Patent Application
20050117969
The present invention generally relates to steps and more particularly to steps for heavy duty motor vehicles, such as industrial trucks, to facilitate the ingress and egress of operators to and from cabs of the trucks.
Truck steps are conventionally constructed from metal plates having planar support surfaces. Grip structures are typically formed in the support surface to prevent slippage, especially when the step is wet or covered with ice. Drainage holes may also be formed in the metal plate to allow water to drain from the support surface. The grip structures are disposed around openings in the plate and usually have curved side walls defining continuous top rims. While grip structures of this construction will improve the grip of a step, the continuous nature of the top rims can still render the top rims and, thus, the step quite slippery when the step is wet or covered with ice. In order to address this deficiency of conventional grip structures, other grip structures have been developed. Such grip structures are disclosed in U.S. Pat. No. 3,181,440 to Mullaney et al. and U.S. Pat. No. 4,343,119 to Bahnfleth.
The rosette of the Bahnfleth patent includes a plurality of spaced-apart extensions having arcuate edges. The extensions slope inwardly to provide the rosette with a relatively narrow cross-shaped opening. Although contact portions of the rosette edges are discontinuous in a plane of contact, these contact portions are small. Moreover, the slope of the extensions present major surfaces that are located just below the contact portions. These major surfaces can become slippery when the rosette is wet or covered with ice. Moreover, the narrowness of the opening in the rosette can make the rosette susceptible to clogging with dirt or ice.
The grip structures of the Mullaney et al. patent comprise cylindrical flanges that extend upright from a metal tread plate 14. Top portions of the flanges are gulleted to provide a number of fairly deep truncated gripping edges. In order to increase the height of the flanges and permit the flanges to extend upright, the flanges are thinned. With the foregoing high-profile construction, the flanges may trap footwear and cause injury if they are not properly spaced apart. For this reason, the Mullaney et al. patent discloses that the flanges must be spaced closely together. Such close spacing, however, may not always be desirable.
Based on the foregoing, there is a need in the art for an improved anti-slip step having low profile grip structures. The present invention is directed to such an anti-slip step.
In accordance with the present invention, an anti-slip step for a motor vehicle is provided. The step includes a tread plate with a top surface and a bottom surface. A plurality of grip structures extend upwardly from the top surface of the tread plate. Each of the grip structures at least partially defines a hole extending through the tread plate. Each of the grip structures includes a base having a continuous, curved side wall that is joined to the tread plate. A plurality of spaced-apart tabs are joined to the base and extend upwardly therefrom. A plurality of drain structures extend downwardly from the bottom surface of the tread plate. Each of the drain structures at least partially defines a drain hole extending through the tread plate.
In accordance with another feature of the present invention each of the grip structures has a height (H) and the side wall of the base is joined to the tread plate so as to form a radius of curvature (RC) between the base and the top surface of the tread plate, wherein the ratio of the radius of curvature (RC) to the height (H) of the grip structure is greater than 0.5.
Also provided in accordance with the present invention is a method of forming an anti-slip step. Pursuant to the method, a tread plate is provided having top and bottom surfaces. A plurality of holes are formed in the tread plate. For at least one of the holes, a boundary region of the tread plate disposed around the hole is bent so as to extend out of the plane of the top surface and thereby form a first structure at least partially defining a first opening. For at least another one of the holes, a boundary region disposed around the hole is bent so as to extend out of the plane of the top surface and thereby form a second structure at least partially defining a second opening, wherein the second structure extends a farther distance from the tread plate than the first structure.
The features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:
It should be noted that in the detailed description that follows, identical components have the same reference numerals, regardless of whether they are shown in different embodiments of the present invention. It should also be noted that in order to clearly and concisely disclose the present invention, the drawings may not necessarily be to scale and certain features of the invention may be shown in somewhat schematic form.
Referring now to
A plurality of grip structures 32 and drain structures 34 extend from the tread plate 14 and at least partially define a plurality of grip openings 36 and drain openings 38 in the tread plate 14, respectively. The grip structures 32 extend upwardly from the top surface 22 of the tread plate 14, while the drain structures 34 extend downwardly from the bottom surface 24 of the tread plate 14. The grip structures 32 provide non-continuous gripping to footwear brought into contact with the tread plate 14, while the drain structures 34 facilitate the drainage of water from the top surface 22 of the tread plate 14 so as to prevent the pooling of water thereon.
Preferably, the grip structures 32 and the drain structures 34 are arranged such that the tread plate 14 has alternating longitudinally-extending rows of grip structures 32 and drain structures 34. In the specific version of the invention disclosed in
Referring now to
In each grip structure 32, the base is joined to the top surface of the tread plate 14 so as to form a radius of curvature RC1 between the base and the top surface, wherein the ratio of the radius of curvature RC1 to the height H1 of the grip structure (i.e., RC1/H) is greater than 0.5, more preferably greater than 0.75, still more preferably greater than 1. In addition, each grip structure is constructed such that the ratio of the height H of the grip structure to the diameter D1 of the grip opening of the grip structure (i.e., H/D1) is less than 0.75, more preferably less than 0.5, still more preferably less than 0.3. Furthermore, the ratio of the height H of each grip structure 32 to the thickness “T” of the tread plate 14 (i.e., H/T) is preferably less than 3, more preferably less than 2. With the IS foregoing structure, the grip structures 32 have low profiles that do not require the grip structures 32 to be disposed closely together.
Referring now to
In each drain structure 34, each tab 46 is joined to the bottom surface 24 of the tread plate 14 so as to form a radius of curvature RC2 between the tab 46 and the bottom surface 24, wherein the ratio of the radius of curvature RC2 to the depth Dp of the drain structure 34 (i.e., RC2/Dp) is greater than 1, more preferably greater than 2, still more preferably greater than 3. Preferably, the radius of curvature RC2 of the drain structures 34 is at least substantially the same as the radius of curvature RC1 of the grip structures 32.
The diameter D2 of the drain openings 38 of the drain structures 34 is preferably at least substantially the same as the diameter D1 of the grip openings 36 of the grip structures 32. The depth Dp of the drain structures 34, however, is preferably less than the height H of the grip structures 32. Still more preferably, the ratio of the depth Dp of the drain structures 34 to the height H of the grip structures 32 (Dp/H) is less than 1, more preferably less than 0.75, still more preferably less than 0.5.
In lieu of having the construction described above, the drain structures 34 may have the same structure (with the same dimensions) as the grip structures 32 (except for extending downwardly from the bottom surface 24), wherein the tabs 46 are joined to bases joined to the bottom surface 24.
Preferably, each of the grip structures 32 and each of the drain structures 34 is formed using a punching operation and an embossing operation, wherein in the punching operation, a hole is formed in the tread plate 14, and in the embossing operation, a boundary region of the tread plate 14 around the hole is pushed away from the tread plate 14 so as to extend out of the plane of the tread plate 14, i.e., so as to extend out of the plane of the top surface 22 or the bottom surface 24, as the case may be. The holes for forming the drain structures 34 are similar to the holes for forming the grip structures 32, except the holes for forming the drain structures 34 are about 13% larger than the holes for the grip structures 32 and except for the difference noted below. In another embodiment of the present invention, all of the holes for the grip structures 32 and the drain structures 34 have the same size and configuration.
One of the holes for the grip structures 32, designated with the reference numeral 50, is shown in
One of the holes for the drain structures 34, designated with the reference numeral 62, is shown in
Once the holes 50, 62 are formed in the tread plate 14, the boundary regions 58, 70 of the tread plate 14 around the holes 50, 62 are contacted by embossing dies on a press and pushed upwardly or downwardly (depending on the arrangement of the press and the support structure 12) to form the grip structures 32 and the drain structures 34. With regard to the hole 50 for a grip structure 32, the boundary region 58 extends radially outward from the second edges 56 to form an annular portion between the second edges 56 and the outer perimeter 60 of the boundary region 58. With regard to the hole 62 for a drain structure 34, the boundary region 70 has a radius about equal to the distance of the second edges 68 from the center of the hole 62. The boundary regions 58 for the holes 50 are determined by the radii of the dies for the grip structures 32, and the boundary regions 70 for the holes 62 are determined by the radii of the dies for the drain structures 34. The dies for the grip structures 32 have larger radii than the dies for the drain structures 34.
When the dies for the drain structures 34 are aligned with the holes 62 and pressed against the tread plate 14, the dies for the drain structures 34 only contact the tabs 64 and bend them to form the tabs 46 for the drain structures 34, whereas when the dies for the grip structures 32 are aligned with the holes 50 and pressed against the tread plate 14, the dies for the grip structures 32 contact the annular portions of the tread plate 14 disposed radially outward from the second edges 56 and bend them to form the bases 40 for the grip structures 32.
From the foregoing description, it should be appreciated that the step 10 of the present invention is simple to produce, has improved anti-slip features and facilitates the drainage of water from the step 10. The low profile of the grip structures 32 permits the grip structures 32 to be more spread out without increasing the risk of trapping footwear.
While the step 10 is especially adapted for use on an industrial truck having an elevated cab, the step 10 can also be used in other applications, such as on ships, locomotives and on fixed structures, such as elevated industrial walkways.
While the invention has been shown and described with respect to particular embodiments thereof, those embodiments are for the purpose of illustration rather than limitation, and other variations and modifications of the specific embodiments herein described will be apparent to those skilled in the art, all within the intended spirit and scope of the invention. Accordingly, the invention is not to be limited in scope and effect to the specific embodiments herein described, nor in any other way that is inconsistent with the extent to which the progress in the art has been advanced by the invention.
