Abstract:
Embodiments include controlled flow rood drains which minimize the size of drainage piping and meet established maximum flow rates by draining built-up water from a flat roof. Embodiments are pre-set by the manufacture in terms of the diameter of the standpipe orifice, which controls maximum flow rate at a predetermined depth of water on the roof, and the height of the standpipe, which determines the depth of water on the roof. Embodiments resist alteration of the flow rate by vandals, tenants, or managers of the building, and are resistant to flow which bypasses the drain control and resistant to plugging by roof debris or snow.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     Embodiments relate to roof installed gated inlet surface drains. 
     BRIEF SUMMARY OF THE INVENTION 
     The efficient drainage of water from flat roofs is an important issue in the construction of commercial buildings. It is important for two reasons to restrict the rate of removal of water from such roofs. Firstly, the capacity of municipal storm sewers often dictate a mandatory limitation on the rate of water which can be removed from a roof and placed in a storm sewer for disposal. Secondly, the cost of drain lines and connector lines which run to the sewer connection constitute a substantial portion of the cost of building manufacture. It is important to minimize the size and thus the cost of these lines. 
     On the other hand, it is important not to exceed the maximum flow rate for the system. If water is removed from the roof at greater than the design maximum flow rate the system will be overwhelmed, with the risk of backflow of water from some drains, as well as the risk of exceeding the mandatory limitation. 
     A common method of minimizing the rate of water removed from a flat roof is to use the roof itself as a reservoir for rain or melted snow water, thereby extending the time available to remove the water from a storm at an optimum controlled rate. The water is allowed to build up to a predetermined height while the excess is drained off at a predetermined maximum rate. 
     In determining the maximum flow rate for a single drain the engineer begins with the 100-year 1-hour rainfall for the location of the installation, the square footage of the roof, and the nature of the roof, i.e. whether it is flat or with a rise or rises, and the structural strength of the roof. Of course, the roof can be used to store rain water only if it is fully waterproof and of sufficient strength to accept the loading of the water. Other engineering considerations, such as the existence and location of parapet walls, wind effects on build-up, and the possibility of roof deflection which could create low spots, must be considered in the drainage design. 
     Alternatively, local codes may dictate the number and location of drains, maximum flow rates for each drain and the maximum allowable build-up. 
     Embodiments include a drain which controls the rate of drainage of water from a flat roof which comprises a cup-shaped body having a connector for connection of the body to a drain pipe. A disk-shaped collar with a hole in the center of the collar is attached to the top of the body and the collar is attached to the roof. A standpipe with a first and a second end, the standpipe having a circular orifice in the side of the standpipe, is connected by the first end coaxially to the hole in the collar with the lowest portion of the orifice on the side of the standpipe approximately at the level of the collar. A grated dome which covers the standpipe is attached to the body. The drain is attached to the roof with the collar level with the surface of the roof, the height of the second end of the standpipe above the collar is the same as the maximum allowed depth of water on the roof, and the diameter of the orifice is adequate to allow the maximum rate of water flow through the orifice at the pressure determined by the maximum allowed depth of water on the roof. 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tool and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following descriptions. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a side view of an embodiment drain. 
         FIG. 2  is a cross-section view of an embodiment drain taken at  2 - 2  of  FIG. 1  and installed on a flat roof. 
         FIG. 3  is an exploded view of an embodiment drain. 
         FIG. 4  is a cross-section diagram showing the relationship between orifice location and head height in an embodiment drain. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In this disclosure the term “flat roof” means a roof which is horizontal throughout; as well as a sloped roof—single rise, a roof with a single rise; a sloped roof—double rise, a roof with a double rise; or a sloped roof—multiple rise, a roof with greater than two rises. The rise is measured vertically from the low point or valley to the high point or ridge and does not exceed 6 inches. The rise is measured vertically from the low point or valley to the high point or ridge of the roof. In this disclosure the term “drain line” means drain pipes, leaders, storm sewers and other pipes which accept water from the roof drains. The term “build-up” means the maximum depth of water on the roof at the drain. In this disclosure the build-up limit is 3 inches for completely level roofs; 4 inches for roofs with a 2 inches rise; 5 inches for roofs with a 4 inch rise; and 6 inches for roofs with a 6 inch rise. 
       FIG. 1  is a side view of an embodiment drain  100 . Visible in  FIG. 1  is the body  10  with sump  14 , outlet  12 , and rim  16 . A collar  20  with a gravel stop  22  with multiple notches  24  also is shown. Visible above the collar is the dome  40  with side grate  42  openings. The location of a standpipe  30  inside the dome is indicated by dashed lines. 
       FIG. 2  is a cross-section view of an embodiment drain taken at  2 - 2  of  FIG. 1  and installed on a flat roof. Visible in  FIG. 2  is the drain body  10  showing the sump  14 , outlet  12 , drain pipe fastener  11 , and rim  16 . Also visible is the collar  20  which rests on the rim  16  with gravel stop  22  which has notches  24  which allow water to pass through the gravel stop  22 . A standpipe hole  25  is in the center of the collar and has a threaded connector  26  which interacts with threaded connector  36  at the second end of standpipe  30  and secures the standpipe in place with the orifice  32  located with the lowest portion of the orifice at the level of the upper surface  27  of the collar  20 . The upper surface  27  of the collar  20  is at the level of the upper surface  53  of the roof which is the top of the membrane  52  in the embodiment of  FIG. 2 . Standpipe  30  also has a cap or closure  38  at the first end  33  of the standpipe in this embodiment. The roof body  50  is shown as a concrete structure in this embodiment. 
     Also visible in  FIG. 2  is the dome  40  showing the side  41  with grated openings  42  and the top 43 of the dome with top grate  44  openings. A rim  46  is at the bottom of the dome and has a vandal-resistant latch which interacts with a latch on the collar (not shown in  FIG. 2 ). 
     The embodiment in  FIG. 2  has a body with a straight-sided outlet  12  which uses a rubber drain pipe fastener  11  to connect with the drain pipe  54 . A suitable body is the no-hub body obtainable from J.R. Smith Mfg. Co., Montgomery, Ala. A suitable drain pipe connector is the SPEEDI-SET gasket obtainable from J.R. Smith Mfg. Co. SPEEDI-SET is a trademark for gaskets belonging to the J.R. Smith Mfg. Co. 
     Other connector types for connecting the drain pipe and drain body are specifically contemplated. In particular, a connection which comprises oakum and lead is specifically contemplated. The connection of a no-hub body to a drain pipe using a no-hub clamp is specifically contemplated. 
     While not depicted in  FIG. 2 , a variety of means may be used to securely connect the drain with the roof, for example, an under deck clamp. Such a clamp is a halo-shaped flange through which the drain body extends, which bears against the bottom side of the roof, and which is secured to the drain body by bolts. 
       FIG. 3  is an exploded view of an embodiment drain  100 . Visible in  FIG. 3  is the body  10  with drain pipe connector  10 , sump  14 , fastener receivers  13 , and rim  16 . Also visible in  FIG. 3  is the collar  20  with gravel stop  22 , notches  24 , and fastener holes  23 . Also visible is a standpipe hole  25  located in the center of the collar. The circumference of the hole is threaded  26  for interaction with the threads  36  at the first  35  end of the standpipe  30 . A vandal-resistant latch  28  for securing the dome to the collar is shown in  FIG. 3 . Threaded bolt fasteners  21  extend through the holes  23  and interact with threaded fastener receivers  13  to secure the collar  20  to the body  10 . A standpipe  30  is shown with a second end  33  with an opening  34  in this embodiment standpipe. An orifice  32  is shown on the side of the standpipe. The first end  35  of the standpipe is threaded  36  and interacts with the threads  26  on the collar hole  25  to secure the standpipe in the collar. Also visible is a truncated cone-shaped dome  40  with sides  41  with grated  42  openings. The top 43 of the dome has grated  44  openings. A vandal-resistant dome latch  48  interacts with the collar latch  28  to secure the dome in position on top of the collar. 
     In embodiments, the fasteners which attach the collar to the body are bolts. Other suitable fasteners include screws, pegs, pins, and grommets. 
     In embodiments, the standpipe is attached to the collar through a joint with threads on the outer circumference of the standpipe which interact with corresponding threads on the circumference of the hole in the center of the collar. Other types of joints between the standpipe and collar are specifically contemplated, such as a bayonet mount, friction joint, permanent or semi-permanent joints such as by welding, soldering, or adhesive joints. 
     In embodiments, the dome is attached to the collar by a vandal-resistant latch. Other suitable attachment mechanisms, including lugs and a bayonet locking device are specifically contemplated. 
       FIG. 4  is a cross-section diagram showing the relationship between orifice location and head height in an embodiment drain. Visible in  FIG. 4  is the roof body  50  with membrane  52  and upper surface  53  of roof, here the upper surface of the membrane  52 . The body rim  16  is shown as well as the collar  20  with gravel stop  22 , upper surface  27  of collar, standpipe hole  25  and threaded  26  standpipe connector on the collar. The standpipe  30  is shown with orifice  32  and threaded  36  first end  35  of the standpipe. In this embodiment standpipe a cover  38  is located at the first end  35  of the standpipe. The height of the head  58  is the maximum allowable height of water  56  allowed to accumulate at the drain. Note the lowest portion  31  of the orifice  32  is at the level of the upper surface  53  of the roof. 
     Embodiment drains are manufactured of any strong, durable, impermeable materials. Embodiment domes, standpipes, collars and bodies are manufactured of polyethylene, other plastics, aluminum, bronze, steel, stainless steel, galvanized cast iron and cast iron. 
     Embodiment roof drains serve to drain water from flat roofs at a predetermined maximum rate. 
     In embodiments, the maximum drain rate through the orifice, which determines the maximum drain rate through the drain, is set by the manufacturer and cannot be altered. Similarly, the maximum build-up of water, which is determined by the height of the standpipe above the collar, or by overflow drains, is set by the manufacturer and cannot be altered by the user. These provisions insure durability, reduce the cost of manufacture, eliminate the possibility of inadvertent alteration of settings controlling flow rate and build-up, and prevent deliberate or inadvertent alteration of the flow rate and build-up by builders, tenants, or vandals. 
     In embodiments, the drain is permanently mounted on the roof. This insures that water cannot infiltrate under the collar and by-pass the build-up control of the standpipe, despite the existence of irregularities in the surface of the roof. Furthermore, excessive winds cannot shift, tip-over, or remove embodiment drains. 
     In embodiments, the second end of the standpipe is closed. In these embodiments the drain acts solely as a means for providing controlled drainage from a flat roof. 
     In embodiments, the second end of the standpipe is open. In these embodiments the length of the standpipe is set so that the top of the standpipe is the same height above the roof as the allowed depth of build-up. Here the drain has two functions, that of providing controlled drainage from a flat roof, and that of acting as an emergency drain under the unusual conditions of orifice plugging. An orifice might be plugged by icing conditions or be an unusual accumulation of mud or debris on the roof. 
     In embodiments, the orifice is sized as follows: 
     Step 1. Determine the allowable drainage rate for the roof from the municipality officials. 
     Step 2. Determine the roof area for an individual drain. 
     Step 3. Calculate the maximum controlled flow gallons per minute (GPM) for each roof drain based on rainfall intensity and square footage of the roof and the allowable drainage rate for the roof. 
     Step 4. Set the maximum build-up by the height of the overflow drains. 
     Step 5. Calculate the orifice size based on the required controlled flow GPM per drain Using McNally Institute “Approximate flow through an orifice” as in Formula 1.
 
 Q= 448.8× K×A×√ 2 gh  when  Formula 1
 
Q=controlled flow GPM per drain
 
448.8=conversion factor from cubic foot per second to GPM.
 
K=orifice constant=0.512.
 
A=orifice area in square feet.
 
g=specific gravity of 32.2 ft/sec 2 .
 
h=head at orifice in feet.
 
     Example 1 
     The orifice size for embodiment example “A” is calculated using Formula 1 as follows: Q for embodiment A=12 GPM at 0.25 ft head.
 
12=448.8× K×A×√ 2 gh  
 
12=448.8×0.512× A× 4.012
 
12=922× A  
 
A=0.013 square feet. This indicates an orifice diameter of 1.54 inches.
 
     While a number of exemplary aspects and embodiments have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope. The applicant or applicants have attempted to disclose all the embodiments of the invention that could be reasonably foreseen. There may be unforeseeable insubstantial modifications that remain as equivalents.