Railcar having cold formed center sill with stiffness enhancing structure

Abstract

A railcar comprising: a plurality of truck assemblies, each truck assembly having at least one wheel an underbody supported on said truck assemblies, said underbody including a cold formed center sill extending substantially the length of said railcar, wherein said center sill includes a top wall, a pair of side sections joined to the top wall by a pair of upper curved sections, bottom sections coupled to the side sections through curved connecting sections, wherein the center sill includes an upwardly extending stiffening longitudinal rib centered within the top wall.

Claims

1. A railcar comprising: a plurality of truck assemblies, each truck assembly having at least one wheel; and an underbody supported on said truck assemblies, said underbody including a cold formed center sill extending substantially the length of said railcar, wherein said center sill includes a top wall, a pair of side sections joined to the top wall by a pair of upper curved sections, bottom sections coupled to the side sections through curved connecting sections, wherein the improvement comprises an upwardly extending stiffening longitudinal rib centered within the top wall, and wherein the upwardly extending stiffening longitudinal rib centered within the top wall includes a left and right transition segment extending to a central flat land.

2. The railcar according to claim 1, wherein the central flat land is generally aligned with an opening defined between the bottom sections.

3. The railcar according to claim 2, wherein the central flat land is wider than the opening.

4. The railcar according to claim 3, wherein center sill is formed of 0.5″ stainless steel and wherein the upwardly extending stiffening longitudinal rib centered within the top wall is a stiffening structure that increases the overall height of the center sill to 13.938″ and the overall density of the center sill 70 is 82.3 lbs/ft.

5. The railcar according to claim 1, further including a pair of reinforcing plates welded in the interior only adjacent the draft arm ends and extending for a few feet to stop about at a floor intersection of the railcar.

6. The railcar according to claim 5, wherein the reinforcing plates are aligned with a top surface of an adjacent draft arm.

7. The railcar according to claim 6, wherein the reinforcing plates are configured to convey forces down to the floor intersection.

8. The railcar according to claim 1, further including a pair of a pair of outwardly extending longitudinal side ribs centered within each side wall.

9. The railcar according to claim 8, wherein each outwardly extending longitudinal side rib includes a top and bottom transition segment extending to a central flat land generally centered on the side wall.

10. The railcar according to claim 9, wherein the overall width of the center sill (70) is 15.313″ and the overall density of the center sill (70) is 83.7 lbs/ft.

11. A railcar comprising: a plurality of truck assemblies, each truck assembly having at least one wheel; and an underbody supported on said truck assemblies, said underbody including a cold formed center sill extending substantially the length of said railcar, wherein said center sill includes a top wall, a pair of side sections joined to the top wall by a pair of upper curved sections, bottom sections coupled to the side sections through curved connecting sections, wherein the improvement comprises an upwardly extending stiffening longitudinal rib centered within the top wall, and further including a pair of outwardly extending longitudinal side ribs centered within each side wall.

12. The railcar according to claim 11, wherein each outwardly extending longitudinal side rib includes a top and bottom transition segment extending to a central flat land generally centered on the side wall.

13. The railcar according to claim 12, wherein the overall width of the center sill (70) is 15.313″ and the overall density of the center sill (70) is 83.7 lbs/ft.

Description

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(1) FIG. 1 is a side elevation section view of a prior art C-shaped center sill;

(2) FIG. 2 is a side elevation section view of a prior art Hat or Z-shaped center sill;

(3) FIG. 3 is a side elevation section view of a prior art cold formed center sill;

(4) FIG. 4 is a side elevation section view of a proposed prior art cold formed center sill with internal ribs;

(5) FIG. 5 is a side elevation view of a railcar having cold formed center sill with stiffness enhancing structure according to one embodiment of the present invention;

(6) FIG. 6 is a side elevation section view of a cold formed center sill with stiffness enhancing structure according to one embodiment of the present invention usable with the railcar of FIG. 5;

(7) FIG. 7 is a side elevation section view of a cold formed center sill with stiffness enhancing structure according to another embodiment of the present invention usable with the railcar of FIG. 5;

(8) FIGS. 8A and 8B are a side elevation section views of a cold formed center sill with stiffness enhancing structure according to another embodiment of the present invention usable with the railcar of FIG. 5; and

(9) FIG. 9 is a side elevation section view of a cold formed center sill with stiffness enhancing structure according to another embodiment of the present invention usable with the railcar of FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(10) Referring to FIG. 5, there is illustrated a railroad gondola car 60 for carrying commodities such as coal, gravel and the like and having an underbody carried by opposed truck assemblies 62. The underbody of the railroad car 60 of the invention includes a continuous cold formed center sill 70 with stiffness enhancing structures according to the present invention and which is extending substantially the entire length of the car 60:

(11) A railcar body 80 is attached to the underframe. As will be apparent from the following description, the cold formed center sills 70 of several embodiments of the invention provide significant advantages over prior center sills and contribute to a lightweight, economical car design. Although the center sills 70 of the invention are shown with reference to the gondola car of FIG. 5 by way of illustration, it is within the scope of the invention to use the center sill 70 herein disclosed with any type or design of railcar in which the advantages of the invention are desired. Essentially any railcar having a through center sill (not a stub sill) could utilize the center sill 70 of the present invention.

(12) The cold formed center sills 70 of the present invention with stiffness enhancing structures will generally increase in weight over a cold formed center sill 30 of the same grade and thickness and profile not having the stiffness enhancing structures, however the benefits of including the stiffness enhancing structures outweigh the extra weight of the sill 70 itself. Increasing the stiffness of the center sill 70 over an analogous sized sill 30 will allow the center sill 70 of the invention to absorb more of the coupler load and uniformly transfer this higher load to the next railcar, thereby minimizing the forces to be carried in the extraneous structural members of the railcar 60 like the side sill and other structures, thereby allowing for overall weight reduction to the car due to substantial weight savings in extraneous components.

(13) In FIG. 6 is illustrated the first embodiment of the cold formed center sill 70 including stiffness enhancing structures of the invention. The center sill 70 is formed from suitable steel by a cold forming process. The process may be a cold rolling process through a series of rolling mills, or alternatively the shape may be made in two pieces joined together with each steel member being formed on a hydraulic brake or press. The center sill 70 may thus be formed in a generally rectangular configuration from one or two flat one-piece plate or coiled sheet of steel and the center sill 70 is continuous along its length. The center sill 70 is formed by bent sections created in the cold forming process from a material having a thickness of between ¼ up ¾ ″ with ⅜ inch to ⅝ inch being preferable, and 0.4-0.5″ being most preferred. The center sill 70 according to this embodiment includes an upper top wall 82 and a pair of flat side sections or webs 84, each of generally constant thicknesses.

(14) The top wall 82 and pair of side sections or webs 84 are joined together at right angles by upper curved sections 86 being formed about a common radius such between about 0.75 and 1″ radius. The bottom sections 88 of the center sill 70 are inwardly formed horizontally at right angles to the side sections 84 through curved connecting sections 90 being of constant radius between about 0.75 and 1″ radius. The bottom sections 88 terminate in a pair of upright internal flange portions 92 extending upward and being joined to bottom portions by curved sections 94 of constant radius. Spaced between the internal upright flanges is a longitudinal opening 100 through which access to a apace within the center sill 70 is provided. By way of example, the bottom sections 88 forming the bottom portions of the center sill 70 may each extend approximately 4 inches from the side sections 84 with the opening 100 sufficient to receive a huck gun therein for assisting railcar manufacturing. The center sill 70 is preferably formed of steel having an average yield strength throughout its length of 50,000 to 80,000 PSI. The stiffening structures in the center sill 70 of the present invention more easily accommodates use of 50,000 PSI to be utilized, however the use of higher PSI steels can yield great weight savings for the overall railcar 60. For other reasons the 50,000 PSI is often generally preferred by customers in the industry, although weight savings is also desired, so the selected PSI of the steel remains a tradeoff.

(15) The curved sections 86, 90, 94 are cold worked numerous times during the cold rolling process. As a result, the material is cold hardened and strengthened at sections as compared to its original unformed state. The resulting cross section does not require thicker sections or added material as in the prior art C shaped and Z shaped center sills 10, 20 and provides a high-strength member.

(16) The key feature of the present invention is the provision of an outwardly or upwardly extending offset or stiffening longitudinal rib centered within the top wall 82. The offset includes a left and right transition segment 96 extending to a central flat land 98 generally aligned with the opening 100 and wider than the opening 100. The offset is a stiffening structure that increases the overall height of the center sill 70 to 13.938″ and the overall density of the center sill 70 is 82.3 lbs/ft with 0.5″ thickness steel. This compares with 78.4 lbs/ft for a conventional cold rolled center sill 30 of 0.5″ thick steel of 12.938″. The offset increases the bounded area or envelope of the center sill 70 that tends to improve resistance to buckling. For example in a 0.4″ thick steel version of this embodiment of the present invention the envelope or bounded area is 18.9503 square inches and the conventional envelope of the same thickness (without the stiffener or offset) is 18.7583 square inches. The offset yields, for this particular configuration, greater than 1% increase in the bounded envelope and an associated increase in resistance to buckling forces.

(17) The center sill 70 of the present invention was compared with a prior art cold formed center sill 30 and a C center sill 10 and a Z Center Sill 20. Each center sill 70, 30, 10, 20 was analyzed using 1″ tetrahedronal elements in ANSYS brand software. Remote displacements were placed at each end of the center sill 70, 30, 10, 20 and a downward force of 1000 lbs was applied to the top surface. The maximum stress and maximum deflection are presented in the table below for each center sill 70, 30, 10, 20, along with the weight per foot.

(18) TABLE-US-00001 Stress Deflection Weight (psi) (in) (lbs/ft) Standard RF 18,988 2.38 78.4 Center Sill C Center Sill 15,384 2.05 82.5 Z Center Sill 15,304 2.05 82.5 New RF Center 15,974 2.04 82.3 Sill

(19) As noted in the analysis above, the deflection of the center sill 70 of the present invention is less than that of the standard cold formed center sill 30 and is actually better than the conventional C center Sill 10 or Z Center Sill 20 of similar thickness (0.5″ plate). Additionally the weight per foot is less than the conventional C Center Sill 10 and Z Center Sill 20, although not as light as the conventional cold formed center sill 30. The center sill 70 of the present invention still significantly reduces the weight of the overall railcar 60. Additionally the profile of the present invention can be efficiently formed and yields the improved results described above.

(20) A second embodiment of the center sill 70 including stiffness enhancing structures of the invention is shown in FIG. 7. The center sill 70 is formed from suitable steel by a cold rolling forming process, such as cold rolling or cold pressing. Cold pressing would be using two steel members in a hydraulic brake or series of brakes. The center sill 70 is formed by bent sections having a thickness as discussed above. The center sill 70 includes an upper top wall 82 and a pair of side sections or webs 84, each of generally constant thicknesses. The configuration exceeds the strength characteristics of the preceding embodiment for the same dimensions and material and is also preferably continuously formed from a one-piece coiled sheet or plate or as a two piece structure.

(21) As with the first embodiment the top wall 82 and pair of side sections 84 are joined together at right angles by upper curved sections 86 being formed about a common radius. Similarly, the bottom sections 88 of the center sill 70 are inwardly formed horizontally at right angles to the side sections 84 through curved connecting sections 90 being of constant radius. The bottom sections 88 terminate in a pair of upright internal flange portions 92 extending upward and being joined to bottom portions 88 by curved sections 94 of constant radius. Spaced between the internal upright flanges 92 is a longitudinal opening 100 through which access within the center sill 70 is provided. The center sill 70 preferably possesses an average yield strength as discussed above.

(22) Like the first embodiment of the present invention, a key aspect of the invention is the provision of an outwardly or upwardly extending offset or stiffening longitudinal rib centered within the top wall. The offset includes a left and right transition segment 96 extending to a central flat land 98 generally aligned with the opening 100 and wider than the opening 100. The offset is a stiffening structure that increases the overall height of the center sill 70 to 13.938″.

(23) The difference between the first embodiment and the second embodiment of the present invention is the inclusion of a pair of outwardly extending side offsets or stiffening longitudinal side ribs centered within each side wall 84. Each side offset includes a top and bottom transition segment 106 extending to a central flat land 108 generally centered on the side wall 84. The side offsets are stiffening structures that increases the overall width of the center sill 70 to 15.313″ (from a conventional width of 13.813″) and the overall density of the center sill 70 is 83.7 lbs/ft with 0.5″ thickness steel. The increased weight is offset by an increased stiffness to the overall center sill 70 of this embodiment. The stiffening structures of this embodiment yields greater than 3% increase in the bounded envelope and an associated increase in resistance to buckling forces.

(24) A third embodiment of the center sill 70 including stiffness enhancing structures of the invention is shown in FIGS. 8A and 8B, with the common features not described in detail again. In this embodiment the top offset is formed across the entire top 82 of the center sill 70 and mimics the shape of a center sill shroud with the transition elements 116 extending from a modified upper curved section 86′ to a top central curved section 114. The upper curved sections 86′ are modified in that each couples a side 84 to the transition elements 116 and not to a perpendicular member as in earlier embodiments. Here the increase in bounded area may be about 5%. The weight of this design with 0.5″ steel is 107.414 lbs/ft. An alternative center sill 70 to this third embodiment is shown in FIG. 8B and the difference is to eliminate the internal flanges 92 and the associated coupling 94 for weight savings, dropping the weight per foot to 103.308 lbs/ft for a 0.5″ thick design:

(25) A fourth embodiment of the cold formed center sill 70 of the present invention is shown in FIG. 9. In the further embodiment the stiffening structure is an offset extending across the entire top 82 as shown including transition elements 116 from modified corners 86′ to the flat central land 98. This center sill 70 further includes a reinforcing plate 120 welded in the interior only adjacent the draft arm ends and extending for a few feet to stop about at the floor intersection.

(26) In all of the center sills 70 of the present invention the top surface of the center sill is above the top surface of the draft arms due to the stiffening offset structure. Conventionally in the prior art center sill structures the top surface of the center sill is aligned with the top surface of the draft arm. The reinforcing plate 100 in the fourth embodiment is aligned with the top surface of the draft arm and can convey forces down to the floor intersection. The stiffening structures of this fourth embodiment yields greater than 2-4% increase in the bounded envelope and an associated increase in resistance to buckling forces.

(27) The above discussion illustrates that the cold formed center sills 70 of the present invention offer significant advantages over the prior art center sills 10, 20 30 or 40 without detrimental drawbacks. It will be apparent to those of ordinary skill in the art that various changes may be made to the present invention without departing from the spirit and scope thereof. Consequently, the present invention is intended to be defined by the appended claims and equivalents thereto.