Patent Publication Number: US-6908256-B1

Title: Drainage grate assembly

Description:
BACKGROUND OF THE INVENTION 
   The present invention relates to drainage grates used in connection with trench drains and the like for the drainage of surface water. Trench drains and similar drainage structures are used in a variety of environments, such as walkways, bike and foot paths, outdoor malls, parking lots, airport tarmacs and other traffic environments which require the drainage of surface water. Trench drains and drainage structures generally are known in the art as described in, for example, U.S. Pat. Nos. 4,630,966; 4,699,544; 5,462,382 and 4,553,874, incorporated herein by reference. In order to provide access of surface water to the drainage structure, while at the same time enabling practical movement of traffic across the structure, apertured drainage grates are typically employed to provide a substantially continuous surface over which pedestrian or vehicle traffic can freely move. 
   Drainage grates are typically made of varying gauges of sheet metal and are, therefore, subject to damage. Dents, buckles and perforations in the drainage grate are not only aesthetically undesirable, but are also safety concerns which can lead to injury to pedestrians and damage to surface vehicles. Accordingly, drainage grates must meet particular load ratings depending upon the environment in which they are to be used. Although there is no universal system for load rating of trench drains, the internationally recognized DIN 19580 standard, incorporated herein by reference, provides a good basis on which to distinguish between classes. Basically, for trench drains under 8 inches wide, a class A rating will withstand 15 psi within the standard 3 inch by 10 inch load footprint, and is typically used in residential and light pedestrian areas. A class B rating will withstand 140 psi in the load footprint, and is typically used for sidewalks and small private parking lots. A class C rating will withstand 280 psi in the load footprint and is appropriate for commercial parking lots and the like. Classes D and above will withstand 450 psi or more in the load footprint and are found in roads or other areas experiencing heavy wheel loads. 
   The requirement for different load ratings typically means that a manufacturer must provide different grates for different applications. Thus, in practicality, a manufacturer must provide grates of different gauges and materials or which include various reinforcements appended thereto. However, there are practical limits to the gauges of metal which can be used and, even when various reinforcements are included, they often do not provide support to all or most of the vulnerable portions of the drainage grate surface. Thus, even a reinforced grate is still subject to damage in those regions which are not directly reinforced. 
   In view of the foregoing shortcomings, the present invention advantageously provides a reinforced drainage grate which is capable of providing support to all or most of the drainage grate surface, and which can provide a wide range of load ratings without having to manufacture and inventory different grates for each desired load rating. 
   SUMMARY OF THE INVENTION 
   In accordance with the invention there is provided an improved drainage grate assembly which provides improved reinforcement and enables the use of varying gauges of sheet metal where other, more durable and costly materials such as cast iron might otherwise be required. Moreover, the instant invention is advantageously capable of providing substantially continuous support and reinforcement to the entire drainage grate. 
   Accordingly, in one embodiment of the invention there is provided a reinforced drainage grate assembly comprising an elongate drainage grate having a substantially planar drainage surface including a plurality of apertures therethrough and a pair of longitudinally extending side portions, each side portion extending orthogonally below an underside of said drainage surface and including a bottom flange extending toward the opposing one of said side portions. The drainage grate assembly further includes a first reinforcement retaining rail disposed between a first of the bottom flanges and the underside of the drainage surface adjacent a first of said side portions, and a second reinforcement retaining rail disposed between the other of the bottom flanges and the underside of the drainage surface adjacent the opposing said side portion. Each retaining rail is an elongate member which, when assembled, comprises a back surface adjacent a side portion, a bottom surface adjacent a bottom flange, a top surface adjacent the underside of the drainage surface, and a front surface facing the opposing retaining rail. Further, each front surface includes a plurality of slots adapted to receive an end of a reinforcing strip, whereby when opposing ends of a reinforcing strip are disposed within slots in opposing retaining rails, the upper edge of the reinforcing strip abuts at least a portion of the underside of the drainage surface. 
   In carrying out the invention the assembly preferably includes a plurality of reinforcing strips having opposed ends disposed within the slots in the opposed retaining rails. More preferably, the slots comprise a recess disposed in the front surface and extending through said bottom surface. More preferably still, a portion of the upper surface adjacent the slots includes an aperture extending from the upper surface into the slot which is adapted to receive a portion of an upper edge of a reinforcing strip therein, whereby the portion of the upper edge abuts the underside of the drainage surface when the reinforcing strip is disposed in the slot so as to provide metal-to-metal contact therewith. 
   In other aspects of the invention, the assembly includes reinforcing strips having at least two different configurations. In a preferred embodiment, the assembly includes reinforcing strips that are a substantially flat strip of sheet metal and reinforcing strips that are shaped to form a substantially sinusoidal configuration when viewed on edge. 
   In a further aspect of the invention the assembly includes an elongate fastening member secured between the retaining rails and oriented substantially orthogonally from the underside of the drainage surface. The elongate fastening member includes an enlarged distal end portion adapted to cooperate with a receiving member in the drainage channel and secure the drainage grate assembly thereto. In a preferred embodiment, the elongate fastening member includes an upper portion adjacent the underside of the drainage surface which is secured between the retaining rails by abutment of the upper portion against upper edge portions of at least one of the reinforcing strips. 
   A greater understanding of these and other aspects of the invention will be had from the following detailed description and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIGS. 1A and 1B  are perspective views of a drainage grate assembly according to the invention. 
       FIGS. 2A and 2B  are perspective views of segments of a retaining rail for use in a reinforcing assembly according to the invention. 
       FIGS. 3A–3C  are perspective views of various reinforcing strips for use in a reinforcing assembly according to the invention. 
       FIGS. 4A–4C  are various drainage grate configurations for use in accordance with the present invention. 
       FIG. 5  is an exploded view of a fastening mechanism suitable for use in connection with a drainage grate assembly according to the invention. 
       FIG. 6  is a perspective view of a portion of a fastening mechanism suitable for use in connection with a drainage grate assembly according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   As seen with reference to the drawings, the preferred drainage grate assembly of the invention comprises an outer drainage grate, shown generally at  1 , a pair of retaining rails  20  and a plurality of reinforcing strips  30 . As discussed in more detail below, the retaining rails  20  and reinforcing strips, when assembled, cooperate to form a reinforcing assembly, shown generally at  40 . 
   As seen most clearly with reference to  FIGS. 1A ,  1 B and  4 A– 4 C, the drainage grate  1  is formed of sheet metal having a generally planar upper drainage surface  3 , and a pair of opposed side portions  5  extending orthogonally below the drainage surface  3 . In each case the side portions  5  include a lower flange portion  7  extending orthogonally, preferably perpendicularly, from the side portion toward the other of said side portions  5 . As shown, the flange portions  7  extend continuously along the length of said side portions  5 . However, as would be apparent to those of ordinary skill in the art in view of the instant disclosure, the flange portions  7  can be discontinuous, whereby a series of flange portions  7  can be disposed along the length of side portions  5 , so long as they provide support for and cooperate to retain the retaining rails  20  between said flange portions  7  and the lower surface  9  of said drainage grate. As seen in  FIGS. 1A and 4A , and as would be apparent to those of ordinary skill in the art, the upper surface of drainage grates according to the invention can optionally include raised ribs or nobs  6  where improved traction is desired. 
   Typical metal gauges suitable for use in the manufacture of drainage grates according to the invention will be on the order of 3 millimeters or less, and more preferably 2 millimeters or less. The particular type of sheet metal used will depend upon application and aesthetic requirements, although sheet steel is generally preferred. The particular gauge used will depend upon various factors including cost and grate width, with wider grates generally requiring thicker gauges. Of course, the reinforcing strips of the present invention advantageously enable the use of thinner and hence less costly gauges. Selection of suitable materials will be within the level of ordinary skill in the art in view of the instant disclosure. Likewise, the stamping, rolling and bending processes used to fashion the drainage grates according to the invention are also well within the skill in the art. Accordingly, as will be apparent to those of ordinary skill in the art reading the instant disclosure, any standard metal shaping technique known in the art will be suitable for making and shaping the drainage grates according to the instant invention. 
   As seen in  FIG. 1A  and  FIGS. 4A–4C , the drainage surface  3  of drainage grate  1  includes a plurality of apertures  11  for the passage of fluids from the surface of the drainage grate to the drainage structure, such as a trench drain [not shown]. The particular size, shape and pattern of apertures  11  is largely a matter of choice, so long as they function within the intended use environment to permit passage of fluids from the surface of the drainage grate. For example, in use environments where pedestrian traffic is not anticipated, but water removal requirements are high, then larger and/or more numerous apertures are needed. By contrast, in use environments where pedestrian traffic is high, smaller apertures are necessary in order to avoid potential injury associated with high heels and the like. Some preferred patterns according to the invention are shown in  FIGS. 4A–4C . In preferred embodiments, the apertures  11  are arrayed in generally orthogonal, and preferably substantially perpendicular, lines with respect to the side portions  5 . This maximizes the ability and simplicity with which the reinforcing strips  30 ,  130 ,  230  can provide support to the non-apertured portions of the drainage grate. Selection of any particular aperture design for any particular use environment within the scope of the instant invention will be within the level of skill in the art in view of the instant disclosure. 
   As seen best in  FIGS. 1A and 1B , the drainage grate assembly of the invention further includes a reinforcing assembly  40 , which comprises a pair of retaining rails  20 , best seen in  FIGS. 2A and 2B , and a plurality of reinforcing strips  30 . As shown in  FIGS. 2A and 2B , the retaining rails  20  are essentially elongate members dimensioned so as to fit between the bottom surface  9  of the drainage grate  1  and an inner surface of flange portions  7 . Each retaining rail  20  has a back surface  21  which, when assembled into assembly  40 , is disposed adjacent an inner surface of a side portion  5 , a bottom surface  22  which is disposed adjacent an inner surface of a flange portion  7 , a top surface  23  which, when assembled, is disposed adjacent the bottom surface  9  of the drainage grate, and a front surface  24  which, when assembled, faces the opposing retaining rail. It will be apparent to those of ordinary skill in the art that the use of directionally relative terms such as top and bottom herein are intended merely to refer to the relative disposition of elements in their use environment for purposes of clarity and simplicity only, and are not intended to limit the invention in this regard. Likewise, as will be apparent to those of ordinary skill in the art, the overall dimensions such as size and length of the retaining rails can vary depending upon the particular drainage grate dimensions with which it will be employed. 
   Each retaining rail  20  further includes a plurality of slots  25  for receiving an end portion of a reinforcing strip  30 . In the preferred embodiments, the slots  25  comprise recesses or grooves disposed in the front surface  24  and extending through the bottom surface  22 , best seen in  FIGS. 2A and 2B . This configuration advantageously facilitates the ease with which the reinforcing strips  30  can be disposed within slots  25 . Of course, the slots need not extend through the bottom surface  22  and can simply comprise recesses disposed in the front surface or instead proceed through the top surface  23 . As will be apparent to those of ordinary skill in the art in view of the instant disclosure, various slot configurations or combinations of slot configurations are possible within the scope of the present invention. Moreover, the number, spacing and width of slots  25  may vary and will depend upon the desired load rating and intended use environment. As discussed in more detail below, selection of suitable slot dimensions and spacing for any particular application will be within the skill in the are in view of the instant disclosure. However, a potential advantage of the invention is that a given pair of retaining rails  20  can include enough appropriately spaced slots to provide multiple desired load ratings depending on the number and/or gauge of reinforcing strips used. Thus, it is possible with the present invention to be able to provide multiple load ratings using a single rail design, thus obviating the need to manufacture and stock a numerous different reinforcing rail designs. 
   In the preferred embodiment shown, the retaining rails  20  further include apertures  26  disposed in the top surface and extending into the slots  25 . Apertures  26  advantageously enable the provision of enhanced support to the drainage grate surface in the region adjacent the retaining rails  20 . More specifically, apertures  26  are configured to receive an upper edge portion  35 ′ of a reinforcing strip  30  when an end portion of a reinforcing strip  30  is disposed within slot  25 , thereby providing metal-to-metal contact between the upper edge surface  35 ′ of the reinforcing strip and the bottom surface  9  of the drainage grate in the region adjacent the reinforcing rails. 
   The retaining rails  20  are preferably made of plastic. Suitable plastics for use in the invention will be apparent to those of ordinary skill in the art in view of the instant disclosure. Preferably, the plastic is polyvinyl chloride (PVC), high density polyethylene (HDPE) or polypropylene. The retaining rails  20  can be molded or extruded and machined using well known plastic manufacturing techniques within the level of skill in the art in view of the instant disclosure. The retaining rails  20  are preferably injection molded. 
   The metal reinforcing strips can be of any suitable dimension so long as they fit within slots  25  and are capable of spanning the inner diameter of the drainage grate, so that their respective end portions can be retained within the slots  25  of the respective retaining rails  20 . A preferred metal strip according to the invention, shown general at  30  in  FIG. 3A , is configured so as to have shoulder portions  32  which are adapted to fit within slots  25  and, in the preferred embodiments, rest on the inner surfaces of flange portions  7 . As shown, the reinforcing strip  30  includes a thicker body portion  34  for providing additional support to the middle portion of the drainage surface. In each case, the opposed end portions of the reinforcing strips  30  include notches  36  which, as described above, enable upper edge portions  35 ′ to fit within apertures  26 . This preferred configuration provides a secure fit for the reinforcing strips and maximizes the amount of metal-to-metal contact between the upper edge surface  35  and the underside of the drainage surface. 
   As seen in  FIG. 3B , not all reinforcing strips employed in the reinforcing assembly  40  of the invention need be of the same configuration. As seen in  FIG. 1A , if a standard flat reinforcing strip  30  were employed in the last pair of slots at the end of the drainage grate, a significant portion of the surface at the vary end of the grate would go unsupported, as would the corresponding region of the next adjoining grate. This unsupported region is therefore subject to damage and, because this damage could occur at the seem between two adjacent drainage grates, could be quite problematic and potentially dangerous. To remedy this potential problem, the preferred reinforcing assembly  40  includes end reinforcing strips  130 . The particular configuration of the end reinforcing strips can vary and may depend in large measure on the particular nature and configuration of the apertures  11 . The object, of course, is to configure the end reinforcing strip  130  to provide as much support to the very end of the drainage surface as possible, while at the same time maximizing the support to the non-apertured portions of the drainage surface inward thereof. One of ordinary skill in the art will be able to select suitable end reinforcing strip configurations for any particular aperture configuration in view of the instant disclosure. 
   In the preferred embodiment shown in the drawings, end reinforcing strip  130  has a generally sinusoidal configuration adapted to snake around a line of apertures so as to provide support to the drainage surface on both sides thereof. Other than being bent to include aperture accommodating regions  133 , the end reinforcing strip  130  includes an upper edge surface  135  and notches  136  for providing metal-to-metal contact and support to the underside of the drainage surface  3 , shoulder portions  132  for cooperating with the retaining rails, and an enlarged body portion  134  to provide enhanced support to the central region of the drainage grate, all as described above in connection with reinforcing strip  30 . 
   In order to secure the drainage grate assembly to a trench drain, some embodiments will employ a thru-bolt extending through the drainage grate  1  and reinforcing assembly  40 . Although one could simply eliminate reinforcing strips from the region of the reinforcing assembly which must accommodate the thru-bolt, this could undesirably leave portions of the drainage surface unsupported. Accordingly, additional reinforcing strip configurations may be employed to accommodate a thru-bolt or other securing mechanism. Again, the object is to configure the reinforcing strip used for this application to accommodate the thru-bolt or other securing mechanism while at the same time providing as much support to the drainage surface as possible. 
   A preferred reinforcing strip  230  is shown in  FIG. 3C  for use in embodiments of the invention wherein either a thru-bolt or a quick-lock pin, discussed in more detail below, is used to secure the drainage grate assembly. Like reinforcing strips  30  and  130 , the preferred reinforcing strip  230  includes an upper edge surface  235  and notches  236  for providing metal-to-metal contact and support to the underside of the drainage surface  3 , shoulder portions  232  for cooperating with the retaining rails, and an enlarged body portion  234  to provide enhanced support to the central region of the drainage grate, all as described above in connection with reinforcing strip  30  and  130 . As shown, the strip  230  is formed and shaped from sheet metal to include aperture accommodating regions  233  like those of strips  130 , and a pair of opposed end portions  231  on each end to cooperate with a pair of opposed slots in each retaining rail  20 . The upper edges  235  of strip  230  further include a central detent region  239  having a central planar surface  237  which includes a central aperture  238  therein. The central detent region is configured to accommodate an end portion of a quick-lock pin as described in more detail below. However, the central aperture  238  is preferably adapted to accommodate either a quick-lock pin or a thru-bolt. 
   More specifically, reinforcing strip  230  can be disposed in the retaining rails such that the aperture  238  will correspond to and be co-registered with a corresponding thru-bolt aperture  13  ( FIG. 4A ) of the drainage grate  1 . In these embodiments, drainage grate  1  includes one or more apertures  13  for accommodating a thru-bolt or the like for securing the drainage grate to a trench drain or other drainage channel. Typically, the trench drain will include periodic cross members secured therein and spanning the width of the drainage channel. In such arrangements, the cross member includes a threaded aperture for receiving the thru-bolt so that when the bolt is fastened, the drainage grate is secured to the trench drain channel. Other fastening arrangements are also known in the art and suitable for use in accordance with the drainage grate assembly of the invention. As noted, the aforementioned securing strip  230  is adapted to accommodate a thru-bolt through aperture  238 . 
   A preferred means of securing the drainage grate assembly of the invention to the trench drain channel is described in European Patent No. 0605792. Briefly, as seen in connection with  FIGS. 5 and 6 , the drainage grate  1  includes at least one aperture  13  for receiving a thru-pin  41  rather than a thru-bolt. Associated with the thru-pin is a fastening member  42  having an enlarged end  44  for cooperating with a correspondingly shaped clamping spring  46  disposed in a cross bar  48 . When the cross bar member  48  is secured within a trench drain channel so as to span the trench drain channel, the assembled drainage grate  1  can be simply snap-fit into the drainage channel by insertion of the fastening member  42  into the clamping spring  46 . After elastic deformation of clamping spring  46 , the fastening member  42  is secured therein, thereby securing the drainage grate  1  to the trench drain or other drainage channel. 
   A disadvantage of having to employ either a thru-bolt or a thru-pin is the need for the additional thru-bolt or thru-pin aperture  13  and the need to form a recess  15  ( FIG. 4A ) around the aperture to accommodate the head of the bolt or pin so that it sits generally flush with the remaining surface of the grate  1 . In a preferred embodiment of the instant invention the through pin  41  and fastening member  42  are retained in the reinforcing assembly by the design of reinforcing strips  30 ,  130 ,  230 . Accordingly, in the preferred embodiment, the modified strip  230  is employed. As discussed above, the upper edges  235  of strip  230  further include a central detent region  239  having a central planar surface  237  which includes a central aperture  238  therein. The central detent region is configured to accommodate an end portion  43  of a quick-lock pin dispose through aperture  238 , onto which securing member  42  can thereafter be disposed. When opposed ends of strip  230  are disposed within corresponding slots in retaining rails  20 , the end  43  of pin  41  abuts the underside  9  of the drainage surface and is retained there by central planar region  237 . This enables the advantages of the snap-on connection described above in connection with  FIGS. 5 and 6 , without the need for apertures  13  and associated recess  15 , thereby providing a safe and aesthetically desirable drainage surface with substantially continuous support. 
   As will be apparent to one of ordinary skill in the art in view of the instant disclosure, there are numerous configurations which will accomplish this function. For example, the base end of the securing member  42  and/or pin  41  can comprise or be secured to a generally rectangular block or an enlarged flange which is held in place by the upper edges  35  of the substantially flat reinforcing strips  30  being modified to fit around the base end of the member  42  or pin  41 . However, such configurations have the disadvantage of not having any reinforcing strip surfaces in abutment with the underside of the drainage surface on either side of the securing member between the member and the rails. Thus, for example, one could employ two end reinforcing strips  130  adjacent one another and arranged such that aperture accommodating regions  135  accommodate a thru-bolt disposed therebetween. One of ordinary skill in the art will be able to select suitable reinforcing strip configurations for any particular aperture configuration in view of the instant disclosure. 
   In a preferred embodiment, the reinforcing rails  20  and the desired number and gauge of reinforcing strips  30 ,  130 ,  230  are assembled to form reinforcement assembly  40  separately from the drainage grate  1 , which is likewise formed and shaped separately. The reinforcing assembly  40  is thereafter inserted longitudinally into the drainage grate  1  and secured in place. Alternatively, the drainage grate  1  can be formed and then shaped around the assembled reinforcing assembly  40 , whereafter the reinforcing assembly  40  is secured in place within the drainage grate  1 . The reinforcing assembly can be secured within the drainage grate by any means which does not interfere with its ability to properly seat within a drainage channel. Suitable means can include mechanical fasteners or the provision of additional flange portions at opposite ends of the grate  1  which can be bent over, or otherwise cooperate with the opposed end strips  130  of the reinforcing assembly  40  to secure the assembly in place. In the preferred embodiment, the retaining rails  20  includes one or more detents  28 , in their bottom surfaces  22  adjacent the flange portions  7 , whereby the reinforcing member is secured within drainage grate  1  by a simple crimping or stamping action on the portion of the flanges  7  adjacent the detents  28 . 
   As will be apparent to those of ordinary skill in the art, depending upon the number and/or gauge of the metal reinforcing strips present in slots  25 , the reinforcing strength of reinforcing assembly  40 , and hence the load rating of the drainage grate  1  will vary. As a general rule, the thicker the gauge and/or the larger the number of metal strips, the higher the load rating will be. Typical gauges for strips used in accordance with the invention will generally be two millimeters or less. Where it is desired to stock thinner gauge strips, multi-tiered slots may be employed which can securely accommodate a single strip or multiple strips disposed side-by-side within a single slot  25  to achieve the desired effect. In carrying out the invention, one can theoretically obtain load ratings ranging from Class A to Class D or E using the reinforcing assembly  40  of the invention, although other means of reinforcement and or different materials will generally be used to obtain ratings above Class C. However, as load ratings and test methods may vary throughout the world, those of ordinary skill in the art will recognize that the invention does not lie in the ability to achieve any particular standard or specific test specification. Rather, the invention lies in the provision of a reinforcing member which provides a means by which one of ordinary skill in the art can tailor the support provided to any particular drainage grate to any desired load requirements and obtain substantially continuous support. 
   In the preferred embodiments according to the invention, best seen in  FIGS. 1A and 1B , an upper edge of a reinforcing strip is disposed adjacent the underside of the drainage surface between virtually every interval between the rows of apertures, thereby providing substantially continuous support to the drainage grate. Desired load ratings of Class B and Class C can readily be achieved by simply adding metal strips  30  and/or increasing the gauge of the metal strips being employed. In carrying out this aspect of the invention, one can readily approximate the number and/or gauge of metal strips required to obtain the necessary load rating by calculating the I-value for a simply supported beam as is known to those of ordinary skill in the art. However, in practicality, altering the load rating of any particular drainage grate assembly according to the invention is determined empirically by introducing the desired number of metal strips and testing the load rating using a suitable load footprint. This is particularly important because, as noted above, the invention is not limited to the ability to meet any particular rating, test or standard, but can instead be tailored to the needs of any particular situation. In the preferred embodiment, the load rating is empirically tested using a 3 inch by 10 inch load footprint according to DIN 19580 for grates up to 8 inches wide, a 6 inch by 10 inch footprint for grates between 8 and 12 inches wide, and a 10 inch wide footprint for grates in excess of 12 inches, although other suitable methods will be apparent to those of ordinary skill in the art in view of the instant disclosure. 
   Modifications and variations of the invention will be apparent to those skilled in the art in the light of the foregoing detailed disclosure and drawings. Therefore, it is to be understood that, with the scope of the appended claims, the invention can be practiced otherwise than shown and described.