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CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a National Stage of International Application No. PCT/EP2006/004848, filed May 22, 2006, and which claims the benefit of German Patent Application No. 102005028885.5, filed Jun. 22, 2005, the disclosures of both applications being incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to steps which are suitable, for example, for use in the construction of buildings or for industrial use and can thus be assembled and disassembled comparatively fast. 
     Construction stairways are known which include a plurality of individual step treads which are connected to one another at the side via fittings. Such a construction stairway can be pulled apart in the manner of a concertina for an intended use as steps and can be folded together in a space-saving manner for transport and for storage. On assembly, the construction stairway is pulled over square timbers in the pulled-apart state, the square timbers then forming the two side strings for the construction stairway and the step treads being able to be fixed to them. 
     Such a construction stairway with square timbers can be assembled fast and easily, but can only be handled with difficulty, and in particular not by a single person, due to its weight. 
     SUMMARY OF THE INVENTION 
     It is an underlying object of the present invention to provide steps which are easy to handle and can preferably be assembled and disassembled by one individual person. 
     This object is satisfied by scaffold steps which have two separate side strings and a plurality of separate step elements which can be releasably coupled both to one another and to the side strings. 
     In accordance with the invention, a plurality of individual parts with relatively low weight are provided in each case which, analog to construction scaffolding, can be assembled to form an intended total unit, in the present case to form steps. The steps assembled from the individual parts can subsequently be dismantled into their individual parts again since the coupling connections of the step elements are made releasable with respect to one another and between the side strings and the step elements. 
     An individual part, which has a much lower weight than the total scaffold steps, can be transported or carried individually and in particular by one single person. The scaffold steps in accordance with the invention can be handled particularly easily due to this and due to the releasable coupling of the individual parts and can be dismantled, in particular at different locations, quickly and easily by one single person. 
     Middle step elements, i.e. step elements which are arranged between a bottommost and an topmost step element in assembled scaffold steps, are in particular coupled both to the step element arranged directly thereunder and to the step element arranged directly above it so that particularly stable and reliable scaffold steps can be provided. 
     At least all the middle step elements and in particular also a bottommost step element can preferably each be coupled to the two side strings. A topmost step element can be made for technical construction considerations such that it cannot be coupled to the side strings, but only to the step element arranged directly thereunder and, optionally, to other components of the scaffold steps, for example to a horizontal latch or to a scaffolding platform. 
     A step element can form precisely one step of the assembled scaffold steps. It is, however, generally also possible for one step element to form two or more steps. 
     In accordance with a preferred embodiment of the invention, with assembled scaffold steps, the step elements are each secured against lift-off by step elements arranged directly above them. Particularly stable and reliable scaffold steps can hereby be provided. A topmost step element can be secured against lift-off by a scaffolding platform adjoining the topmost step element. 
     The scaffold steps can be assembled and disassembled particularly quickly and easily if two step elements can be coupled by threading through, pushing through, plugging in or engaging one or more connection elements of a step element in or through one or more recesses of an adjacent step element. A type of hinge or a rotatable joint can in particular be formed by the connection element and the recess so that the two step elements can be moved by rotation or pivoting relative to one another from a starting position enabling a lift-off of the upper of the two step elements into an end position preventing such a lift-off. In particular no further components such as screws or nuts are necessary to form the coupling connection. 
     A step element preferably has two limbs, in particular seen in cross-section, with one limb being made as a step tread and the other limb being made as a riser for the connection to an adjacent step element which is in particular arranged thereunder. With assembled scaffold treads, the step tread preferably extends at least substantially horizontally such that a person going up or down the scaffold steps can find a secure footing. The riser, which preferably extends substantially perpendicularly, can be provided as a type of protective device so that a person cannot move, or cannot move too far, between two adjacent step treads with a foot or even with a leg. 
     In particular at least one connection element, in particular a lug extending away from the limb or from a section thereof in a straight or oblique manner or at a right angle, can be provided at one limb and at least one recess can be provided in the other limb, in particular in its end region remote from the one limb, with at least one connection element of the one limb of an adjacent step element, in particular arranged thereunder, engaging into the recess with assembled scaffold steps. 
     In accordance with a further preferred embodiment of the invention, at least one limb is angled along at least one edge extending in the transverse direction of a step element. The end region of the step tread remote from the riser can, for example, be angled upwardly so that a person can haptically recognize the depth of the riser. A section of the riser can be angled rearwardly to increase the depth of the step tread. Additionally or alternatively, a section, in particular a smaller section, of the riser can be forwardly angled to form a security against lift-off. 
     Step elements can preferably each be manufactured from one single areal element by stamping and bending; i.e. the step elements are each made in one piece. The step elements can thereby be manufactured particularly easily. 
     To be able to grip, carry and handle the step elements particularly easily, a respective gripping opening can be formed in step elements, in particular in risers. 
     Holding devices can be formed, in particular attached, preferably welded, to both side strings for the holding of step elements. Respective holding devices are preferably provided at least for the middle step elements and the bottommost step element. 
     A holding device can have at least one projection which in particular projects upwardly from the side string, and is preferably of hook-shape, mushroom-shape or pin-shape and engages into a lateral cut-out of a step element or into a lateral opening of a step element in the assembled scaffold steps. A security against lift-off can be achieved for the respective step element by the engagement of the projection into the cut-out or into the opening. The step element can preferably be moved by rotation or pivoting into an end position in which the projection engages into the cut-out or the opening. In particular no further components such as screws or nuts are necessary to form the coupling connection between the step elements and the side strings. 
     It is particularly advantageous if a holding device has two projections, in particular arranged sequentially, with in particular one projection engaging into a lateral cut-out and the other projection engaging into a lateral opening. The engaging sections of the two projections preferably face one another so that the step element, in particular its riser, is arranged between the two projections with assembled scaffold steps in order thus to prevent a movement of the respective step element in the longitudinal direction of the scaffold steps. 
     The holding devices provided at the side strings can in particular additionally have a respective support surface on which at least a part of a step element, in particular a limb formed as a step tread, can be supported. It is hereby achieved that the larger part of the weight which acts on a step element on loading is directly supported by the side strings and does not have to be carried by the coupling connections with the adjacent step elements. 
     The one end of the side strings of the scaffold steps in accordance with the invention can generally be supported at the base, for example, and the other end can be fixed to a wall, for example. Generally, no further individual parts are thus necessary for the scaffold steps in accordance with the invention. To enable a free erection of the scaffold steps, however, preferably at least four vertical supports and/or at least two longitudinally extending horizontal latches are provide for the connection of two respective vertical supports, with each side string being fastened, in particular releasably fastened, to at least one vertical support and/or to one longitudinally extending horizontal latch. 
     It is furthermore preferred for a branching latch to be formed, in particular attached, preferably welded, to an end of each side string, with the side string being able to be fastened to a vertical support beneath a topmost step element of assembled steps by means of the latch. This allows the actual end of the side string to not have to be fastened to the vertical support so that a fastening position located at the level of the actual end of the side string, for example a rose of a vertical support, can remain free for a horizontal latch of a further level of a scaffolding, in particular with further scaffold steps. 
     A topmost step element can differ in construction from the other step elements. The step tread of the topmost step element can, for example, be made differently or can be completely omitted, in particular when a scaffolding platform adjoins the topmost step element. The topmost step element can furthermore be made such that it cannot be coupled to the side strings. 
     It is furthermore proposed that at least a plurality of step elements are made the same among one another. The middle step elements and the bottommost step element are in particular made the same. A high number of similar components enables a fast and uncomplicated erection, in addition to a cost-effective manufacture, since a time-consuming sorting of the individual parts can be omitted and/or a mixing up of individual parts can hardly ever occur. 
     For the engaging, hooking in or latching in a transversely extending horizontal latch, a limb of a topmost step element extending horizontally in the assembled state can be downwardly angled along an edge extending in the transverse direction of the topmost step element. 
     The side strings, horizontal latches and/or railing elements can preferably be hung to fastening positions, in particular roses of vertical supports. 
     The scaffold steps or parts thereof can be produced from metal, from a metal alloy, from steel, from plastic or from a composite material. 
     The invention will be described in the following by way of example with reference to the drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of scaffold steps in accordance with the invention; 
         FIG. 2  is a perspective view of a middle step element of scaffold steps in accordance with the invention; 
         FIG. 3  is a perspective view of a section of scaffold steps in accordance with the invention with a step element at the start of its assembly; 
         FIG. 4  is a perspective view of a section of scaffold steps in accordance with the invention with an almost completely assembled step element; 
         FIG. 5  is a perspective view of a section of scaffold steps in accordance with the invention with a completely assembled step element; 
         FIG. 6  is a perspective view of the bottommost step element and of a scaffolding platform arranged beneath the bottommost step element; 
         FIG. 7  is a perspective view of the topmost step element and of a scaffold platform adjoining it; 
         FIG. 8  is a cross-section through the topmost step element and a scaffold platform adjoining it and having transversely extending scaffold platform elements; 
         FIG. 9  is a cross-section through the topmost step element and a scaffold platform adjoining it and having longitudinally extending scaffold platform elements; 
         FIG. 10  is a perspective view of scaffolding having a plurality of levels and a plurality of scaffold steps in accordance with the invention; 
         FIG. 11  is a perspective view of a section of scaffold steps in accordance with the invention in accordance with a further embodiment with a step element at the start of its assembly; 
         FIG. 12  is a perspective view of a section of scaffold steps in accordance with the invention in accordance with the further embodiment with an almost completely assembled step element; 
         FIG. 13  is a perspective view of a section of scaffold steps in accordance with the invention in accordance with the further embodiment with a completely assembled step element; and 
         FIG. 14  is a cross-section through the transition region between two step elements of scaffold steps in accordance with the invention in accordance with the further embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The scaffold steps in accordance with the invention shown in the assembled state in  FIG. 1  consist of metal and include a bottommost step element  13 ′, a plurality of middle step elements  13  and a topmost step element  13 ″. The bottommost step element  13 ′ and the middle step elements  13  are all made the same. Only the topmost step element  13 ″ differs in its design. 
     Two respective adjacent step elements  13 ,  13 ′,  13 ″ are releasably coupled to one another. The bottommost step element  13 ′ and the middle step elements  13  are additionally releasably coupled to two side strings  11 . The releasable couplings will be described in more detail at a different point. 
     Furthermore, the scaffold steps in accordance with the invention have three respective multi-part vertical supports  37  at both sides to which roses  49  are respectively attached at predetermined levels. Furthermore, two longitudinally extending horizontal latches  39  are provided at both sides and connect two respective vertical supports  37  to one another. The longitudinally extending horizontal latches  39  are each hung at their two ends to roses  49  of the vertical supports  37 . 
     The one end of the side strings  11  is welded in each case to the longitudinally extending horizontal latches  39  arranged between the front and middle vertical supports  37 . Alternatively, the lower end of the side strings  11  and the longitudinally extending horizontal latch  39  can, however, also be releasably fastened to one another with a U-shaped clamp, known per se, open toward the bottom and fastened to the side string  11 . A respective horizontally aligned branching latch  41  is welded to the upper end of the clamp at the side strings  11 , and the side strings  11  are hung beneath the topmost step element  13 ″ in each case at roses  49  of the middle vertical supports  37  by means of the latch. 
     Furthermore, a scaffold platform  47  is provided which adjoins the topmost step element  13 ″, consists of a plurality of individual platforms and is hung at roses  49  of the middle and rear vertical supports  37 . A further scaffold platform  45  consisting of one single platform is provided beneath the bottommost step element  13 ′. 
     Two railing elements  51  are provided between the front and middle vertical supports  37  on both sides of the scaffold steps in accordance with the invention, the railing elements being hung at rosettes  49  of the front and middle vertical supports  37 , extending parallel to the side strings  11  and serving for the stabilization of the scaffold steps in accordance with the invention and simultaneously as security for persons and as a handrail. 
       FIG. 2  shows a step element  13 ,  13 ′ of the scaffold steps in accordance with the invention as is used for the bottommost step element  13 ′ and the middle step elements  13 . The step element  13 ,  13 ′ is manufactured from an individual metal sheet by stamping and bending and has two limbs  19 ,  21 , with the one limb  19  forming a step tread and the other limb  21  forming a riser. The step tread  19  can, contrary to what is shown in  FIG. 2 , be holed or perforated like the scaffolding platforms  45 ,  47  in order thus in particular to form a protection against sliding. 
     The step tread  19  is upwardly angled along an edge  53  extending in the transverse direction of the step element  13 ,  13 ′, with a dimple  65  being formed at both sides on the angled section. Furthermore, the step tread  19  includes four lugs  15  which are arranged next to one another, which each have an L shape seen in cross-section and which each extend obliquely upwardly away from the step tread  19 . 
     The riser  21 , which has a grip opening  23  for gripping and carrying, is backwardly angled in its end region facing the step tread  19  along an edge  55  extending in the transverse direction of the step element  13 ,  13 ′ and is forwardly angled in its end region remote from the step tread  19  along an edge  57  extending in the transverse direction of the step element  13 ,  13 ′. The section bounded by the edges  55  and  57  has a respective opening  33  at both sides and the forwardly angled section has a respective cut-out  29  at both sides. 
     Furthermore, four window-like recesses  17  are formed in the region of the edge  57  which are arranged next to one another and into which four lugs  15  of the step tread  19  of a step element  13 ,  13 ′ arranged directly thereunder engage with assembled scaffold steps to establish a coupling connection. 
     At each side string  11 , respective holding devices  25  ( FIGS. 3 to 5 ) are provided for the bottommost step element  13 ′ and for each of the middle step elements  13  and serve for the holding of the step elements  13 ,  13 ′ at the side strings  11 . 
     In accordance with  FIG. 4 , one holding device  25  includes two sequentially arranged, upwardly projecting hook-like projections  27 ,  31  which are welded to the side string  11 . With assembled steps, the projection  27  engages into the cut-out  29  and the projection  31  engages into the opening  33  of the corresponding side of a step element  13 ,  13 ′. The engaging sections of the projections  27 ,  31  face one another in this connection. Furthermore, a holding device  25  includes a support surface  35  for the step tread  19  of a step element  13 ,  13 ′ arranged directly thereunder. 
     The holding devices  25  for the bottommost step element  13 ′ have no support surfaces ( FIG. 6 ). The holding devices  25  for the topmost step element  13 ″, in contrast, have no projections ( FIG. 7 ). 
     In accordance with  FIG. 6 , the scaffolding platform  45  arranged beneath the bottommost step elements  13 ′ is fastened to longitudinally extending horizontal latches  39  using conventional cap and securing yokes  59 ,  59 ′ and is thus secured against lift-off in a known manner. 
       FIG. 7  shows the topmost step element  13 ″ and a transversely extending scaffolding platform element of the scaffolding platform  47  adjoining it. The topmost step element  13 ′ is made with two limbs and includes a short step section  19 ′ and a riser  21 . The riser  21  of the topmost step element  13 ″ is formed analog to the riser  21  of the bottommost step element  13 ′ and to the risers  21  of the middle step elements  13 . 
     The step tread section  19 ′ of the topmost step element  13 ″ is, unlike the step tread  19  of the bottommost step element  13 ′ and the step treads  19  of the middle step elements  13 , not angled upwardly, but downwardly ( FIG. 8 ) to enable an engaging, hooking or latching into a transversely extending horizontal latch  43 . As a security against lift-off, the transversely extending scaffolding platform element of the scaffolding platform  47  adjoining the topmost step element  13 ″ is fastened to longitudinally extending horizontal latches  39  using conventional cap and securing yokes  59 ,  59 ′, as can in particular be recognized in  FIG. 7 . 
     If, instead of transversely extending scaffolding platform elements, longitudinally extending scaffolding platform elements are used, the cap yokes  59  ( FIG. 9 ) of the scaffolding platform elements are used as the securing device and are partly guided through orifices  63  ( FIG. 7 ) of the step tread  19  of the topmost step element  13 ″ to enable a fastening at the transversely extending horizontal latch  43  at which the step tread  19  of the topmost step elements  13 ″ is hung. 
     The assembly of scaffolding steps in accordance with the invention will be explained below with reference to the drawing. 
     First, the vertical supports  37  are erected and the step strings  11 , in particular their branching latches  41 , and the horizontal latches  39 ,  43  are hung at roses  49  of the vertical supports  37 . 
     Subsequently, the scaffolding platform  45 , which is arranged beneath the bottommost step element  13 ′ with assembled scaffold steps, is placed in and is fastened by means of support and securing yokes  59 ,  59 ′ to longitudinally extending horizontal latches  39  and is thereby secured against lift-off. 
     Subsequently, the bottommost step element  13 ′ is oriented such that the riser  21  is aligned approximately horizontally. The bottommost step element  13 ′ is moved from this starting position by turning of the lateral cut-outs  29  and the openings  33  of the riser  21  into the two projections  27 ,  31  into an end position which will be explained in more detail in the following in connection with the middle step elements  13 . At the same time, the step tread  19  of the bottommost step element  13  lies on the support surfaces  35  of the next higher holding devices  25 . 
     Next, a first middle step element  13  is assembled. For this purpose, the first middle step element  13  is likewise oriented such that the riser  21  is aligned approximately horizontally, as is shown in  FIG. 3  for any desired middle step element  13 . For the releasable coupling of the middle step element  13  with the step element  13 ,  13 ′ disposed thereunder, the lugs  15  of the lower step element  13 ,  13 ′ are first threaded into the recesses  17  of the upper step element  13  or are plugged therethrough. Subsequently, the upper step element  13  is moved from this starting position ( FIG. 3 ) by being set upright into an end position ( FIG. 5 ), with the lateral cut-outs  29  and grips  33  of the riser  21  being turned into the two projections  27 ,  31  on this movement until the step tread  19  of the first middle step element  13  lies on the support surfaces  35  of the next higher holding devices  25 . The cut-outs  65  ( FIG. 2 ) of the step tread  19  enable the step tread  19  to be turned past the projection  27  in the assembly. The first middle step element  13  secures the bottommost step element  13 ′ against lift-off. 
     Then all the other middle step elements  13  are assembled step-wise in the same procedure, with a step element  13 ,  13 ′ in each case being secured by the step element  13  arranged directly above it with assembled scaffolding steps. 
     Once all middle step elements  13  are assembled, the topmost step element  13 ″ is assembled. For this purpose, the recesses  17  of the topmost step elements  13 ″ are threaded into the lugs  15  of the last middle step element  13 , and the topmost step element  13 ″ is set upright and is rotated via a transversely extending horizontal latch  43 . The topmost step element  13 ″ secures the last middle step element  13  against lift-off. 
     The topmost step element  13 ″ is itself secured against lift-off with assembled scaffold steps by the directly adjoining scaffolding platform  47  which is fastened by means of conventional cap and securing yokes  59 ,  59 ′ at longitudinally extending or transversely extending horizontal latches  39 ,  43 . 
     Finally, or alternatively also before the assembly of the step elements  13 ,  13 ′,  13 ″, the railing elements  51  are assembled by hanging at rosettes  49  of the vertical supports  37 . 
     In  FIG. 10 , a scaffolding is shown having a plurality of levels A to D which each have steps in accordance with the invention. The advantage of a latch  41  branching off beneath the actual end of the side strings  11  in particular becomes clear from  FIG. 10 . The rose  49  arranged at the level of the scaffolding platform  47  hereby remains unoccupied at the corresponding position so that a longitudinally extending horizontal latch  39  of a further level can be hung in. 
     In  FIGS. 11 to 14 , scaffold steps in accordance with the invention in accordance with a further embodiment are shown. The above description with respect to  FIGS. 1 to 10  can be transferred identically to the further embodiment to the extent that it does not contradict  FIGS. 11 to 14 . In the following, in particular only differences of the further embodiment with respect to the embodiment shown in  FIGS. 1 to 10  are explained. Like or corresponding parts are designated with the same reference numerals. 
     A step element  13 ,  13 ′ in accordance with the further embodiment of the invention, in particular a lower and/or a middle step element, substantially corresponds to a step element  13 ,  13 ′, as is shown, for example, in  FIG. 2 . With respect to the step element  13 ,  13 ′ of  FIG. 2 , in accordance with  FIG. 11 , the lugs  15  and the recesses  17  are arranged actually reversed with respect to the step tread  19  and the riser  21 ; i.e. the step tread  19  has a plurality of recesses  17  arranged next to one another and respectively formed at the section upwardly angled by the edge  53  and the riser  21  has a plurality of lugs  15  which are L-shape seen in cross-section, which are arranged next to one another and extend in each case downwardly obliquely away from the section of the riser  21  angled forwardly by the edge  57 , with only one recess  17  and one lug  15  being shown in  FIG. 11 . 
     Furthermore, the step tread  19  of the step element  13 ,  13 ′ has in each case on both sides a stamped hole  67  at its upwardly angled section. The riser  21  of the step element  13 ,  13 ′ has in each case on both sides a cut-out  29  formed as an elongate hole at its forwardly angled section, with the elongate hole  29  having a circular extension at one end ( FIGS. 12 ,  13 ) to enable a passing through of the head of a mushroom-shaped projection, as will be explained in more detail at another point. 
     The riser of a topmost step element, not shown, in accordance with the further embodiment of the invention is made in accordance with the riser  21  of a lower and/or of a middle step element  13 ,  13 ′ in accordance with the further embodiment of the invention. 
     A holding device  25  in accordance with the further embodiment in particular includes, in accordance with enlarged representations in  FIG. 11 , an upwardly projecting mushroom-shaped projection  27  welded to the side strings  11  and having a head which engages into the elongate hole  29  of the corresponding side of a corresponding step element  13 ,  13 ′ with assembled steps. 
     Furthermore, the holding device  25  includes a further upwardly projecting mushroom-shaped projection  27  welded to the side strings  11  and having a head which engages into the stamped hole  67  of the corresponding side of a corresponding step element  13 ,  13 ′ for the locking of the step tread  19  with assembled steps. 
     For the assembly of a step element  13 ,  13 ′ in accordance with the further embodiment, the step element  13 ,  13 ′ is first oriented such that the step tread  19  is aligned approximately horizontally. Then, the projection  27  is introduced into the circular extension of the elongate hole  29  whose diameter is matched to the diameter of the head of the projection  27  ( FIG. 11 ). 
     Subsequently, the step element  13 ,  13 ′ is moved along the longitudinal direction of the side strings  11  so that the head of the projection  27  cooperates with a section of the elongate hole  29 , wherein the width of the elongate hole  29  is smaller than the diameter of the head, with simultaneously the lugs  15  of the step element  13 ,  13 ′ to be assembled being plugged into the recesses  17  of the step element  13 ,  13 ′ arranged thereunder, the recesses not being visible due to the selected perspective ( FIG. 12 ). 
     Finally, the step element  13 ,  13 ′ is pivoted slightly around an axis extending in the transverse direction to achieve an engagement of the further projection  27  into the stamped hole  67  of the step tread  19  ( FIG. 13 ) in order thus to prevent a displacement of the step element  13 ,  13 ′ along the longitudinal direction of the side strings  11 . 
       FIG. 14  shows an upper step element  13 , shown not hatched, and a lower step element  13 ,  13 ′, shown hatched, which are coupled to one another. For this purpose, the lugs  15  of the upper step element  13  engage or are plugged into the recesses  17  of the lower step element  13 ,  13 ′. The section of the lower step element  13 ,  13 ′ upwardly angled by the edge  53  is clamped in the manner of pliers by the lug  15  and the section of the upper step element  13  forwardly angled by the edge  53 . 
     REFERENCE NUMERAL LIST 
     
         
           11  side string 
           13  middle step element 
           13 ′ bottommost step element 
           13 ″ topmost step element 
           15  lug 
           17  recess 
           19  step tread 
           19 ′ step tread section 
           21  riser 
           23  grip opening 
           25  holding device 
           27  projection 
           29  cut-out 
           31  projection 
           33  opening 
           35  support surface 
           37  vertical support 
           39  longitudinally extending horizontal latch 
           41  branching latch 
           43  transversely extending horizontal latch 
           45  scaffolding platform 
           47  scaffolding platform 
           49  rose 
           51  railing element 
           53  edge 
           55  edge 
           57  edge 
           59  cap yoke 
           59 ′ securing yoke 
           63  orifice 
           65  dimple 
           67  stamped hole

Summary:
The invention relates to scaffold steps, with two separate side pieces ( 11 ) and a plurality of separate step elements ( 13, 13′, 13 ″), which can be detachably coupled to each other and to the side pieces.