Prefabricated staircase

Abstract: The standardized step module according to the present invention is provided with a pair of wings disposed aside of the step (50) and having the shape, as seen in a side section, of a parallelogram whose bases are parallel to the tread of the step (50) and are separated by a distance equal to the riser of the step (50). In the case of a step (50) made of reinforced concrete, said wings are constituted by a metallic structure having said parallelogram shape and provided with suitable reinforcing members and buried in a casting of concrete. According to the invention, the metallic structure forming the step wing is provided with suitable coupling means for joining it to other adjacent modules, said means being generally constituted by through-holes into which are inserted, for instance, fixing bolts and nuts. The conformation of the structure forming a wing of the module according to the invention allows a high production at a low cost of such reinforced concrete modules to be achieved.

Description: The present invention relates to a prefabricated staircase for civil and/or industrial buildings, comprising a plurality of steps, each of said steps comprising a riser element, a tread element and a pair of side elements, and at least one side structure suitable for supporting said steps. The invention may be mainly applied in the field of industrialized building technique. The use of prefabricated staircases in building technique is widely known. By way of example, a known staircase is provided with single step elements having, each, a pair of supporting side elements, a riser and a tread, said step elements being able to be joined with other similar elements in order to form a staircase having a rectilinear or a helical development. In order to allow a pair of adjacent elements to be joined together, each of the side elements which are disposed aside of the step has a so-called "chair-like" conformation (see fig. 1), which may be geometrically defined, in a side section, as a partial overlapping of a pair of rectangles, the respective bases of which are parallel to each other. Thus, each side element has a pair of recesses into which similar side elements belonging to adjacent steps are respectively inserted. Furthermore, the periphery of each side element is provided with several grooves, in which reinforcing rods are buried, said rods extending through the whole length of the staircase and acting as a supporting structure and as a holder for mantaining in a given position the structure which is formed by the joined steps. The laying operation of a staircase having steps of the type mentioned above firstly begins by fixing to the floor the first step, in such a way as to form a base for the whole staircase. Thereafter, the riser of the following step is placed upon the preceding step; each step is provided with a (generally wooden) falsework which is placed on the floor. Once the whole staircase is assembled, with the exception of the last step, which acts as a footpace, suitable iron rods are inserted into the lateral grooves which are provided along the side elements of each step; then, the last step is positioned and the iron rods are blocked into their seats, by means of anchoring them to the upper floor and of burying them in mortar of cement within said grooves. The supporting falsework is then removed. Both of the monolithic step described above and the process for laying a staircase provided with such steps involve a plurality of disadvantages and drawbacks. Concerning the process for laying the staircase, a major drawback is due to the fact of needing, for each single step, a supporting falsework or cribbing, whose height should be adapted to the step distance from the floor; this involves a great loss of time for laying the cribbing, remarkable costs for the cribbing itself and, finally, (and this fact particularly applies in the case of laying helical stairs), the area located under the staircase may not be accessed to, owing to the presence of the struts which form the cribbing. Finally, laying and burying a series of iron rods into the grooves involve futher losses of time and work. Concerning the monolithic step per se, the process for casting each step is extremely disadvantageous, both from the economical and from the productivity points of view. In fact, casting such steps implies the use of special forms such as, for instance, the forms which are described in italian patent n. 1.175.179, which have an extremely complicated structure constituted by several portions which are interconnected, for instance, by means of pivots, bolts and nuts and tension rods, said forms being provided with several surfaces for delimiting each step, said surfaces being disposed on plans which intersect themselves with different angles. These kinds of forms, which are normally used for casting steps of precast staircases are, owing to their complicated structure, very expensive and they have to be frequently replaced, thereby causing a strong increase of the staircase production costs. Furthermore, the daily production of these kinds of step is rather limited since, prior to casting the concrete into the form, the latter should be provided in its interior with various metallic nets or grids for reinforcing, respectively, the side elements and the tread of the step. Finally, once the step is ready for receiving the casting of concrete, it should be placed in a vertical position, a side element being placed on the floor. This arrangement provides for other disadvantages, since the opening for casting the concrete is rather small, and since the form may not be placed into a perfectly stable position. The latter drawback is amplified in the case of casting of steps for helical staircases, whose forms, owing to casting reasons, should be placed with the smaller base placed on the working plan; thus, in order to avoid the form to be overturned, it should be adequately supported from outside. Document CH-A-531.628 discloses a staircase forming metallic element comprising two parallel side flanges connected by two transversal walls which lay on planes at right angles relative to said flanges. Said transversal walls, which respectively constitute the tread and the riser of the step, comprise respective male/female joints for the connection to other similar elements. Such a staircase does not have any flexibility of use, owing to the stiffness of the connections between the different elements. In particular, the dimensions of the tread and of the riser of the steps may not freely be modified. Therefore, the staircase may only be used for connecting floors which are located at precisely predetermined distances from each other. Furthermore, due to its metallic monolithic structure, the step is not suitable for being covered by means of high-quality materials such as wood, marble etc.; a staircase built according to the teachings of said swiss document, thus, may only be seen as a low cost emergency solution; it will never be used in valuable rooms or buildings. Document FR-A-761.621 discloses a metallic staircase constituted by plate elements which are folded in order to form the steps of the staircase; said elements may be restrained into each other. Document FR-A-2.065.332 discloses a prefabricated staircase according to the preamble of claim 1 of the present application. Finally, document DE-B-1.042.868 discloses a self supporting staircase which is constituted by a plurality of step modules and provided by supporting tension bars. The present invention aims to obviate the disadvantages and drawbacks which are typical of the background art, and to provide, thus, for a prefabricated staircase, which is formed by a plurality of standardized step modules, said staircase being able to be assembled rapidly and at a low cost and which would allow an operator to access the area underlying the staircase during the assemblying operations. This is achieved by means of a staircase having the features disclosed in claim 1. The dependent claims describe advantageous forms of embodiment of a staircase according to the invention. The standardized step module belonging to the staircase according to the present invention is provided with a pair of side elements disposed aside of the step and having the shape, as seen in a side section, of a parallelogram whose bases are parallel to the tread of the step and are separated by a distance equal to the riser of the step. According to the invention, the metallic structure forming a side element is provided with suitable coupling means for joining it to other adjacent modules, said means being generally constituted by through-holes into which are inserted, for instance, fixing bolts and nuts. Still, the conformation of the module enables a quick and comfortable assemblying of a staircase provided with such modules. In fact, the assemblying operation takes place just laying the lower base of the side element of a step upon the the upper base of the preceding step, then rigidly fastening together the two modules and repeating this procedure until the whole staircase is assembled. Such an assemblying process allows a series of important advantages to be achieved in respect of the prior art technique: in fact, during the assemblying operation, the staircase according to the invention needs a single, central, supporting strut, instead of a whole cribbing or falsework underlying the staircase, this implying a remarkable save of time and of material for the supporting falsework. Furthermore, the staircase according to the invention does not require any laying operation of lateral reinforcing and supporting rods, nor a subsequent operation of burying said rods in a concrete casting: once the staircase according to the invention is assembled, it may immediately be trimmed, and this implies a remarkable save of time in respect of the prior art technique. According to a feature of the invention, each module comprises a metallic structure formed by two parallel horizontal sides connected by two inclined sides, such structure being substantially parallelogram-shaped and further comprising a reinforcing element disposed between the vertices of said parallelogram. According to the invention, the parallel horizontal sides are provided with coupling means which, in operation, cooperate with means for fastening a step, which step includes connecting means suitable for cooperating with said coupling means, said step being formed by a composite structure which may be made either of concrete/metal or only of metal, wood or other materials. According to an advantageous form of embodiment of the invention, the means for coupling pairs of adiacent and superimposed steps may also be used for fixing a series of accessories, such as for instance metallic uprights for supporting a breastwwork or a bannister handrail. Other features and advantages of the invention will become apparent from reading the following description, of a form of embodiment of the invention, given as a non-limiting example, with the help of the drawings shown in the attached sheets, in which: figure 1 shows a schematical perspective view of a type of staircase known in the art; figure 2 shows a side view of a module of a supporting structure of a staircase according to the invention; figure 3 shows a partial side view of a staircase comprising a plurality of modules according to fig. 2; figure 4 shows a schematical perspective view of a staircase according to fig. 3, and figure 5 shows a side view of another form of embodiment of the invention. In figure 1, a precast staircase 10 in reinforced concrete, of a type known in the art, is constituted by a plurality of superimposed steps 11', 11" ..., each of said steps comprising a riser, a tread and a pair of side portions 12, 12' which are respectively disposed at each side of the step. As previously mentioned, each side element 12, 12' has a "chair-like" conformation, delimiting a pair of recesses suitable for receiving the extensions belonging to an adjacent side portion. Supporting and reinforcing iron rods 13, 13' ... are inserted in suitable grooves and buried in a casting of concrete. This known form of embodiment has the mentioned disadvantages, which are mainly relative to the production of the single steps, owing to the difficulty of providing for suitable forms, which always have a very complicated conformation and, therefore, a high cost. Furthermore, it is not possible to provide for standardized connectors for fixing supporting uprights of a handrail; such uprights should necessarily be cemented in suitable holes which are bored on the step side portions once the whole staircase is completely assembled, thereby causing further losses of time and work for providing said holes. Figures 2 to 4 show the staircase according to the invention. Staircase 30 comprises at least one reticular supporting structure constituted by a plurality of modules 31 (see fig. 2) superimposed to each other, each of these modules comprising a pair of horizontal bars 32, 33 which are connected by their ends to a double-bent bar 34. The module according to this form of embodiment has the shape of a parallelogram, whose bases are constituted by horizontal bars 32, 33, while the inclined sides 34 1 , 34 2 are constituted by the two end tracts of bar 34; the central tract 34 3 of bar 34 forms in this case a reinforcing element for each module 31 of the structure. The respective ends of said bars 32, 33, 34, as well as the two areas where bar 34 is bent in order to form the reinforcing element 34 3 , are provided with through-holes which enable the passage of screw means 35, 36, 37, 38 (see figures 3 and 4) suitable for rigidly coupling to each other the respective elements consituting each module 31 and pairs of adjacent modules. Such a reticular supporting structure is characterised by a constant distance between the axes of the respective holes 35, 36, 37, 38 and then, once the staircase is assembled, by constant tread widths. On the other hand, in the vertical direction, each module 31 may be separated from an adjacent module by means of suitable washers 39, 40, 41, 42, by means of which different inclinations for the forming staircase flight, and thus step risers of different heights, may be achieved. According to the invention, each horizontal bar 32, 33 of each module 31 is provided with a pair of through holes 43, 44, 45, 46 located at regular intervals from the ends of said bar 32, 33, in such a way that respective hole pairs are aligned to each other when a module is placed upon another one. Said through-holes 43-46 are suitable for enabling the passage of screw means for fastening a step having the following structure. A step 30 is constituted, according to the form of embodiment shown in the figures, by a pair of metallic side elements 51, 52 which outline the shape, in side view, of the step itself; therefore, these elements comprise a riser and a tread. According to this form of embodiment, each of the side elements 51, 52 is provided with a pair of brackets 53, 54 which are disposed at right angles relative to elements 51, 52 and which comprise through-holes enabling the passage of said screw means 47, 48. A step of this kind is realised by means of the following procedure: a pair of metallic side elements 51, 52 is rigidly coupled by means of some (generally three) metallic bars which are welded between the walls of said side elments 51, 52; a wooden form, having a shape corresponding to that of elements 51, 52, is placed between said elements 51, 52; possible additional sections, e.g. a section for supporting an anti-skid device placed between the riser and the tread of the step, and/or a section outlining an intersection area for a plate (for instance a wooden, marble or granite plate) dignifying the step 50, and/or a section for supporting a rubber element placed at the end of the tread in order to facilitate cleaning of the step 50, are placed between said elements 51, 52; light concrete is cast inside of the form. Once the casting is solidified, the step 50 is ready for being assembled on structure 31. In fact, the bored brackets 53, 54 are simply placed in correspondence of the holes 43, 44 which are present on horizontal bars 32, 33 of structure 31 and the assembly is fastened by screw means 47, 48. The staircase 30 according to the invention may be assembled by means of a procedure enabling a great working practicalness for the operators. In fact, since the trellis structure 31 forming the support for the steps 50 is self-supporting, the staircase 30 is built up according to the following procedure: the first structure element 31 is fastened to the floor, possibly by blocking it against a starting footpace; a second structure element 31 is placed upon the first one and it is immediately fastened to said first element by means of screw means, e.g. 35 and 37; similarly, further structure elements 31 are superimposed to the first ones until the upper floor is reached; the last elements may be placed on the upper floor in order to constitute a footpace; in the case of double-flight staircases, an intermediate footpace may be realised by means of suitably shaped structure elements. According to this form of embodiment of the invention, the staircase 30 comprises a pair of supporting structures formed by elements 31, said structures being parallel to each other, the step being placed between them. In order to facilitate assemblying of the staircase supporting structure, suitable "working treads" (not illustrated in the figures) may be placed between the two supporting structures while elements 31 are being superimposed to each other. Such "working treads" are simply constituted by rectangular shaped metallic elements which are fixed between the structures by using the holes 43-46 which are present for the ultimate fastening of the steps. These "working treads" perform a first task of spacer between the two supporting structures parallel to each other; furthermore, they allow the operators to climb the staircase during the assemblying operations of the latter, and thus to quickly reach the upper portions of the staircase itself. Using these "working treads", therefore, implies the substantial advantage of firstly assemblying the whole staircase supporting structure, and then placing and fastening the steps 50. In this way steps 50 may not be damaged during the assemblying operations. As it may be noted in figures 3 and 4, a horizontal bar of a structure module 31 comprises a vertical prolongation 57. This prolongation 57 is advantageously used for constituting an upright for supporting a breastwork and/or a bannister handrail and, since the staircase has a modular structure, a plurality of uprights may be disposed along the staircase, at regular and strictly equal intervals. The staircase 30 described above is provided with a pair of modular supporting side structures. However, the invention may also be carried out by means of a single supporting side structure, in the case where each step 50 is fastened by one side to said structure, and by the other side is directly fastened to a wall. Figure 5 shows another form of embodiment of the invention. In this case the lateral supporting structure 60 comprises a pair of rectilinear metallic bars 61, 62 parallel to each other. Metallic reinforcing elements 63 are interposed between said bars 61, 62 at regular intervals, said reinforcing elements 63 including a first portion 64, suitable for supporting the tread forming element of the step, and a second portion 65 which is generally disposed at right angles relative to said bars 61, 62. Suitable screw means 66 realise the mechanichal coupling between the respective bars 61, 62, 63. The structure according to this form of embodiment features a more limited flexibility of use in respect of those structures which have been described with reference to figures 1 to 4, since the tread and the riser of the step are, in this case, placed at strictly fixed and predetermined distances. It is possible to modify the dimensions of these parameters by increasing the length of portion 65 of element 63, i.e. by increasing the distance between bars 51, 62. In this case both the height of the riser and the width of the tread are simultaneously increased. The solution illustrated in fig. 5 is anyway characterised by a great lightness, and allows large quantities of iron for the lateral supporting structures of the staircase to be saved. The invention has been previously described with reference to some preferred forms of embodiment. However, the invention comprises several further forms of embodiment which fall within its scope. According to a first variant of the invention, the connections between the different modules of the supporting structure are not carried out by screwing means, rather by welding. In this case the assemblying procedure of the staircase is carried out in a workshop, and the supporting structure are delivered to the yard in an assembled fashion. In the case where the steps are made of wood or of metal, said steps being constituted by a substantially rectangular plate, they may be directly fixed to the horizontal bars, without using any assemblying brackets or flanges, for instance by means of bolts and nuts cooperating with the holes which are present in the horizontal bars. According to a further variant, which is immediately derivable by examining figure 2, each parallelogram-shaped module 31 is constituted by a first bar forming a horizontal side and by an inclined side (e.g. by a single bar which includes sides 34 1 and 3 2 of the parallelogram), by a second bar forming another horizontal side and another inclined side (e.g. by a single bar which includes sides 34 2 and 33 of the parallelogram), and by a third reinforcing bar which corresponds to tract 34 3 of the bar 34 illustrated in fig. 2. According to another form of embodiment, at least one of the staircase supporting structures is assembled, in operation, on horizontal guides and is provided with means for anchoring it to said guides. In the case where the staircase has to be placed adjacent to a wall, this configuration enables the supporting structure close to the wall (or the whole staircase) to be displaced in order to facilitate the finishing works, such as the wall plastering works. In this case the staircase is delivered with "working treads" of a reduced length which are adaptable to the staircase reduced width when one of the supporting structures is brought near to the other one. The invention further comprises forms of embodiment according to which the staircase has a helical development. According to this form of embodiment, the metallic structures forming the reinforcing elements of the side portions are suitably pressed in order to obtain, when seen from above, the circular sector shape which is required by the project, while the substantially parallelogram shape of the side section of at least one of these structures is kept unchanged.

Claims: Prefabricated staircase (20) for civil and/or industrial buildings, comprising a plurality of steps, each of said steps comprising a riser element, a tread element and a pair of side elements, and at least one side structure suitable for supporting said steps, characterised in that said at least one structure is constituted by a plurality of superimposed parallelogram-shaped modules (31), each of said modules comprising two substantially horizontal bars which are rigidly coupled at each end thereof to two side bars (34 1 , 34 2 ), a reinforcing element (34 3 ) interconnecting two opposite corners of said parallelogram, further comprising first and second means (39, 41) for coupling together said substantially horizontal bars of two adjacent modules, and third means (53, 54) for rigidly connecting said steps to said side structure, said third means being independent of and placed between said first and second coupling means (39, 41). Staircase according to claim 1, characterised in that the inclined sides (34 1 , 34 2 ) of the parallelogram and the reinforcing element (34 3 ) are constituted by a single, suitably bent, metallic bar (34), and in that the horizontal (32, 33) sides are constituted by rectilinear bars. Staircase according to claim 1, characterised in that each module (31) comprises three bars, of which a first, suitably bended, bar constitutes one inclined side (34 1 ) and a horizontal (32) or vertical side of the parallelogram, a second, suitably bended, bar constitutes the other inclined side (34 2 ) and the other horizontal (33) or vertical side of the parallelogram, and the third bar constitutes the reinforcing element (34 3 ). Staircase according to claim 1, characterised in that said lateral supporting structure comprises a pair of inclined bars (61, 62) parallel to each other and having a length equal to the length of the whole staircase, and in that the reinforcing element (63) comprises a first portion (65) disposed substantially at right angles relative to said bars (61, 62) and a second portion (64) which is disposed, in operation, substantially horizontal and which is suitable for supporting a step element. Staircase according to anyone of claims 1 to 4, characterised in that said mechanical anchoring means (35-38) connecting the ends of adiacent modules (31) are constituted by screw means (35-38) or by weldings. Staircase according to anyone of claims 1 to 5, characterised in that spacers (39-42) are interposed between pairs of adjacent and superimposed modules (31). Staircase according to anyone of the preceding claims, characterised in that at least one of the substantially horizontal bars (32, 33) is provided with a substantially vertical extension (57) forming an upright for supporting a breastwork or a bannister handrail. Staircase according to anyone of the preceding claims, characterised in that each of said monolithic steps (50) comprises at least one metallic side element (51, 52) having a shape corresponding to that of the step, when seen in side view, said metallic side element being integral to said connecting means (53, 54). Staircase according to claim 8, characterised in that said connecting means (53, 54) are constituted by metallic flanges integral to said side elements. Staircase according to claim 8, characterised in that said metallic side elements (51, 52) are connected to each other by means of metallic bars buried in a concrete casting. Staircase according to anyone of claims 9 and 10, characterised in that each step (50) comprises an anti skid device placed between the riser and the tread of the step itself, and/or a covering made of a material dignifying the step, e.g. marble, granite or wood, and/or a section made of a resilient material placed at one end of the tread in order to facilitate cleaning operations. Staircase according to anyone of the preceding claims, characterised in that said at least one side supporting structure is suitable for forming main and/or intermediate footpaces. Staircase according to anyone of the preceding claims, characterised in that said step is constituted by a plate made of metal, wood or other material and in that it is directly fastened to one module (31) of supporting structure. Staircase according to anyone of the preceding claims, characterised in that it is realised in metal.

Inventors: MASTELLA MASSIMO, SALVA DOMENICO, MASTELLA, MASSIMO, SALVA', DOMENICO
Applicants: GENERALI COSTRUZIONI SRL, GENERALI COSTRUZIONI SRL ABBR. GECO SRL
Application year: 1992
Main classification: E04F11
IPC codes: E04F11