a bearing construction. The bearing rods are arranged on an exterior of the stair treads' side portions.

The stairway according to the invention is preferably, but not exclusively, produced of metal, wherein the one or each of the stairway's stair treads has a run or a tread portion that is delimited by a nose portion, a rear portion opposite the nose portion, and two side portions. The stair tread may in some embodiments be provided with friction-increasing means. A tread portion designed as a grate is one example of a stair tread with a suitable friction-increasing means.

Even though the stairway according to the invention may be made up of only one tread, the description below is primarily directed at a stairway that has at least two stair treads.

Installing a stairway in terrain can be challenging. The terrain in which the stairway is to be installed, may have varying slope angles along the flight of the stairway, which may make it necessary to prepare the terrain before the stairway is disposed against the terrain.

Such a preparation of the terrain may be especially challenging when the stair treads of the stairway are borne by stringers. To provide a stairway that is stable over time, the stairway must also be anchored in a frost-free manner, which may make it necessary to replace mass. Depending on the size of the stairway, it may be of a weight that requires transportation to the installation site by means of a motorised vehicle, and handling by means of a motorised lifting equipment, which in some places may be difficult or illegal.

A stairway solution for use in terrain is known, which comprises stool-like elements wherein each element has a top portion with four legs, wherein two legs are shortened relative to the two other legs. The longest legs are arranged at a nose portion of the stool-like element. Each of these longer legs are provided with bores that extend perpendicular to the longitudinal axes of the legs. A rod is arranged to be inserted through two bores so that the rod in a usage position extends between the longest legs to provide a bearing for preventing the legs from pressing down into the terrain when the stairway solution is in use. Such a stool-like stairway is as such made up of individually disposed stair treads that are borne against a surface of the terrain.

There is therefore a need for a stairway that is arranged to be installable in a stable manner substantially without any intervention in the terrain, wherein the stairway is assembled in situ, and wherein the stairway's riser may easily be adapted to variations in the terrain. For a stairway with only one stair tread, the riser or risers may for example be the vertical distance between a terrain and the stair tread.

The purpose of the invention is to remedy or reduce at least one of the disadvantages of prior art, or at least provide a useful alternative to prior art.

The purpose is fulfilled by the features specified in the description below and the subsequent patent claims.

The invention is defined by the independent patent claims. The dependent claims define advantageous embodiments of the invention.

In a first aspect of the invention, a stairway for use in terrain is provided, wherein the stairway comprises at least one stair tread, wherein the at least one stair tread comprises a tread portion that is delimited by a nose portion, a rear portion opposite the nose portion, and two side portions. The at least one stair tread is in a position of use provided with clamping means arranged to receive and connect elongated bearing rods to the stair tread to bear the at least one stair tread at a distance above a base. The clamping means comprises separate clamping means, one for each bearing rod, wherein each clamping means is arranged to connect the stair tread to a bearing rod that is inserted through an opening in the tread portion.

The elongated bearing rods are preferably arranged to be guided towards or into a ground with their longitudinal axis substantially perpendicular to the plane of the tread portion.

Typically, the bearing rods will be guided against a ground when the ground is made up of a stable, solid base such as rock or another adequately solid ground of for example concrete. If the ground of a terrain is loose or not frost-proof, it would be advantageous if the bearing rods penetrate the ground for example down to solid ground or to frost-free ground. As such it would be advantageous if the bearing rods at installation are longer than the sum of the stairway's riser and distance to the surface of the ground.

In a preferred embodiment, each clamping means is arranged in connection to the side portions of the stair tread. As the clamping means is arranged to connect the bearing rods to the stair tread, a clamping means arranged in connection to the side portions of the stair tread will substantially not be a hindrance to a user if the bearing rods in a usage position rise above the tread portion of the stair tread. In some embodiments of the at least one stair tread of the stairway according to the invention, the side portions are better suited to be connected to the clamping means, as the strength of the side portions may be greater than that of the stair tread's nose portion and rear portion.

In one embodiment, the stairway may be made up of at least two stair treads so that the invention in such an embodiment is a stairway for use in terrain, wherein the stairway comprises at least two stair treads, wherein each stair tread comprises a tread portion that is delimited by a nose portion, a rear portion opposite the nose portion, and two side portions. Each of the at least two stair treads may in a position of use be provided with clamping means arranged to receive and connect elongated bearing rods to the stair tread to bear the at least two stair treads at a mutual distance above a base.

In an embodiment wherein the stairway is made up of at least two stair treads, it may be advantageous if at least the stair tread or stair treads arranged between the stairway's top and bottom stair treads are borne by at least four bearing rods, at least two of the at least four bearing rods being common for two subsequent stair treads. More than four bearing rods, for example six bearing rods, may be an option for a stair tread that makes up a landing slab, which is a horizontal plane in a flight, wherein the landing slab has a run that is longer than the remaining stair treads of the stairway.

In an embodiment of a stairway wherein at least the stair tread or stair treads arranged between the top and bottom stair treads of the stairway are borne by four bearing rods, the least number of bearing rods will be given by the formula:

S = (T x 2) - 2, wherein S is the number of bearing rods and T is the number of stair treads.

The formula above will also apply if a portion of the bottom stair tread and a portion of the top stair tread abut a foundation, for example a terrain or another foundation, or the bottom and top stair tread is borne by only two bearing rods.

In embodiments where also the top and the bottom stair tread are borne by four bearing rods, the least number of bearing rods will be given by the formula:

S= (T x 2) + 2.

By arranging the stairway so that, in an embodiment with two or more stair treads, at least two of the four bearing rods are common for two subsequent stair treads, each stair tread is connected to at least one adjacent stair tread. Even though the stairway according to the invention in an embodiment with at least two stair treads is without stringers, meaning stringer-free, experiments have shown that the stairway achieves a stability similar to that of a corresponding stairway that has treads fastened to stringers.

It is advantageous if each clamping means is adjustably arranged relative to the side portions of the stair tread. An adjustably arranged clamping means makes it possible to easily provide a turn in the stairway, meaning a non-linear flight. In one embodiment of the invention, the tread portion is of a grid type with square openings, each of the clamping means being arranged to connect the stair tread with a respective bearing rod disposed in any of the openings by the side portions of the stair tread.

In one embodiment, the clamping means comprises a clamp fitting with a through-going first bore arranged to receive a bearing rod, and a clamping bolt threadedly connected to a second bore, the clamping bolt being arranged to apply a clamping force against a bearing rod that is inserted into the first bore and connect the clamp fitting to a portion of the stair tread. This has the effect, among others, that the clamping means may be substan- tially "hidden" in a portion of the stair tread's tread portion. A substantially hidden clamping means will represent no or approximately only an insignificant hindrance to the surroundings.

Separate clamping means are of special interest when the clamping means is arranged in connection to an interior of the stair treads, and when the tread portion of the stair tread is of a grate or grid type with through-going, vertical openings. Said openings may then be used to delimit the movement of the clamping means in an X-Y direction, meaning in a plane parallel to the tread portion, and the clamping means is disposed in the desired one of said openings to provide for example a turn in the flight.

In a second aspect of the present invention, a method is provided for assembling a stairway according to the first aspect of the invention, wherein the method comprises the steps of:

A) disposing the at least one stair tread of the stairway at the desired location and disposing a bearing rod through the tread portion and in connection to at least the clamping means that is located nearest the nose portion or the rear portion of the stair tread on each of the side portions of the stair tread;

B) guiding the bearing rods to the desired position against or into the base; and

C) fixedly connecting the bearing rods to the respective clamping means.

In one embodiment, the method of step A) comprises disposing the bearing rods in connection to the clamping means by both the nose portion and the rear portion. Thereby, the entire at least one tread may be borne at a distance above the ground.

The method may further comprise assembling a stairway with more than one stair tread, and may then further comprise:

D) disposing a subsequent stair tread of the stairway, wherein the bearing rods from the first or the previous stair tread are connected by the clamping means to the subsequent stair tread, so that a bearing rod that extends from the first stair tread's clamping means disposed nearest the nose portion or the rear portion, is connected to this subsequent stair tread's clamping means which is disposed nearest the rear portion or the nose portion respectively, and wherein bearing rods are connected to the remaining two clamping means so that this subsequent stair tread is borne by four bearing rods in total;

E) repeating step D) until at least the second to last stair tread of the stairway is disposed; and

F) disposing the last stair tread of the stairway by guiding at least the clamping means of the last stair tread into connection with the bearing rods of the previous stair tread.

In one embodiment, the method comprises installing the stairway that comprises two or more stair treads in such a way that the first stair tread is the top stair tread of the stairway. The stairway may as such be installed "from the top down". Alternatively, the method may comprise installing the stairway so that the first stair tread is the bottom stair tread of the stairway. The stairway may as such be installed "from the bottom up". In a further alternative method, the stairway may be installed from the top down and from the bottom up simultaneously. This is possible due to the adjustability that the invention facilitates in the stringer-free stairway.

The method comprises in one embodiment guiding a portion of the bearing rods down into the ground when installing the stairway. When the bearing rods have been guided down into the ground to the desired depth, the clamping means may lock the bearing rods to the stair treads.

In the following, examples are described of preferred embodiments which are illustrated in the attached drawings, wherein:

Fig. 1a shows a vertical view in perspective of a stairway that is not part of the invention, wherein bearing rods are connected to clamping means arranged on an exterior of side portions of the stair treads;

Fig. 1b shows at a larger scale a detail of a clamping means shown in fig. 1 a;

Fig. 2a shows a vertical view in perspective of an embodiment of a portion of a stairway according to the invention, wherein bearing rods in the form of square tubulars are arranged through openings in each of the tread portions;

Fig. 2b shows the stairway in fig. 2a from above;

Fig. 3 shows a portion of a stairway according to the invention seen from above, wherein the stairway is arranged with a non-linear flight;

Fig. 4a shows at a larger scale a separate, isolated clamping means; and

Fig. 4b shows the clamping means in fig. 4a in a usage position, wherein the clamping means is arranged in an opening in a tread portion. All position indicators refer to the position shown in the figures.

The same or corresponding elements are indicated with the same reference number in the figures. For the sake of clarity some elements may not have reference numbers in some of the figures.

A person skilled in the art will understand that the figures are only principle drawings, wherein details that are not important for demonstrating what is new about the invention, may have been left out. The relative ratio between individual elements may also be distorted.

In the figures, the reference number 1 indicates a stairway according to the invention. The stairway 1 in the embodiment examples comprises more than one stair tread 3 and bearing rods 5 for bearing the stairway above a base U. The base U may be a terrain or a foundation in or outside a building.

Each stair tread 3 comprises a tread portion 31 that is delimited by a nose portion 33, a rear portion 35 opposite the nose portion 33, and two side portions 37.

In a usage position, each of the stair treads 3 are provided with a clamping means 7 that is arranged to receive and connect the bearing rods 5 for bearing the stair treads 3 at a mutual distance over the base U.

In the figures, the clamping means 7 is shown arranged in connection to the side portions 37 of the stair treads 3.

In the figures 1 a and 1b, which are not part of the present invention, the clamping means 7 is arranged to be able to be disposed on an exterior of the side portions 37 of the stair treads 3. The clamping means 7 shown in fig. 1a comprises a bearing plate 71 that is fixed to the side portion 37 by means of screws 73, and clamp fittings 75 that in the embodiment shown are fixed to the bearing plate 71 by means of a weld connection. The clamp fittings 75 project out from the side portion of the bearing plate 71 . Each of the two clamp fittings 75 shown is provided with a through-going first bore 76 that is arranged to be able to receive a bearing rod 5. Each clamp fitting 75 is further provided with a clamping bolt 77 that is threadedly connected to a second bore 78 that in the embodiment shown is substantially perpendicular to the first bore 76. The second bore 78 is in connection with the through-going first bore 76 so that the clamping bolt 77 may apply a clamping force against the bearing rod 5 to prevent relative movement between it and the clamp fittings 75, and thereby the stair tread 3. The stairway of fig. 1 a is shown disposed in an inclined terrain.

The clamp fitting 75 is shown at a larger scale in fig. 1 b.

Since the clamping means 7 shown in fig. 1 a is arranged in connection to the exterior side portions 37 of the stair treads 3, the clamping means 7 is independent of the design of the tread portion 31 . The tread portion 71 may as such be designed without through-going openings as shown in figures 1 a and 1 b, or with openings or friction-increasing perforations that will be known to a person skilled in the art. The stairway 1 according to the invention may as such be produced by means of stair treads 3 of a standard type that are commercially available.

The bearing rods 5 shown in fig. 1 a may for example be in the form of reinforcement rods produced for use as reinforcement in concrete constructions. Such reinforcement rods 5 are typically produced in standard lengths of six meters and are suitable to be driven down into a terrain in nearly their entire length or until they hit solid ground like for example rock. Adequate laying of foundation to frost-free depths may as such be achieved substantially without intervention in the terrain. The reinforcement rods 5 may easily be cut to the desired length, typically after an elevation of each of the stair treads 3 has been determined and the reinforcement rods 5 are clamped in the clamping means 7.

Figures 2a-3 show an embodiment of the stairway 1 according to the invention, wherein the stair treads 3 of the stairway 1 are provided with a tread portion 31 of a grid type with square openings 31 ' arranged between the nose portion 33, the rear portion 35 and the side portions 37. In the embodiment shown in fig. 3, the bearing rods 5 are in the form of square tubulars 5, wherein each square tubular 5 is inserted through a respective opening 31 ' that is delimited by the side portions 37. In the embodiment shown, the clamping means 7 is made up of screws 73 that are inserted through bores or holes in the side portions 37, and of a portion of the peripheral delimitation of the opening 31 '. In one embodiment, the screws 73 are arranged to apply a clamping force against a surface of the square tubulars 5. In such an embodiment, the bores in the side portions 37 are provided with threads adapted to the threads of the screws 73. In another embodiment, the screws 73 are arranged to penetrate at least one of the walls of the square tubular 5. This may for example be achieved by means of self-drilling screws, or by drilling a hole through the wall of the square tubular 5 before the screw 73 is guided through the bore in the side portion 37 of the stair tread 3 and thereafter through the hole or holes in the wall of the square tubular 5. Fig. 2a shows different embodiments of the clamping means 7 in the form of screws 73. The bearing rods 5 that connect the second lowest stair tread 3 to the adjacent tread 3 (the first and third stair tread 3 viewed from above) are provided with self-drilling screws 73. In the embodiment shown, each bearing rod 5 is fixed to each side portion 37 by means of two self-drilling screws 73 through adapted bores as shown.

Further, the pair of bearing rods 5 that extend through the third and fourth stair tread 3 are in the form of square rods with a solid cross-section that are fixed to said tread 3 by means of clamping means 7 in the form of screws 73 or clamping bolts that are threadedly connected to bores in the side portions 37. Correspondingly, the pair of bearing rods 5 for the top tread 3 is shown in an embodiment with solid rods with a substantially circular cross-section, and are fixed to said tread 3 by means of clamping means 7 in the form of screws 73 or clamping bolts that are threadedly connected to bores in the side portions 37. It should be emphasised that a stairway 1 according to the invention will normally have one common type of bearing rods 5.

One advantage of disposing the bearing rods 5 on an interior side of the side portion 37 of the stair tread 3, is among others that the clamping means 7 is substantially "hidden" and represents practically no hindrance to the surroundings.

In the embodiment shown in fig. 2a, the bearing rods 5 project above the stair treads 3 and are used as support for a hand rail 51 in addition to bearing each stair tread 3. In fig. 2b, which shows the stairway 1 from above, the bearing rods 5 are shown with dashed lines.

Figures 4a and 4b show a clamping means 7 for use on an interior side of the side portion 37 of the stair tread 3, and in connection with a bearing rod 5 with a cross-sectional shape that does not fit openings 31 ' in the tread portion 31 . The clamping means 7 shown in figures 4a and 4b, is a clamp fitting 75 that may be regarded as an "adapter" designed to be able to be guided into one of the openings 31 ' in the tread portion 31 , and simultaneously be able to receive a bearing rod 5, for example in the form of a rod with a circular crosssection as shown in fig. 4b. The clamp fitting 75 shown in figures 4a and 4b, has fundamentally the same function as the clamp fitting 75 shown in figures 1 a and 1 b, the clamp fitting 75 being provided with a through-going first bore 76 that is arranged to receive a bearing rod 5. The clamp fitting 75 is further provided with a clamping bolt 77 that is threadedly connected to a second bore 78 that in the embodiment shown is substantially perpendicular to the first bore 76. The second bore 78 is in connection with the through- going first bore 76 so that the clamping bolt 77 may apply a clamping force against the bearing rod 5 to prevent relative movement between it and the clamp fitting 75. As shown in fig. 4b, the clamping bolt 77 is inserted through a bore (shown with dashed lines) in the side portion 37 of the stair tread 3 and thereafter into the second bore 78 in the clamp fitting 75. The bearing rod 5 is thus fixed to the stair tread 3.

The clamp fitting 75 shown in figures 4a and 4b, is arranged to be arrangeable independently of the other clamp fitting(s) 75 for fixing bearing rods 5 to stair treads 3. Such an independent arrangement is especially useful if there is a wish or need for installing a stairway 1 that has a non-linear flight. An example of such a stairway 1 is shown in fig. 3, wherein the bearing rods 5 are square tubulars. By means of the clamp fitting 75 shown in figures 4a and 4b, such a non-linear flight may easily be produced in an embodiment with bearing rods 5 for example in the form of reinforcement rods or other bearing rods with a different cross-sectional shape than the shape of the openings 31 ' of the tread portion 31 or that in other ways do not fit the openings 31 '.

For stair treads produced of metal, side portions 37 are commonly produced with sturdier profiles than the nose portion 33 and rear portion 35 of the stair tread. It is therefore advantageous and preferred to dispose the clamping means 7 in connection to the side portion 37 of the stair tread. It should however be understood that the clamping means 7 alternatively may be disposed in connection to the nose portion 33 and in connection to the rear portion 35 in a linear flight.

Reference is again made to figures 2a and 3, wherein a portion of a stairway 1 according to the invention is assembled with five and four treads 3, respectively. Reference is also made to fig. 1a, which does not form part of the invention.

In fig. 1a, each of the bottom stair tread 3 (the tread to the right in the figure) and the top stair tread 3 is connected to four bearing rods 5, but wherein two of the bearing rods 5 are common for both stair treads 3 so that the common bearing rods 5 provide a connection between the two stair treads 3 shown. Experiments have shown that the common bearing rods 5 provide a very stable stairway 1 , even though the stairway 1 according to the invention is stringer-free.

In fig. 2a, each of the bottom stair tread 3 (the tread to the left in the figure) and the top stair tread 3 is connected to only two bearing rods 5 that in addition are common for the subsequent, respectively preceding stair tread 3. In fig. 3, an example is shown of a stairway 3 of the type that is shown in fig. 2a and 2b, but wherein the stairway 3 is assembled with a non-linear flight. The stair treads 3 are shown in principle. As shown, bearing rods 5 are arranged through those openings 31 ' in each stair tread that border the side portion 37 and the nose portion 33. By the right portion of the stairway 1 , the bearing rods 5 for the three top stair treads 3 extend through the openings 31 ' in each underlying stair tread 3, wherein the openings 31 ' in the underlying treads 3 border the side portion 37 and the rear portion 35. However, by the left portion of the stairway 1 , the bearing rods 5 for the three top stair treads 3 extend through the openings 31 ' in underlying stair treads, which border the side portion 37 and are midway between the nose portion 33 and the rear portion 35. By disposing the latter bearing rods 5 in other openings 31 ' than the middle one as shown in the embodiment in fig. 3, the curvature of the flight will change.

The embodiments shown in figures 2a and 3, may be with a corresponding number of bearing rods as shown in fig. 1 a, wherein each of the bottom stair tread 3 (the tread to the right on the figure) and the top stair tread 3 is connected to four bearing rods 5, but wherein two of the bearing rods 5 are common for both stair treads 3 so that the common bearing rods 5 provide a connection between the two stair treads 3 shown. Experiments have shown that the common bearing rods 5 provide a very stable stairway 1 , even though the stairway 1 according to the invention is stringer-free.

When using separate clamp fittings 75 as shown in fig. 4a and 4b, bearing rods 5 of the type shown in fig. 3 may be replaced by bearing rods 5 of the type shown in fig. 1 a to provide a stairway 1 as shown in fig. 3.

In one embodiment (not shown), the stairway according to the invention is designed so that each tread 3 is borne by only two bearing rods 5 that are connected to each their side portion 37 of the stair tread 3 by means of clamping means 7, 75. In such an embodiment, the clamping means are typically arranged by each their side portion 37 approximately midway between the nose portion 33 and rear portion 35 of the stair tread. The effect of an embodiment with only two bearing rods 5 for each stair tread 3 is that each stair tread 3 is independent of the other stair treads 3, and will consequently not achieve the same degree of rigidity as the embodiments shown in for example figures 1 a, 2a and 3.

Based on the description above, it should be understood that embodiments of the stairway 1 according to the invention, is a stairway without stringers, wherein the stairway is arranged to be installable in a stable manner substantially without interventions in for exam- pie a terrain. The stairway 1 may be assembled in situ, wherein the stairway 1 may easily be adapted to variations in the terrain with regards to inclination, risers, and any turns in the flight of the stairway, and wherein the bearing rods 5 of the stairway 1 may be guided to solid or frost-free ground substantially without intervention in the terrain. It should be noted that all embodiments mentioned above illustrate the invention, but do not delimit it, and persons skilled in the art will be able to design many alternative embodiments without deviating from the scope of the attached claims. In the claims, the reference numbers in parenthesis shall not be considered delimiting.

The use of the verb "to comprise" and its different forms does not exclude the presence of elements or steps not mentioned in the claims. The indefinite articles "a" or "an" before an element do not exclude the presence of more such elements.