Concrete form panels with hollow reinforcing ribs

Abstract

A form panel adapted to have a plurality of form panels secured together in edge-to-edge relation to form a group having a planar surface and having one group secured in spaced relation from another group and defining a wall forming chamber therebetween. Each form panel includes a sheet member having a plurality of reinforcing ribs with flanges secured to one surface thereof by a welding process wherein the opposite surface of the sheet is planar and is characterized by an absence of distortion and disfigurement.

Description

In the forming of concrete foundations or other concrete walls, it is desirable to have a plurality of panels that may be connected together. The panels may be in the order of approximately 3 to 4 feet wide and 8 feet high or other suitable dimensions as are required by the particular application and are made of relatively hard and durable material, such as metal, for long life. When the form panels are constructed of cast aluminum or steel of suitable thickness for the strength necessary for a sturdy structure, weight becomes a problem requiring approximately 5.9 pounds per square foot of forms and a number of men to handle each panel in erecting or disassembling the form. Form panels have been constructed of lightweight metal such wrought aluminum, with hollow reinforcing ribs for strength and support. Typical form panel structures are of welded construction and have a tendency to warp during weld assembly and to deflect in the wall due to the pressure of the concrete. However, aluminum form panels have had their disadvantages such as difficulty in an operator grasping portions thereof for holding the form panels during assembly, lack of safety in the operator moving over the oily forms when erected, excessive wear in certain wear-prone areas, such as adjacent to the fasteners, and high cost due to time consuming operations in manufacturing the forms.

The principal objects of the present invention are: to provide a concrete form and panel therefor that substantially eliminates the aforementioned difficulties with prior form panels; to provide a concrete form panel constructed of metal such as aluminum with reinforcing structure that is light in weight, as for example 2.95 pounds per square foot of form which is approximately 50% lighter than typical existing form panels, and that is strong and capable of withstanding rough handling, treatment and pressures of as high as 800 pounds per square foot of pressure of the cementitious material such as concrete or the like that is poured in the form erected from such panels; to provide such a structure which has the component parts thereof joined by a manufacturing process to maintain a planar exposed surface of a sheet member; to provide such a structure wherein the panel is formed of a plate, strips and rib sections which rib sections are particularly adapted to be made by an extrusion process; to provide such a structure facilitating an operator holding the panel by grasping the ribs and that also serve as steps to facilitate an operator moving over the erected forms; to provide such a structure that is manufacturable at high speeds by processes that help to reduce or eliminate warpage in the form panels; to provide such a structure wherein certain widths of panels are adapted to be made by extrusion processes; to provide such a structure wherein the portions of the plates that are in contact with the cementitious material have embossed designs thereon for producing designs on the concrete wall formed thereby; to provide such a form panel adapted for assembly in sequence operations at production stations and in which parts are selectively joined by gun welding; to provide such a structure wherein the form panels have portions for receiving tie-rods or bars and fasteners and wherein wear members are used to prevent excessive wear or abrading of the form panel from the installation and removal of the tie-rods and fasteners; and to provide such a form panel which is economical to manufacture, easily and conveniently handled and that can be quickly erected in abutting edge-to-edge relation to present a substantially uninterrupted plane surface for the concrete poured between the groups of forms.

Other objects and advantages of this invention will become apparent from the following description taken in connection with the accompanying drawings wherein are set forth by way of illustration and example certain embodiments of this invention.

FIG. 1 is a perspective fragmentary view of a concrete form comprising a number of concrete form panels made in accordance with the present invention.

FIG. 2 is an elevational view of a concrete form panel showing the face having reinforcing ribs thereon.

FIG. 3 is an end sectional view through the form panel along the lines 3--3, FIG. 1.

FIG. 4 is an enlarged fragmentary sectional view through the fastener taken along the line 4--4, FIG. 1.

FIG. 5 is an enlarged fragmentary sectional view through the form plate and reinforcing rib taken on the line 5--5, FIG. 2.

FIG. 6 is an enlarged fragmentary sectional view through a bushing plate showing structural details thereof.

FIG. 7 is an elevation view of a form panel illustrating a variation in the reinforcing rib arrangement.

FIG. 8 is an elevation view of a modified form of form panel wherein the form plate is an extruded member.

FIG. 9 is an enlarged end section view of the modified form panel taken along the line 9--9, FIG. 8.

FIG. 10 is an elevation view of a modified form of form panel illustrating a variation in reinforcing rib structure.

FIG. 11 is an end section view of the modified form panel of FIG. 10 taken along the line 11--11, FIG. 10.

FIG. 12 is an enlarged fragmentary sectional view through a form plate and modified form of reinforcing rib.

Referring more in detail to the drawings:

As required, detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention which may be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriate detailed structure.

The reference numeral 1 designates generally a concrete form that is provided by placing a plurality of lightweight form panels 2 in edge-to-edge abutting relation forming panel groups 3 and 4 which are spaced apart and retained in that condition by tie-bars 5 and fastening devices 6 whereby the form walls of the groups are in a condition to receive cementitious material or concrete that may be poured in a space 7 between the form walls to form a concrete wall. The cavity or space 7 is defined by smooth or plane surfaces so that the wall of concrete preferably will have plane outer or exposed faces.

The form panels 2 preferably are formed of a lightweight metal, such as aluminum, and include a plate or sheet 9 cut to the size of the portion of the wall face the panel is to form. As for example, the plate may be in the nature of approximately 8 feet long and 3 or 4 feet wide. However, the plates may be longer to provide a wall of greater height, such as 9 feet for a house foundation, if desired. The plate 9 has opposed surfaces 8 and 10 wherein the surface 8 is preferably a plane surface that forms one surface or side of the concrete retaining cavity 7. The plate 9 has opposed side edges 11 and 12 and end edges 13. In the illustrated structure, the form panel has a flange formed by end strips 14 and 15 with outer surfaces 16 substantially coinciding with the end edges 13 of the plate 9, said strips being welded or otherwise secured to the plate 9 whereby the strips are on edge and project substantially normal to the surface 10. Side strips 17 and 18 extend along the side portions of the plate 9 and are welded or otherwise secured to the plate 9 whereby outer surfaces 19 are spaced inwardly from the edges 11 and 12 approximately one-half the thickness of the tie-bars 5. The strips 17 and 18 are also arranged on edge and project substantially normal to the surface 10 and have their ends abutting and secured to the ends of the end strips 14 and 15, such as by welding for the height thereof, thereby forming a continuous strip or flange arrangement adjacent the periphery of the plate 9.

The panel 2 is provided with a plurality of hollow reinforcing ribs or hat sections 20 that are generally channel shaped and adapted for production by extrusion. The ribs 20 have web portions 21 and leg members 22 extending from said web preferably in diverging relation. The legs 22 preferably curve outwardly and terminate in flanges 23 that extend outwardly from the legs 22 and have surfaces 24 adapted to lie directly on the face 10 of the plate 9. It is to be noted that the exterior corner between the flanges 23 and respective legs 22 is rounded and the exterior surface of the legs and flanges is characterized by an absence of sharp corners for a purpose later described. The flanges 23 are of a substantial width in the nature of 3/4 inch to 11/2 in width and have a free edge spaced from the respective leg 22 and extends longitudinally along the length of the rib 20. In ordinary foundation forms, it is preferred that the strips 14, 15, 17 and 18 be of a width in the nature of 2 inches and also that the ribs 20 have a similar dimension with an outer face 25 of the webs 21 spaced from the surface 10 a distance equal to or less than the width of the strips 14, 15, 17 and 18.

The ribs 20 each have a plurality of serrations 26 on the legs 22 wherein the serrations 26 extend longitudinally of the ribs 20 for the length thereof forming a non-skid surface with the serrated portion in the nature of one-half to three-fourths of an inch in width. As illustrated, there are a plurality of transversely disposed ribs 20 arranged in parallel relation whereby they extend horizontally when the form is in an erected position. Each of the ribs 20 preferably extends to and has abutting engagement with the side strips 17 and 18 and are welded or otherwise secured thereto whereby the ribs reinforce the plate 9 and also the side strips 17 and 18 to maintain the shape of the panel and the flatness of the plate 9. To further reinforce the plate 9 and the end strips 14 and 15, ribs or hat sections 28 similar to the ribs 20 are arranged between the end strips and the outermost ribs 20 and are secured to the plate 9. The ribs 28 have their flanges adapted to lie directly on the surface 10. Ends 29 of the ribs 28 abut the end strips 14 and 15 and the outermost ribs 20 and are preferably welded or otherwise secured thereto.

The ribs 20 and 28 are arranged relative to one another and the plate 9 whereby manufacture of the panel 2 can be accomplished by high speed construction methods. The ribs 20 and 28 are positioned and secured only as necessary to retain the position for movement to the station for positive fastening, the preliminary securing preferably being by minimal tack welding. The illustrated structure is adapted to have the fastening of parts together by an automatic or semi-automatic gun welding process. During assembly it is desirable to induce a prebow in the panel 2 wherein the surface 8 is preferably convex so that under load conditions it will deflect to a flat or planar condition so as to permit higher loads without excessive deflection. Prebow can be induced by any suitable method, one method being to induce deflection in the plate 9 and restraining it in that position against a copper plate contact member (not shown), which provides electric circuit contact with the plate 9 for welding, and welding the ribs thereon while deflected. The form panel as shown for residential use are typically 3 foot by 8 foot and will stand up to 800 pounds per square foot of concrete pressure during use without excessive deflection. The strips 14, 15, 17 and 18 are secured to the plate 9 after which the ribs 20 and 28 are placed and suitably held in position such as by tack welding, after which the form panel 2 is placed in a gun welding apparatus (not shown) having a plurality of spaced gun welders which can be individually and selectively moved or moved in groups into position on the flanges 23 of the ribs 20 and 28 and sequentially fired to weld same to the plate 9 wherein the welds 30 are positioned between the outermost edges of the flanges 23 and the legs 22 and join portions of the surfaces 24 to portions of the surface 10. Gun welding comprises the use of a single electrode moved into engagement with the flange 23 over the area of the weld wherein an electric circuit is completed wherein the weld flashes and blows the sheet metal up and welding rod or wire is fed into the cavity and the weld 30 is formed between the contacting surfaces of the plate 9 and flange 23. Gun welding results in a substantially distortion free form panel 2 and a surface 10 which is characterized by an absence of welding marks and disfigurement. The welds 30 are in the nature of three-quarters of an inch in diameter. It is to be noted that resistance or spot welding can also be used in place of the gun-welding as long as the surface 10 is characterized by an absence of welding marks and disfigurement.

Gun welding can be one of two different kinds, one of which is a non-penetrating weld which is as illustrated and the other being a penetrating weld. In gun welding a welding rod or wire is fed into the molten weld area to provide fill material and in the non-penetrating weld the weld does not go completely through the work material. In the penetrating type of weld, the weld goes through the work material and in the work material shown the welding rod would go through the plate 9 and leave a tip projecting therefrom which is suitably shaved or otherwise removed by a shaving or milling machine (not shown) to leave a surface 10 which is characterized by an absence of welding marks and disfigurement. Preferably gun welds are used for assembly and as formed have a shear strength of between 500 psi per weld and 1500 psi per weld depending on the type of welding wire used and the type of gun weld used.

During manufacture, the form panels 2 are incrementally moved through the gun-welding apparatus in spaced intervals whereby the gun-welders are positioned so that the welds 30 on the ribs 20 and the welds on the ribs 28 are in line, the lines being generally longitudinal of the form panels 2 and spaced in the nature of three to four inches apart. The ends of the ribs 28 and 20 preferably are welded or otherwise secured to the respective strips 14, 15, 17 and 18 and the strips 14, 15, 17 and 18 are welded to the plate 9 in a conventional manner. The strength of the joined ends of the strips 14, 15, 17 and 18 is increased by securing gusset members 31 in the corners preferably welding same for the length of edges thereof to the adjacent strips and the plate 9. The gussets reduce maintenance by preventing damage to the corners during use due to the increased strength of the corners. The hollow construction of the ribs 20 and 28 assures lightness in weight and great strength as well as support for the plate 9 and the serrations 26 facilitate an operator obtaining a grip on the ribs whereby the panels 2 may be easily handled and maneuvered into position.

The side peripheral edges 11 and 12 of the plate 9 are milled or otherwise cut to form notches 34 at each location along the side edges where a tie-bar 5 may be utilized in fastening the groups 3 and 4 together. In the illustrated structure, there are four notches 34 on each side of the form panel 2 and the notches are arranged symmetrically whereby they will register with notches 34 of an adjacent panel 2 in either the position illustrated or when the form panels are inverted. When adjacent panels are in edge-to-edge or abutting relation, the notches 34 cooperate to form an opening through the plates 9 through which the tie-bars 5 can extend. As is the custom, each tie-bar 5 is provided with an opening 35 and when the tie-bars are between the adjacent side strips, the fasteners 6 extend through the openings 35 and also through openings 36 of the side strips 17 and 18.

In the structure illustrated, the fastening members 6 are each in the form of a pin 37 having a head 38 at one end and a slot 39 in the shank spaced from the head and adapted to receive a key or wedge 40 so arranged that when the wedge is driven into the slot 39, the wedge 40 and the head 38 will clamp the side portions of the adjacent form panels to secure same together and also anchor the tie-bars 5 therebetween. The pins and wedges preferably are of steel and to prevent excessive wear or abrading of the side strips 17 and 18 and enlarging the holes 36, bushing members or plates 41 of hard and durable material such as steel are mounted adjacent the openings 36. In the illustrated structure, the plates 41 each have a bore 42 therethrough and lateral flange portions 43 extending outwardly from the bores 42. Preferably, each plate 41 is punched and upset to form the bore 42 and a flange 44 around the bore 42 wherein the bore 42 is elongate. The bores 42 are sized to receive the pins 37 therethrough with a minimum of clearance therebetween and still allowing easy movement of the pins 37 in the bores 42. As illustrated, the flange 44 is received in a respective bore 36 having the remote end terminating at the outermost disposed surface of the side strips 17 and 18. The flange 44 permits greater surface area contact between the pins 37 and the plates 41. The plates 41 are suitably secured to the side strips 17 and 18 and as illustrated, are secured by rivets 45 extending through the respective side strips 17 or 18 and the lateral flanges 43. It is preferred that the form panels have wear or striker plates adjacent the fasteners 6 to prevent damage to and distorting or marring of the surface 8 during installation and removal of the fasteners 6. As illustrated, wear plates 46 are secured to the surface 10 adjacent the fasteners 6 providing rigid long wearing plates that protect the plate 9 from impact by a hammer or the like used in setting or removing the wedge keys 40. The wear plates 46 may be secured to the plates 9 in any suitable manner such as by welding and preferably are gun-welded to the surface 10, with the welds preferably being positioned between the peripheral edges of the wear plates 46, to prevent warpage of the plate 9.

In operation, the panels 2 are coated with an oil or release agent to prevent the adhesion of concrete thereto. Also, the ribs 20 and 28 are characterized by an absence of exposed sharp corners and the legs are curved to facilitate self-cleaning or shedding of concrete during use. In erecting a form of the form panels 2, the panels 2 may be easily picked up and held by the serrated portions 26, moved into position and held there while the tie-bars 5 are positioned and the pins 37 inserted into the openings 42 of the bushings 41 and the wedge keys 40 mounted in the slot 39. The wedge keys 40 are then driven into place to tightly clamp the adjacent form panels 2 in edge-to-edge abutting relation whereby the edges 11 and 12 abut the plate side edges of an adjacent form panel 2. When a concrete form is completely erected, the operator may climb over the forms as by using the ribs 20 as steps and hand holds, with the serrations 26 providing slip resistant engagement, thereby facilitating safer movement of the operators around the forms.

FIG. 7 illustrates a modified form of the form panel 2 that is designated generally by the reference numeral 48 and is similar in construction, method of manufacture, operation and method of assembly as the form panel 2 but has a variation in the arrangement of the reinforcing ribs 20 and 28. Like numbers designate like or similar parts or structure of the form panels 2 and 48. The form panel 48 includes the ribs 28 and also includes, in the illustrated form, three groups of two each of the ribs 20 with the ribs 20 and 28 being secured to the plate 9 of the form panel 48 as they are in the form panel 2. In the particular form illustrated in FIG. 7, the form panel 48 includes hollow rib or hat sections 49 that are similar in construction to the ribs 20 and 28 with each having a web 21 and flanges or leg members 22 extending from the web 21 preferably in diverging relation with the legs 22 terminating in flanges 23 that extend outwardly from the legs 21 and along the longitudinal edges thereof. The ribs 49 are adapted to lie on the surface 10 and be secured to the plate 9 in a manner similar to the securing of the ribs 20 and 28, that is, by a gun welding process.

Preferably, the ends of the ribs 49 are cut or otherwise formed so as to be adapted to abut the adjacent ribs 20 and to be secured thereto in any conventional manner, such as by welding. As illustrated, the ribs 49 extend between each of two sets of the ribs 20 and preferably are positioned in line with the ribs 28 so as to facilitate manufacture of the form panels 48 by an automatic or semi-automatic gun welding process as are the form panels 2. The ribs 49 provide increased rigidity or strength longitudinally along the form panel 48 and help prevent buckling or bowing thereof when subjected to the pressure of the cementitious composition when it is poured between groups of form panels. The ribs 49 are positioned in such a manner so as to not interfere with the use of the form panel 48 when it is in use in wall forming sections.

FIGS. 8 and 9 inclusive illustrate a modified form of form panel designated by the reference numeral 55 and is similar in construction, method of manufacture, operation and method of assembly as the form panel 2 illustrated in FIGS. 1-6 inclusive wherein like numbers designate like or similar parts or structure. The form panel 55 as illustrated in FIG. 8 differs from the form panels 2 in that the side strips 17 and 18 are integral with the plate 9 whereby the plate 9 and side strips 17 and 18 are adapted to be manufactured in an integral structure by an extrusion process. The form panel 55 is particularly adapted for form panels of narrower widths than the form panel 2, as for example in the nature of a width of 1 foot. As illustrated, the form panel 55 has the reinforcing ribs 20 secured to the surface 10 of the plate 9 as described above and because of the narrow width, the ribs 28 are absent.

FIGS. 10 and 11 illustrate another modified form panel that is designated generally by the reference numeral 65 that is similar in method of manufacture, operation and method of assembly as the form shown in FIGS. 1-6 inclusive. Like numbers on the form panels 2 and 65 designate similar or like parts or structure. The form panel 65 has a hollow rib or hat structure 67 which is generally centrally located between the side edges 11 and 12 of the plate 9 and extends longitudinally along the length thereof having the ribs 20 secured to and extending between opposite sides of the rib 67 and the side strips 17 and 18 as illustrated, the rib 67 is of a rib within a rib type structure and includes an outer hollow rib 68 and an inner hollow rib 69 both preferably secured to the surface 10. The rib 68 has a web portion 71 and legs or flange portions 72 extending therefrom preferably in diverging relation terminating in flanges 73 that are adapted to lie directly on the surface 10. The flanges 73 extend outwardly of their respective legs 72 and extend longitudinally along the length of the rib 68. The rib 69 is comprised of a web 75 having legs or flanges 76 extending therefrom preferably in diverging relation and terminating in flanges 77 that extend outwardly of the legs 76 and longitudinally along the length of the rib 69. The web 75 is adapted to lie directly on the surface 10 and the flanges 77 are adapted to lie directly on an inner disposed surface 79 of the web 71. Opposite ends of the ribs 68 and 69 preferably are secured to the end strips 14 and 15 such as by welding, to secure same in abutting relation.

In manufacturing the form panel 65, the end strips 14 and 15 and the side strips 17 and 18 are secured to the surface 10 such as by welding. The rib 69 is then placed on the surface 10 and held in position such as by tack welding and then gun welded or can be gun welded initially whereby the web 75 is secured to the surface 10 of the panel 9. The rib 68 is then placed in overlying relation to the rib 69 whereby surfaces 80 of the flanges 77 are in engagement with the surface 79 of the web 71 and surfaces 81 are in engagement with the surface 10. The ribs 68 and 20 are held in the desired position such as by tack welding. The gun welders are then used to weld the rib 68 and the ribs 20 to the surface 10 and the flanges 77. The locations of the welds on the ribs and the plate 9 are preferably positioned in lines longitudinally along the form panel 65 so that the form panel 65 can be moved through a gun welding apparatus (not shown) for automatic or semi-automatic welding thereof. As described above, the welds made by the gun welders are spaced between the outer edges of the flanges and their respective legs and are positioned at intervals along the flanges 73, 80 and 23. The gun welders join the flanges 77 to the web 71 as at 83 and the flanges 73 are welded on the surface 10 as at 84 to form a rigid and lightweight form panel. The welds 83, 84 and 30 are spaced at intervals in the nature of three to four inches.

FIG. 12 illustrates a modified form of hollow reinforcing rib designated by the numeral 90 and is similar to the rib 20. The rib 90 has a web 91 and legs 92 extending from the web preferably in diverging relation. The legs 92 terminate in flanges 93 which extend outwardly from the legs 92 and have surfaces 94 adapted to lie directly on the face 10 of the plate 9 and be secured thereto by welds 30, such as gun welds. The major difference between the rib 90 and the rib 20 is that the interior surface of the legs 92 are each provided with a pair of spaced apart ribs 95 and 96 with each of the pairs extending longitudinally along the length of the rib 90. The ribs 95 and 96 form a groove 97 therebetween with each of the grooves 97 opening generally toward the opposite leg 92 and are positioned adjacent to flanges 93. A plate member 98 has edge portions receivable in each of the grooves 97 thereby mounting same on the rib 90 wherein the plate 98 has a surface 99 in spaced relation to the face 10 and generally parallel thereto. The plate 98 provides a seal which prevents the entry of foreign material into a major portion of the interior of the rib 90 when same is secured to the plate 9. The plate 98 can be of a material having a low thermal conductivity and thereby providing insulation for the plate 9 for a purpose to be later described.

In use of the form panels 2, 48, 55 and 65, it is desirable under certain cold weather conditions to provide insulation for the concrete poured between the panel groups 3 and 4 to prevent the concrete from freezing before it sets. In this regard the form panels can be provided with a coating (not shown) of insulating foam such as urethane or other suitable insulating material on the face 10. The insulation will help retard heat loss from the concrete while it is setting. The insulating material can be sprayed on otherwise applied to the exposed portions of the face 10 wherein a substantial amount of area would be uninsulated under the re-enforcing ribs. The plate 98 as described above, can provide insulation for the areas of the surface 10 under the ribs 90.

Use, assembly and disassembly of the form panels 48, 55 and 65 are similar to that of the form panel 2 and all may be prebowed similar to the form panel 2. An oil or release agent can be used to coat the panels 2, 48, 55 and 65 to prevent the adhesion of concrete thereto and the respective reinforcing ribs are characterized by an absence of exposed sharp or square corners to help shed the concrete and prevent buildup. It is also to be noted that the surfaces 8 of the form panels 2, 48, 55 and 65 may have designs embossed thereon to form decorative finishes on the concrete wall that is formed between the groups 3 and 4 of the form panels. As for example, such decorations would typically include embossed designs that form a brick-like appearance on a concrete wall.

It is to be understood that while I have illustrated and described certain forms of my invention, it is not to be limited to the specific form or arrangement of parts herein described and shown.

Claims

What I claim is:

1. A panel for forming a concrete wall comprising:

a. a plate having a pair of opposed planar side faces, said plate having opposed side edges and opposed end edges with the end edges substantially transverse to said side edges, one of said opposed side faces presenting a planar surface for forming one surface of a concrete wall;

b. said plate having side strips adjacent to and spaced from a respective side edge forming side flanges, said side strips extending from and being substantially normal to the other opposed side face and having opposite ends adjacent said end edges;

c. said plate having end strips adjacent to respective end edges, said end strips extending from and being substantially normal to said other opposed side face and having opposite ends adjacent respective ends of said side strips;

d. a plurality of hollow reinforcing ribs secured to the other opposed side face, said hollow ribs being generally channel shaped with a web and side legs extending from opposite longitudinal edges thereof terminating in outwardly extending flanges having free edges spaced from a respective leg and having surfaces which lie on portions of said other opposed side face, and gun welds securing said rib flanges to said plate with portions of the engaging flange surfaces and other opposed side face joined together, said flanges being greater in width than the width of the gun welds, said welds being positioned generally centrally between a leg and said flange free edge;

e. a plurality of said ribs extending transversely of the longitudinal dimension of said plate in spaced apart parallel relation with said ribs having opposite ends abutting said side strips and being secured thereto;

f. the gun welds securing said rib flanges to the plate being in mutually spaced apart relation in lines extending both transversely and longitudinally of said plate and characterized by an absence of warpage in said plate and disfigurement of said one opposed side face;

g. said rib legs having inwardly facing longitudinal grooves therein adjacent said other opposed side face, an elongate flat strip member positioned in the interior of said ribs and having opposed side edges seated in said grooves, said flat strip members extending the length of the respective rib for preventing entry of foreign material into a major portion of the space defined by said ribs and said plate.

2. The panel as set forth in claim 1 including:

a. a plurality of said reinforcing ribs extending transversely to said first named reinforcing ribs,

b. the gun welds securing said last named ribs being positioned in the aforesaid pattern.

3. The panel as set forth in claim 1 including:

a. a plurality of serrations on the outer surfaces of said legs forming a non-skid surface.