Modular step unit for prefabricated self-supporting ladders

Abstract: A modular step unit for self-supporting metal ladders comprises a pair of side supporting or bearing constructions (3, 3', 3'') supporting a flat ladder step (4, 4'). Connecting means (9) connect each modular unit to an adjoining modular unit for defining a self-supporting ladder ramp (1). Each supporting construction (3, 3', 3'') comprises at least a substantially vertical inner element (5) arranged between and rigidly coupled to at least a pair of substantially horizontal outer elements (6). The inner element (5) can be coupled to at least a pair of outer elements (6) including in an adjoining modular unit (3) by a coupling device (15) the height of which can be adjusted to provide a variable height or rise ladder ramp.

Description: BACKGROUND OF THE INVENTION The present invention relates to a prefabricated structure for outward and inward environment and, more specifically, it relates to a modular step unit for making modular ladders. A modular step unit according to the preamble of claim 1 is described in EP-A-0 128 880. Prefabricated ladders are provided for use in public and private environments, and they can be of a right plan type, a curved, ellipsoidal, ovoidal and mixed plan type. A lot of prior self-supporting ladders comprise a plurality of prefabricated metal elements of different shapes which are assembled to one another partially in an assembling shop, partially on the installing field, by removable coupling or connecting elements, such as screws, bolts, to allow them to be easily shipped and assembled-disassembled in very short times. Such a construction also allows to reduce to a minimum the number of standardized components, thereby also reducing the managing and storing costs for the makers thereof. Several examples of the above mentioned prefabricated or pre-made ladders are disclosed in the CH Patent No. 554,998, Belgian Patent No. 872,495, as well as in the German Patent Application No. 3,505,688 and French Patents Nos. 893,503, 604,662, 2,065,332, 2,597,909, GB Patent No. 151,487, U.S. Patent No. 4,355,700, European Patent No. 0,060,014 and Italian Patent Application No. MI96A 000410. A drawback of prior commercially available prefabricated ladders is that said ladders are excessively resilient because they are formed by individual metal sheet elements which are mutually coupled by coupling screws or nails. Thus, these prior constructions would be subjected to excessive oscillations and vibrations making said construction unstable and unsafe, and, accordingly, uncomfortable in use. Moreover, the mentioned highly resilient nature would reduce the structural strength thereof, with the requirement of adding stabilizing middle elements. A further drawback of prior prefabricated ladder constructions is that in these prior ladders it is not possible to precisely adjust the rise or height of the ladder steps, and, accordingly, of the overall step, mainly on the installing field and, for providing such a fine adjustment, prior ladder constructions usually comprise a lot of specially designed additional elements with a consequent increasing of the assembling time and cost. Yet another drawback of prior ladder constructions is that their component elements have an outer contour which is rather complex, said elements being frequently made by laser cutting sheet metal members. Yet a further drawback of prior ladder constructions is that they have a comparatively intricate configuration, with a lot of gaps and exposed to view connecting screw elements. SUMMARY OF THE INVENTION Accordingly, the aim of the present invention is to overcome or at least alleviate the above mentioned drawbacks, by providing a modular step unit and a prefabricated ladder construction having a highly rigid structure, and which can be simply and quickly assembled and installed, while providing a very good aesthetic aspect. Within the scope of the above mentioned aim, a main object of the present invention is to provide such a step modular allowing to reduce the oscillations and vibrations affecting prior ladder constructions, while enlarging the net distance of the ladder bearing elements, and eliminating the requirements of providing middle supporting elements. Yet another object of the present invention is to provide a modular step unit allowing to easily and quickly adjust the heights of the individual ladder steps. Yet another object of the present invention is to provide a modular step unit which is very simple construction-wise. According to one aspect of the present invention, the above mentioned aim and objects, as well as yet other objects, which will become more apparent hereinafter, are achieved by a modular step unit as defined in claim 1. The modular step unit according to the invention is specifically designed for self-supporting metal ladders, comprising a pair of side supporting constructions, which support a flat step element. Connecting means are moreover provided for connecting each unit to an adjoining unit in order to define a self-supporting ladder ramp, each supporting construction comprising at least a substantially vertical inner element arranged between and rigidly coupled to at least a pair of outer substantially horizontal elements; at least an inner element being adapted to be coupled to at least a pair of outer elements pertaining to an adjoining modular unit by a height adjustable coupling device in order to provide a variable height ladder ramp. BRIEF DESCRIPTION OF THE DRAWINGS Further characteristics and advantages of the invention will become more apparent hereinafter from the following detailed disclosure of some preferred, though not exclusive, embodiments of a step unit and a prefabricated ladder construction, which will be disclosed as a merely indicative and not limitative example with reference to the accompanying drawings, where: Figure 1 is a perspective view of a modular step unit according to the present invention; Figure 2 is a further perspective view illustrating a portion of a straight self-supporting ladder construction formed by a plurality of modular step units; Figure 3 is a side view illustrating a ladder construction of the type shown in Figure 1; Figure 4 is a further side view illustrating a variation of the ladder of Figure 3 provided with a parapet or guard element; Figure 5 is a further side view, on an enlarged scale, illustrating a detail of the ladder construction shown in Figure 4; Figure 6 is a perspective view of a sub-assembly of the modular step unit shown in Figure 1; Figure 7 is a further perspective view of another sub-assembly of the modular step unit shown in Figure 1; Figure 8 is a front view illustrating a modular step unit according to the present invention, as partially cross-sectioned according to a vertical plane; Figure 9 is a schematic side view illustrating a step unit according to the invention, with a component of the first size; Figure 10 is a view analogous to Figure 9 illustrating the same component of a second size; Figure 11 is a view analogous to Figure 10 illustrating the same component of a third size; Figure 12 is a perspective view of a detail of an adjustable connecting or coupling device included in the modular unit of Figure 1; Figure 13 illustrates a front view of the detail of Figure 12; Figure 14 is a cross-sectional view illustrating the detail of Figure 11, as cross-sectioned according to the section plane XIV-XIV; Figure 15 is a perspective view illustrating a further detail of an adjustable coupling or connecting device of the modular unit shown in Figure 1, in a first operating position thereof; Figure 16 is a front view illustrating the detail of Figure 15; Figure 17 illustrates a cross-sectional view of the detail of Figure 13 substantially taken along the section plane XVII-XVII; Figure 18 illustrates a cross-sectional view, on an enlarged scale, of a detail of the adjustable coupling or connecting device of the preceding figures, as cross-sectioned according to a vertical plane; Figure 19 illustrates a perspective view of the detail of Figure 15, according to a different use embodiment; Figure 20 illustrates a further perspective view of a modified embodiment of a modular step unit for a helical ladder construction, as seen from the inside; Figure 21 illustrates a further perspective view of the unit shown in Figure 20, as seen from the outside; Figure 22 illustrates a further perspective view of a helical or coil ladder construction made by assembling a plurality of modular units shown in Figures 20 and 21 as seen from the inside; Figure 23 illustrates a perspective view of the ladder construction of Figure 22, as seen from the outside; Figure 24 illustrates a side view of a ladder step, according to the present invention, including a specifically designed insert, for allowing the height of the ladder step to be vertically adjusted; Figure 25 is a front view illustrating a vertical modular unit; Figure 26 is a side cross-sectioned view illustrating the same vertical modular unit as shown in Figure 25; Figure 27 illustrates an enlarged detail of the vertical modular unit, in which inserts for adjusting the height of the step can be engaged; Figures 28 and 29 are respectively a front view and a cross-sectioned side view illustrating the mentioned inserts for adjusting the height of the ladder steps; Figure 30 is a side perspective view illustrating a step modular unit; Figure 31 is a schematic side view illustrating a ladder step, with a component of a first size, and provided with an insert including a middle hole for allowing a middle height adjusting of a ladder step; Figure 32 illustrates an enlarged detail of a vertical modular unit and of an insert provided with a middle hole; Figure 33 illustrates an insert provided with a middle hole; Figure 34 is a cross-sectioned and orthogonal side view illustrating the same insert as shown in Figure 33; Figures 35 and 36 are respective side views illustrating a ladder step including a recess for housing therein an insert for adjusting the height of the ladder step and being provided with an anchoring downwardly directed hole; and Figures 37 and 38 are respectively a cross-sectioned front and side view illustrating the mentioned insert provided with said downward directed hole. DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the above mentioned figures, a self-supporting ladder construction according to the present invention, which has been generally indicated by the reference number 1, comprises a plurality of modular step units, each indicated by the reference number 2, which are mutually coupled so as to provide a continuous type of construction. Each modular unit 2 comprises a pair of side supporting or bearing structures, indicated by the reference number 3, which, at the end portions thereof support a respective flat ladder step 4, possibly through one or more cross-members 4a. According to the invention, each side supporting structure 3 is a "sandwich" type of structure, including adjoining elements, and comprising at least an inner element 5, which substantially vertically extends between a pair of substantially horizontally extending outer element pair 6. Preferably, the inner elements 5 are provided in a number of two and are arranged between the pair of outer elements 6. The elements 5, 6 are constituted by essentially flat plates, formed from alloy steel (38NCD4) or stainless steel (AISI 316), having a thickness from about 8 to 12 mm, which have been automatically cut, for example by using a laser cutting apparatus. Both the inner elements 5 and outer elements 6 have a very simple elongated plan configuration, for example of approximatively rectangular shape, thereby allowing very quick and precise cutting operations to be performed. In this connection it should be also apparent that the cut elements could be also subjected to a plurality of surface finishing treatments, for providing said elements with a desired aesthetic final aspect. Advantageously, each outer element 6 is provided with a cross lug 7 extending from a longitudinal end portion of a major side thereof, and facing downwardly, as the element is in a full assembled condition. The inner elements 5 and outer elements 6 of each structure 3 are rigidly coupled by fixed coupling or connecting elements arranged at adjoining end portions thereof, thereby their middle axes extend in substantially perpendicular directions and their extension planes being substantially vertical. To that end, the inner elements 5 are provided with a pair of terminal circular holes 8, cooperating with corresponding circular holes 9 of like diameters, formed at an end of the outer elements 6. Preferably, the centers of the holes 8, 9 are arranged on a segment which is slanted at about 45° with respect to the middle axes of the elements 5, 6. The fixed coupling elements 10 each comprise a cylindric pin 11, having a diameter slightly less than that of the holes 8, provided with end threads, on which cylindric or tapering head clamping screws 12, 13 are engaged, said clamping screws being provided with respective flat face. Advantageously, the outer elements 6 are provided with counter-shaped cylindric or tapering seats or recesses for housing therein, in a not to the view exposed manner, the corresponding heads or screws 12, 13, thereby their flat outer faces are flush with the outer surfaces of the elements 6, to provide a continuous visual aspect and overcoming any gaps as due to possible projecting screws. Moreover, an anchoring bracket 15 for anchoring each cross-member 4a could be affixed to a face of the outer elements 6 adjoining the ladder step 4. Finally, between the two inner elements 5, and between each of said inner element and an adjoining outer element 6, spacing washers 14 provided for holding the several assembled elements at a set mutual distance. This distance, together with the several adjoining elements, will operate to increase the inertial momentum of the assembled construction 3, thereby providing the overall unit a high constructional stiffness. This high constructional stiffness will provide the unit 2 and assembled ladder construction with a very great resistance to oscillations and vibrations, much greater than in prior ladder constructions, thereby providing a ladder construction which can be comfortably used. Moreover, it would allow to make ladder constructions having a greater net distance between the ladder bearing or supporting elements, and will allow to overcome the requirements of using middle supporting elements in order to spatially support the ladder construction. According to the present invention, at least one of and preferably both the inner elements 5 are coupled to a pair of outer elements 6 pertaining to a modular unit 2', 2", 2"' ....2 n , by a coupling device which can be height adjusted in order to provide a variable height or rise ladder ramp. To that end, between each supporting structure 3 and an adjoining supporting structure 3', 3", 3"' ...3 n a lot of height adjustable coupling devices, generally indicated by the reference number 16, have been provided, in order to change the rise or height of the modular unit 2 and, accordingly, of the overall ladder construction 1. More specifically, said adjustable coupling or connecting devices, which have been generally indicated by the reference number 15, comprise a support element or insert 17, made starting from a cylindric washer provided with milled portions or parallel flat faces 18. Along the end circular edges thereof, the insert 17 is provided with steps 19 defining coupling contours. The insert 17 is provided with a vertical symmetry plane V and a horizontal symmetry plane C, with a central axis A. In the insert 17 a slotted hole 20 extending along the direction of the plane V is formed, said slotted hole having a diameter slightly greater than the outer diameter of the pins 11. Moreover, on the opposite faces of the insert 17 a plurality of tooth arrangements 21 are provided, including symmetrical and parallel teeth, which are symmetrically arranged with respect to the symmetry plane C. Owing to the disclosed arrangement, the opposite faces of the insert 16 can be precisely or snugly housed in two corresponding cavities 22 having a complementary configuration formed at the bottom end portion of two adjoining elements 5, which cannot turn about the axis A, owing to the provision of the two side milled portions 18. Each insert 17 will be coupled to a small plate 23 arranged between each inner element 5 and an adjoining outer element 6. More specifically, each plate 23 has a plan shape similar to that of the insert 17 and is provided with a central hole 24, having a hole axis B, and a tooth arrangement 25 similar to that provided on the insert 17, at a region thereof offset from the axis B. By arranging the plates 23 at a position facing the insert 17, and engaging pin coupling elements in the holes 20 and 24, the tooth arrangements 19, 25 can be mutually engaged thereby locking said arrangements after having set their height mutual positions. Owing to the symmetrical location of the tooth arrangements 21 on the insert 17 and the eccentric or offset location of the tooth arrangements 25 on the plates 24, the mutual position of this components can be displaced, with a maximum degree, either upwardly or downwardly, by turning through 180° the plate 23 about its turning axis B. Advantageously, it would be possible to provide standardized outer elements 6 including a plurality of lugs 7 having a different cross extension, corresponding to different rise adjusting ranges. As is schematically shown in Figures 9 to 11, the elements 6', 6", 6''' would be provided with respective lugs 7', 7", 7''' having different heights D', D", D"', in order to provide different height adjusting ranges. Moreover, on one of the outer elements 6 of each structure it would be possible to support suitable supporting elements for corresponding uprights 26 of a parapet or guard rail 27. In order to provide a curved, elliptical or helical ladder constructions, as indicated by 1c in Figures 22, 23, it should be necessary to use modular step units 2c which, though conceptually similar to the preceding modular units, would be constituted by inner 3i and outer 3e bearing structures of different configuration and length, supporting at the end portions thereof ladder steps 4c having a substantially trapezoidal or circular segment plan configuration. Thus, while the inner elements 5c could be substantially like the preceding inner elements, the outer elements 6c will have a different construction, both with respect to the different extension of said elements 6c and due to the provision thereon of bent portions along one or more vertical lines 28, 29. From the preceding disclosure it should be apparent that the modular step unit and self-supporting ladder construction according to the present invention fully achieve the intended aim and objects. In particular, it should be pointed out that a ladder construction having a great resistance against oscillations and vibrations, owing to the sandwich provided construction and the provision of several flat coupled elements, has been provided. Moreover, it should be also pointed out that the height of the ladder construction can be easily and quickly varied without affecting the geometrical configuration of the prefabricated components. While the modular unit and self-supporting ladder construction according to the invention have been disclosed and illustrated with reference to the accompanying drawings, it should be apparent that they would be susceptible to several modifications and variations all of which will come within the inventive scope as claimed in the accompanying claims. If ladder constructions of great width must be used, then it would be possible to use more than two bearing structures 3, by adjoining each side bearing structure and several middle bearing structures, coupled to the other side bearing structure, by coupling cross-members 4a. In this connection it should be apparent that the cross-member 4a, coupling the bearing or supporting structures 3, can comprise either a plate-like or a tubular element. Moreover, it should be pointed out that the modular unit according to the present invention allows to easily made plate-like vertical modular units 5, in which suitable slots 22 delimited by two vertical portions and two curved portions with a convexity respectively facing upward and downward would be formed, thereby providing likewise contoured insert 43 to be provided with corresponding holes at set levels, with respect to the longitudinal extension of said inserts 43. In particular, in the subject modular unit, the inserts 43 would be directly formed by shearing or cutting operations on vertical plate-like modular units 5, which would be provided with calibrated housing seats 22 for engaging therein the mentioned inserts 43. Said inserts would be provided with a plurality of holes arranged at the center thereof, or at a top and/or bottom position with respect to the longitudinal extension of said inserts 43 thereby allowing to easily adjust the height of the individual ladder steps. Finally, the mentioned inserts 43 could be easily engaged in the seats 22, which would be provided with a corresponding configuration.

Claims: A modular step unit, specifically designed for metal self-supporting ladder constructions, comprising a side supporting means (3, 3c) supporting a flat ladder step (4, 4c), coupling means (16) for coupling each modular unit to an adjoining modular unit for defining a self-supporting ladder ramp (1, 1c), said side supporting means (3, 3c) comprising at least a substantially vertical inner element (5) arranged between and rigidly coupled to at least a pair of substantially horizontal outer elements (6, 6c), at least an inner element (5) being adapted to be coupled to at least a pair of outer elements (6, 6c) pertaining to an adjoining modular unit (3, 3c) by a coupling device (16) which can be adjusted in height in order to provide a variable height ladder ramp, characterized in that said side supporting means comprise a pair of side supporting structures, in that said inner and 'outer elements (5, 6; 6c) comprise metal plates having a substantially constant thickness and a substantially rectangular plan shape and being arranged on mutually spaced vertically extending planes, and in that said substantially horizontal outer elements (6, 6c) are provided, near a front corner of a ladder step, with a downward directed lug (7) defining with a bottom edge thereof a vertical spacer for an adjoining side structure. A modular unit according to Claim 1, characterized in that each inner element (5) is coupled to said outer elements at said cross lug (7) by fixed coupling elements (11). A modular unit according to Claim 2, characterized in that said unit comprises standardized outer elements (6', 6", 62"') having cross lugs (7', 7") of different heights (D', D", D"') depending on the ladder step height range. A modular unit according to Claim 1, characterized in that outer elements (6) are substantially flat in order to provide straight ladder ramps, or bent (6c) along at least a substantially vertical generatrix (28, 29) thereof to provide curved, mixed or helical ladder ramps. A modular unit according to Claim 2, characterized in that each adjustable coupling device (16) comprises an insert (17) which can be engaged in a complementary shape cavity (21) formed in each inner element (5). A modular unit according to Claim 5, characterized in that said insert (17) is provided, on respective faces thereof, with substantially horizontal tooth arrangements (21) having a set pitch and a throughgoing hole (20) which is elongated in a substantially vertical direction. A modular unit according to Claim 6, characterized in that each adjustable coupling device (16) comprises a pair of plates (23) arranged between at least an inner element (5) and an adjoining outer element (6). A modular unit according to Claim 7, characterized in that said plates (23) are provided with tooth arrangements (25) identical to those (21) of said insert (17) for cooperating therewith, and a central hole (25) of circular shape, having a diameter equal to the minimum diameter of the elongated hole (20). A modular unit according to Claim 8, characterized in that the tooth arrangement (25) formed on each plate (23) is eccentrically arranged with respect to the axis (B) of its hole (24) in order to allow a maximum height variation with respect to the insert (17) by turning through 180° the plate (23) about the axis of the hole (24) thereof. A modular unit according to Claim 9, characterized in that each adjustable coupling device (16), formed by an insert (17) and a pair of plates (23) is locked in a set position by fixed coupling elements (10) passing through said throughgoing holes (20, 24) in order to clamp their respective facing tooth arrangements (21, 25) by height adjusting their related positions. A modular unit according to Claim 10, characterized in that said fixed coupling elements (10) comprise a cylindric pin (11) having inner threaded end portions for engaging therein respective locking screws (12, 13). A modular unit according to Claim 11, characterized in that the head of the screws (11,12) are engaged in complementary shape seats as formed on the outer faces of said outer elements (6) thereby said screw head are flush with the latter. A modular unit according to Claim 1, characterized in that each side supporting structure (3) comprises a pair of inner elements (5) coupled to a pair of outer elements (6) spacing washers (14) being arranged between each element and immediately adjoining element. A modular unit according to Claim 11, characterized in that said pair of inner elements (5) is coupled to a pair of outer elements by a pair of coupling elements (9) arranged along a line which is slanted at 45° with respect to a horizontal line. A modular unit according to Claim 1, characterized in that at least one of said outer elements (6) of each supporting structure (3) is provided with a support (15) for one or more cross members (4a) for bearing thereon a ladder step (4) and an anchoring bracket for anchoring upright elements (26) of a guard or parapet (27). A modular unit according to one or more of the preceding claims, characterized in that said modular unit comprises a plurality of plate-like vertical modules, in which are formed a plurality of slots delimited by two vertical portions and two curved portions, with a convexity respectively facing upward and downward, thereby providing corresponding inserts of like shape including a plurality of throughgoing holes at different levels or heights with respect to the longitudinal extension of said inserts. A modular unit according to one or more of the preceding claims, characterized in that said inserts with directly made by shearing or cutting operations on vertical plate-like modules, said modules being provided with calibrated housing seats for engaging therein said inserts. A modular unit according to one or more of the preceding claims, characterized in that said inserts are provided with a plurality of holes arranged at the center or top or bottom thereof, with respect to the longitudinal extension of said inserts, thereby allowing to adjust the height of the individual ladder steps, said inserts being engaged in said seats which are provided with a corresponding configuration. A modular unit according to one or more of the preceding claims, characterized in that said cross member for coupling said supporting structures (3) comprises a plate-like or tubular element. A modular unit according to one or more of the preceding claims, characterized in that , for making great width ladder constructions, said modular unit comprises a number of supporting structures (3) greater than two, wherein each side supporting structure adjoins one or more middle supporting structures, coupled to the other supporting structure by said coupling cross-members (4a).

Inventors: MASTELLA MASSIMO, MASTELLA, MASSIMO
Applicants: MASTELLA MASSIMO, MASTELLA, MASSIMO
Application year: 1999
Main classification: E06C1
IPC codes: E04F11, E06C7, E06C1