Tank car access ladder

Abstract

A portable ladder having a pair of elongate stiles spaced from one another and each having first and second ends, and extending in a first direction; and a plurality of rungs each extending between the elongate stiles transverse to the first direction and having opposed ends one of each attached to each of the elongate stiles and each of the plurality of rungs being spaced from one another along the first direction, the rungs being arcuate in shape between the opposed ends.

We claim: 
     
       1. A portable ladder comprising:
 a pair of elongate stiles spaced from one another and each having a first end and a second end, a topmost surface at the first ends, and the pair of elongate stiles extending in a first direction; 
 a plurality of rungs each extending between the elongate stiles transverse to the first direction and having opposed ends one of each attached to each of the elongate stiles and each of the plurality of rungs being spaced from one another along the first direction, the rungs being arcuate in shape between the opposed ends; and 
 a securing assembly fixedly attached to the topmost surfaces and comprising first and second support bar sections and a centrally disposed curved portion extending from and between the first and second support bar sections; each support bar section having a distal end extending from and spaced in a direction transverse to the first direction outward from the pair of elongate stiles, 
 said curved portion extending rearward of the stiles and the support bar sections extending forward of the stiles; and each support bar comprising a stop projecting from the distal end, the respective stops extending along the first direction and spaced from one another and the stiles. 
 
     
     
       2. The ladder of  claim 1  wherein the stiles have an outer surface and a central portion of each of the plurality of rungs extends in a direction transverse to the first direction outward beyond the outer surface. 
     
     
       3. The ladder of  claim 1  wherein the stiles have a cross-sectional shape selected from the group consisting of a straight line, a curved line, a C-shape, a D-shape, an H-shape, a T-shape, an L-shape, a V-shape, circular, oval, polygonal, and sinusoidal. 
     
     
       4. The ladder of  claim 3  wherein the polygonal shapes include triangular, square, rectangular, trapezoidal, pentagonal, hexagonal, heptagonal, and octagonal. 
     
     
       5. The ladder of  claim 1  wherein the securing assembly is fixedly attached to both of the stiles. 
     
     
       6. The ladder of  claim 5  wherein the securing assembly, further comprising a third stop depending from the curved portion and extending along the first direction. 
     
     
       7. The ladder of  claim 6  wherein a distance between the respective stops of the support bars and the third stop of the curved portion defines a gap. 
     
     
       8. The ladder of  claim 7  wherein the respective stops of the support bars are spaced from each other, to define a wall receiving structure. 
     
     
       9. The ladder of  claim 5  further comprising an arcuate strap spaced from the securing assembly and connected at opposed ends to the stiles. 
     
     
       10. The ladder of  claim 9  further comprising a pair of gussets, one of each gusset connecting the securing assembly to one of the stiles. 
     
     
       11. The ladder of  claim 1  wherein the respective stops of each support bar is generally cylindrical.