Assemblies comprising foot rungs, for example for ladders
United States Patent 11 1 Gubri Apr. 29, 1975 1 ASSEMBLIES COMPRISING FOOT RUNGS.  
 FOR EXAMPLE FOR LADDERS [76] Inventor: Leon Gubri, 42-44, rue Emile Deschanel, Courbcvoie, France, 92404 22 Filed: July 13, 1973 211 App]. No.: 378,944  
 [52] U.S. Cl. 182/228; 182/194 [51] Int. Cl. E06c 7/08 [58] Field of Search 182/228 [56] References Cited FOREIGN PATENTS OR APPLICATIONS 975,093 11/1964 United Kingdom 182/228 1,550,157 11/1967 France 182/228 1.919643 4/1969 Germany 182/228 1,376,694 9/1964 France 182/228 Primary E.raminerRein aldo P. Machado Attorney, Agent, or Firm-Larson, Taylor and Hinds [57] ABSTRACT The rungs are of polygonal shape and are introduced, on assembly, into openings of corresponding shape, provided in the uprights of the ladder. Fixing is then effected by beading over. The rungs have a crenalated shape and their thickness is slightly increasing towards the edges of the polygonal section. The devices are useful for any ladders for building, household work,  
 etc.  
 6 Claims, 3 Drawing Figures PATENTEU 3.880257 ASSEMBLIES COMPRISING FOOTRUNGS, FOR EXAMPLE FOR LADDERS The invention relates to improvements in or to assemblies, especially for ladders, comprising foot rungs.  
  It has already been proposed to give the external cross-section of the rungs a polygonal shape, for example square, the sides of the cross-section receiving a concave shape.  
  It has also been proposed, to ensure fixing of such rungs, on the uprights of a ladder or other assembly, to cut them out at their ends in order to give them there a circular shape, the end being introduced, on fixing, into holes of the same shape formed in said uprights.  
  According to the present invention, this cut-out is eliminated, so that the polygonal shaped rung is introduced, by its ends, on fixing, directly into holes of substantially the same shape, pierced in the abovesaid uprights, such an arrangement enabling simplification of manufacture whilst ensuring positive connection, especially for the reason that, due to the holding of the polygonal shape, the rungs are prevented from turning around their axis.  
  The invention consists, apart from this main feature, of certain other features which are preferably used at the same time and which will be more explicitly considered below.  
  The invention will in any case be well understood with the aid of the complement of description which follows, as well as of the accompanying drawing, which complement and drawings are, of course, given primarily by way of indication.  
  FIG. 1 of this drawing shows in elevation one embodiment of the ladder constructed according to the invention.  
  FIGS. 2 and 3 show, on a larger scale and partially, respectively in lateral view and in section through the lines III-Ill of FIG. 2, the assembly ofa rung and of one of the uprights of the ladder-according to the invention.  
  According to the invention and more especially according to that of its types of application, as well as according to those embodiments of its various parts, to which it appears that preference should be given, in order for example to provide a ladder, especially metallic (in particular of aluminum or another light alloy), or a part of a ladder, constituted essentially by the assembly of tubular rungs l of polygonal external general cross-section, for example square, preferably with at least certain concave sides, on uprights for example also tubular 2 (Figure 1), procedure is as follows or in analogous manner.  
  Advantageously the abovesaid rungs are manufactured by threading or extrusion (or any other method such as drawing, molding, machining, etc.) by making them include on the outside channels or grooves 3, 4, the assembly being inserted for example inside a prism which the contour A B C D of the transverse section comprises for example two rectilinear sides AD, BC and two curvilinear sides (for support of the feet) AB, DC, whilst the inner surface can be of round crosssection, and as regards the fixing of these rungs on the hollow upright 2, instead of having recourse to cuttingout, the ends of the rungs are directly engaged (FIG. 2) in opposed openings of corresponding polygonal shape formed by cutting-out (or any other means) in the corresponding walls of said uprights, fixing then being effected by any suitable method, for example by beading over, as shown at 11 .in FIG. 3.  
  It is understood that the opposed openings or holes 10 abovementioned could comprise notches corresponding to the abovesaid grooves or channels, but this is not essential, since the fact alone of the polygonal shape of the outer cross-section A B CD suffices to ensure stable fixing, without the rung&#39; being able to turn around itsaxis.  
  The operation of beading&#39;over or any other possible operation of finishing could easily close up, if necessary, the interstices existing between the contour A B C D of the hole 10 (when the sides of this contour are continuous) and the bottom of the grooves 4.  
  In the embodiment shown, the curvilinear surfaces AB, DC have for example a radius of the order of three times the internal radius of the rung. As for the rungs and the grooves 3, 4, their depth can be possibly variable, so that the thickness of the metal tends to increase slightly towards the corners of the contour A B C D. These corners will of course be rounded, to render support of the feet more comfortable. On the rectilinear surfaces AD, BC, the said channels can be reduced to the minimum, even eliminated.  
  It is helpful to define the outer boundary of the solid thickness portion of the ring. On a side where there are no channels, this would be defined by the outer surface of that side, for example the vertical sides of the rung in the embodiment where no channels are provided on such sides. On sides with channels this boundary would be defined by a line such as the dotted line X in FIG. 2 which connects the bases of the channels for the side AB.  
  As a result of which and whatever the embodiment adopted, ladders are obtained whose operation emerges sufficiently from the foregoing for it to be unnecessary to dwell further on this subject, and which have with respect to those pre-existing of the type concerned, numerous advantages, for example:  
  that of enabling simpler construction and more rapid fixing,  
  that of enabling the obtaining of more rigid rungs, due to increase in the cross-sections along the edges A B C D,  
  that of avoiding any possibility of rotation of the rungs around their axis,  
  that of ensuring surer and more comfortable support to the feet, whatever the inclination of the ladder.  
  As is self-evident, and as emerges already from the foregoing, the invention is in no way limited to those of its types of application and embodiments which have been more especially envisaged; it embraces, on the contrary, all modifications.  
 I claim:  
  1. A ladder comprising opposed uprights having pairs of opposed openings, a plurality of elongated hollow rungs, each rung having a prismatic generally rectangular external surface, as viewed in cross-section transverse to the direction of elongation thereof, and including a plurality of channels formed in and extending longitudinally along at least the upper surface of the rung, to define upstanding ribs, each rung extending through and being fixedly engaged in opposed openings of a pair, the openings being essentially the same shape and size as the said generally rectangular outer transverse cross-section of the rung received therein, the rungs contacting the edges of each of its respective openings at least in part on all four sides thereof, and at allfour corners thereof, wherein on &#34;any of said four sides which include channels and ribs, ribs are provided at both; corners adjacent to that side to effect said con- .tacting at those corners, wherein each rung fits snuggly in bothofits respective openings,  
 . each said rung having a circular cylindrical internal surface, the center of which is coincident with the axis of the prismatic external surface, the thickness of the rung between thesaid internal surface and the solid thickness boundary thereof, viewed in transverse crosssection, continuously increasing from a minimum at the center ofeach side of the rung towards either adjacent edge of that side to a maximum at both adjacent corners of the rung, so as to provide an increased solid thickness of material at the corners of the rung relative to thethickness at the said center of each side, to resist deformation of the rungs at said corners.  
 2. A ladder according to claim 1, said channels being provided along both the upper and lower surfaces of the rung.  
  3. A ladder according to claim 2, said channels also being provided along the essentially vertical sides of the rung.  
  4. A ladder according to claim 1, the said uprights being hollow and essentially rectangular when viewed in transverse cross-section, and means for fixedly connecting each end of each rung with the uprights by flanging the outer surfaces of the rungs within the rectangular cross-section of the uprights.  
  5. A ladder according to claim 1 wherein said prismatic rectangular external surface of each rung&#39;is essentially square 6. A ladder according to claim 1, wherein the upper and lower surfaces of the rung are curved and the two sides are straight