Patent Publication Number: US-7591111-B2

Title: Inlet flow multiplier and roof drain utilizing same

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This patent application claims the benefit of U.S. Provisional Patent Application No. 60/544,176, filed Feb. 12, 2004, the entire teachings and disclosure of which are hereby incorporated in their entireties by reference thereto. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to water drainage systems, and more particularly to roof water drainage systems and drains used for flat roofs. 
     BACKGROUND OF THE INVENTION 
     Commercial and industrial buildings are typically constructed with flat or near flat roofs. Because these buildings do not have much if any of a pitch to the roof the collection of water on the roof surface resulting from rain and melting snow could present a serious structural load that could result in collapse of the roofs structure. To avoid this possibility most commercial and industrial building standards require that roofs of this type include drains positioned at locations that ensure that at least the majority of water accumulation may be removed from the roof through a drainage plumbing system. 
     Typical roof drains are installed on flat roofs by cutting a hole through the roof deck and installing a drain therethrough. The drain typically connects with drainage plumbing that carries the water away. The drain structure typically includes some form of flashing or collar that, through the application of sealant or other roof material prevents leakage at the site of the drain installation. These typical drain structures also include some form of drain ring and under deck clamping ring or structure that holds the drain in place and prevents its inadvertent removal or dislodgement from its installed position. The opening of the roof drain is typically covered by some form of grating or strainer structure to prevent the ingestion of large objects into the drain plumbing system. In most roof drain structures this strainer or grate takes the form of a hemispherical strainer to prevent or minimize the occurrence of obstruction of the roof drain through the accumulation of leaves and other debris that may accumulate on the roof. 
     Unfortunately, despite the inclusion of a strainer or other grating structure, many roof drains still become plugged or otherwise obstructed to the point that inhibits their ability to remove the accumulated water from the roof of the building. These obstructions can occur as a result of the collection of debris around or over the grate or strainer structure. Additionally, obstructions may also result in the roof drain system during winter months as a result of icing near the roof level of the open areas of the strainer. In addition to the obvious problems resulting from complete obstruction of the roof drains, minor obstructions that merely result in the reduction in the rate of water removal from the roof may also result in undo stress on the roof structure that may endanger its integrity. Additionally, even unobstructed roof drains may not be able to remove water at a rate to prevent its undue accumulation during periods of heavy storms and intense rainfall. 
     In recognition of the limitations of a single roof drain system, many building codes and many more contractors are installing backup roof drains connected to separate drainage system to ensure that the load carrying capacity of a roof structure is not exceeded if the primary roof drain system fails to remove the water accumulation at a sufficient rate. These backup roof drains are typically constructed in the same manner as the primary roof drains, but include a structure that prohibits the drainage of water through the backup drainage system until the level of the water reaches a predetermined depth. That is, the entry ports or slots on the backup roof drains are positioned at a height above the roof surface. This height is preferably chosen based upon the roof construction such that the weight of the water at that given height is well within the load carrying of the roof structure. The separate drainage system ensures that failure of the primary roof drain system due to an obstruction in the drainage system downstream from the roof drains will not affect the ability of the backup roof drain system to remove the water that accumulates above a given depth. 
     While the usage of a primary and backup roof drain system greatly enhances the safety of the roof construction, such also greatly increases the cost of the roof construction. This significant cost increase is a result of the requirement for essential double the number of roof drains that must be installed on the roof. Since typical primary and backup roof drains are of the same construction differing only in the strainer or inlet structure, the cost for such roof drains is essentially double. In addition to the increased cost necessitated by the purchase of twice as many roof drains, each roof drain requires a separate deck penetration or hole to be cut in the roof structure. This essentially doubles the labor cost associated with such a system as twice as many roof penetrations must be cut. Further, depending on the number of primary and backup roof drains that are installed, the overall structural strength of the roof may be weakened due to the large number of deck penetrations that are cut to accommodate both the primary and backup roof drains. 
     While these factors may be considered in the design of a new construction, and therefore compensated, the cost and structural impact to existing buildings that may wish to or are required to install such a backup roof drain system can be prohibitive. That is, on an existing building the roof&#39;s structure and strength are already set, and any impact thereto resulting from the installation of the backup roof drains is not easily compensated. Additionally, the roof surface itself may already be occupied by other equipment that limits the ability to properly position additional backup roof drains to maximize their effectiveness. Further, additional roof penetrations by other system within a building may also limit the ability to install the backup drains at appropriate locations due to clearance requirements dictated by the roof penetrations of the other systems. As a result, the retrofit of an existing building to install the backup roof drain system often is not only expensive but also quite problematic if it can be installed at all. 
     These problems are further exacerbated in areas that receive an abundant amount of precipitation. In such areas, the often rapid deposit of precipitation on the large area of a building&#39;s roof may not be drained away fast enough to keep up with a deluge. This situation often occurs even though the calculated flow from the numerous roof drains should be able to handle the amount of precipitation. The source of this problem relates to the Coriolis forces caused by the Earth&#39;s rotation. These forces result in a swirling vortex being formed around the drains, such as is illustrated in  FIG. 1 . As the flow enters the drain, the vortex is stretched and intensified. As a result, the convergence results in the buildup of a large static head over the drain (see  FIG. 2 ), and ultimately limits the capacity of the drain far below its rated flow capacity. 
     Since many building specifications use the rated flow capacity of the drain pipe to dictate the number and size of the drains needed for a given roof, the existence of these forces and the limiting effect that they have on the water removal capacity of these roof drains can result in a dangerous buildup of water on the roof, especially during periods of heavy precipitation. 
     There exists, therefore, a need in the art for a means to reduce or eliminate the flow reducing effect of the Coriolis forces on drains, and on roof drains in particular. 
     BRIEF SUMMARY OF THE INVENTION 
     In view of the above, it is a general aim of the invention to provide a new and improved roof drain for flat roofs. More particularly, it is a general aim of the present invention to provide a new and improved roof drain that reduces or eliminates the flow reducing effect of the Coriolis forces. Additionally, it is a general aim of the present invention to provide such a roof drain for initial installations on new constructions, and for retrofitting existing structures to include the Coriolis force negative flow effect reducing capability. 
     In one embodiment of the present invention, an inlet flow multiplier (IFM) is included at the inlet of the drain. In this embodiment, this IFM is in the form of a single baffle extending beyond the periphery of the drain inlet, intersecting the opening. Preferably, the IFM dissects the opening of the drain. While the length of the IFM may vary, preferred embodiments of the present invention extend substantially beyond the outer periphery of the drain opening. The length of an exemplary embodiment for use on a 2 inch drain is 10 inches, on a 4 inch drain is 20 inches, and on a 6 inch drain is 30 inches. However, it should be noted that other length IFMs could be used. 
     Other aims, advantages, and features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention, and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a simplified water flow diagram illustrating the swirling effect of water flowing into a drain due to the Coriolis forces; 
         FIG. 2  is a simplified side view of the conical vortex shape and resulting head buildup of the flow of  FIG. 1 ; 
         FIG. 3  is a simplified water flow diagram illustrating the water flow into a drain that includes an embodiment of the IFM of the present invention; 
         FIG. 4  is a simplified side view of the water flow into a drain including an embodiment of the IFM of the present invention; 
         FIG. 5  is a side view illustration of an alternate embodiment of the IFM of the present invention; 
         FIG. 6  is an end view illustration of the IFM of  FIG. 5 ; 
         FIG. 7  is a top view illustration of the IFM of  FIG. 5 ; 
         FIG. 8  is a perspective view illustration of the IFM of  FIG. 5 ; and 
         FIG. 9  is a partial cut-away side view illustration of a bi-functional roof drain incorporating an embodiment of the IFM of the present invention. 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The inlet flow multiplier (IFM)  10  illustrated in  FIG. 3  increases the flow capacity of any arbitrary inlet configuration by perturbing the rotational swirl pattern entering the drain caused by the Coriolis forces discussed above. By perturbing the swirling vortex of a normal drain (see  FIG. 1 ) with the IFM  10  of the present invention, the flow potential of the drain, i.e., the actual flow into a drain in a real world installation, greatly increases. 
     As illustrated in  FIGS. 3 and 4  the IFM  10  is placed over a pipe opening  12  such that it intersects the diameter of the pipe  12 . Preferably, the positioning of the IFM  10  is such that it bisects the drain  12 . As a result of the placement of the IFM  10 , the vortices that would normally form due to the Coriolis forces are obstructed. Instead, the water flow is steered to the drain opening  12 . Standing vortices  13  may be created on the downstream edges of the IFM  10  as the flow impinges on the obstruction. Flow trapped in these small vortices is then directed to the drain opening which is acting as a vortex finder. The remainder of the surface area of the IFM  10  builds a thick boundary layer that, in conjunction with high transverse pressure gradients, steers the remaining flow into the drain. The effect of which is to increase the drains flow efficiency many times over. 
     Indeed, flow test results show that a standard roof drain may only accommodate 100 gallons per minute due to the vortex formed by the Coriolis forces. This 100 gallons per minute flow rate resulted in a seven inch head being established on the roof surface with a given deposition rate of precipitation on the roof. However, when the IFM of the present invention was utilized with the same drain, under the same conditions, the drain accommodated 400 gallons per minute with a four and three-quarter inch head. The flow rate dropped to 300 gallons per minute with a three and one-half inch head, and was measured at 200 gallons per minute with a three inch head. As these dramatic results illustrate, the IFM of the present invention significantly reduces the head and increases the flow rate of the drain by reducing or eliminating the typical vortex formed by the Coriolis forces. Such flow rate increases and reduction in head is significant for building safety, particularly in areas of the world that receive copious amounts of precipitation during a relatively short period of time. 
     In one embodiment of the present invention, the IFM  10  is configured to allow retrofitting of currently installed drain systems via a drain input collar  14  as illustrated in  FIGS. 5-8 . This collar  14  preferably includes clamping flanges  16  to allow a user to securely fasten the IFM to the drain opening. In this embodiment, the clamping of the IFM on the drain opening is accomplished by affixing the collar  14  around the outer periphery of the drain inlet. For installations that do not expose the outer diameter of the drain, other attachment mechanisms may be employed, including a sleeve that is dimensioned to be accommodated within an inner diameter of the drain inlet. 
     As illustrated in  FIG. 9 , a bi-functional roof drain  18  including an IFM  10  is illustrated. The construction and operation of the bi-functional roof drain  18  is as described in U.S. Pat. No. 6,594,966 entitled “Bi-Functional Roof Drain And Method Of Retrofitting A Roof Drainage System Therewith”, the teachings and disclosure of which are hereby incorporated in their entireties herein by reference thereto. As illustrated in this  FIG. 9 , the IFM  10  is positioned to disrupt the vortex formed by the Coriolis forces once the standing water on the roof has reached the backup drain level L. In this way, normal drainage operation occurs through the main drain inlet  20 . However, once the rate of precipitation exceeds the drain capabilities of the standard roof drains and the level of water on the roof rises to the backup drain level, or if the primary drains are plugged resulting in the same condition, the enhanced flow rate through the backup drain system facilitated by the inclusion of the IFM  10  will ensure that a safe condition will be maintained on the roof of the structure. 
     Alternatively, the IFM  10  may be extended downward to the level of the roof line so as to enhance the flow rate of the primary drainage system as well. However, such extension of the IFM  10  is not required with the bi-functional roof drain of the &#39;966 patent based on the construction thereof. 
     All of the references cited herein, including patents, patent applications, and publications, are hereby incorporated in their entireties by reference. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.