Abstract:
A toilet has a trapway extending between a bowl opening and an outlet opening. The trapway defines a curved, preferably uniform circular cross-section water dam region above the bowl opening, a down leg, and a straight out leg between the down leg and the outlet opening. The down leg has a rearward slope where is located a horizontal baffle. The inclined down leg and horizontal baffle work in concert to prevent the back flow of air to a region above the dam as well as to facilitate rapid entrainment and evacuation of air below the dam.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation-in-part of U.S. application Ser. No. 10/347,740, now U.S. Pat. No. 6,944,891, filed Jan. 20, 2003. 

   STATEMENT OF FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to toilets provided with improved trapways. 
   Conventional toilets have a bowl portion and a storage tank portion, usually formed in one or two main pieces. A serpentine passage is typically positioned behind and below the bowl to transport the contents of the bowl to waste/sewer/septic plumbing lines of the building. This passage is generally referred to as the “siphon” or “trapway”. 
   An up leg portion of such a passage is normally filled with water to “trap” sewer gases downstream thereof, so as to prevent them entering the building interior. Water is maintained in the bowl and the up leg part of the trapway by an arched portion of the trapway. The trapway (sometimes in conjunction with an adjacent jet) generates a siphon to evacuate the bowl contents when a normally air/vapor-filled downstream portion of the trapway is rapidly filled with water during the flush cycle. 
   The trapway thus helps retain water in the bowl prior to flushing, and then assists in the formation of a siphon helpful in removing waste during the flush cycle. Achieving these dual functions can be relatively easy where a large volume of water is used during a single flush cycle. However, for environmental and water conservation reasons many jurisdictions now restrict the sales of toilets which use too much water per flush. For example, some such regulations require no more than 1.6 gallons (6.06 liters) of water to be used per flush cycle. 
   Achieving an effective flush with that little water when the bowl is filled with feces, toilet paper, and other solids can be difficult. Hence, it is common with respect to some such low water usage toilets for consumers to flush the toilet twice or more to clean the bowl to their satisfaction when other than just urine is present. This not only frustrates the regulatory and conservation goals, it is time consuming for consumers. 
   Even where a toilet is reasonably efficient in its cleaning when using low amounts of water, there is also an interest in minimizing the time that the flush cycle takes. A short flush cycle has a number of advantages. For example, the period during which the toilet is generating maximum noise may be reduced if the flush cycle takes less time. This may be of interest if the toilet is being used during the middle of the night and the user wishes to minimize the possibility of others who are sleeping (e.g. a baby) being disturbed. Another advantage of a short flush cycle is that with such a cycle, if a second flush is needed to complete bowl cleaning, it can begin sooner. 
   Various attempts to accomplish a shorter flush cycle have included specially shaping the flow path, controlling the state of flow (turbulent or laminar), and/or reducing or eliminating the occurrence of air pockets at particular locations in the trapway. For example, U.S. Pat. No. 5,918,325 discloses a trapway modified in various ways to attempt to render flushing more optimal. See also U.S. Pat. Nos. 3,484,873, 5,706,529 and 6,292,956. The disclosures of these patents, and of all other patents and publications referred to herein are incorporated by reference as if fully set forth herein. 
   However, attempts to develop quick flush action having efficient cleaning with low volumes of water can be frustrated by “blow back”, which is a tendency of such trapways to develop reverse flow of air from the plumbing lines into a low pressure region of the trapway. Accordingly, there is still a need for low volume flush toilets that have a short flush cycle, yet clean even solid bowl waste effectively and efficiently. 
   SUMMARY OF THE INVENTION 
   The invention provides a toilet having a trapway with improved water and air evacuation characteristics. In one aspect the trapway extends between a bowl opening and an outlet, the trapway having a curved water dam region extending from the bowl opening to above the bowl opening to a down leg. The down leg slopes in a rearward direction from its top to an essentially horizontal baffle extending forward from a rear wall of the down leg adjacent a lower portion of the down leg, the lower portion of the down leg being linked to an out leg communicating with the outlet. 
   Preferably, the dam down leg radius is between about 2.25 and 3.5 inches (, and the down leg slopes less than 15 degrees from vertical, more preferably between about 1 and 8 degrees from vertical. The baffle preferably has a ledge length of between about 0.5 and 2.5 inches measured from the rear wall of the down leg, and even more preferably between about 0.7 and 1.5. The baffle has a ledge height of between about 1.5 and 3.0 inches measured from a bottom of the out leg, and more preferably between about 1.75 and 2.5 inches. 
   In another preferred form, the trapway has a circular cross-section throughout the curved water dam region. The curved water dam region preferably includes a dam down leg radius adjacent the down leg between about 1.5 and 4.0 inches. 
   In other preferred forms at least a portion of the out leg is straight and preferably horizontal, and at least a portion of the down leg is straight. In still other preferred forms the up leg has a circular cross-section, or it has a flat interior wall. In yet another preferred form the out leg has a circular cross-section or a flat interior wall. 
   It is most preferred that the trapway have a minimum ball passage of about 2 inches. 
   In another form the toilet also has a jet providing a capability for a flow rate of between 22 and 28 (preferably about 25) gallons per minute. 
   The present invention thus provides a toilet with a unique trapway design. It is designed so that water from the bowl completely and quickly fills key portions of the trapway during a flush cycle. This leads to rapid evacuation of the bowl contents, minimizing water waste. The trapway design improves the full flush cycle time and significantly improves the rate of the flushing action to nearly half that of common gravity driven toilets with conventional trapway designs. 
   The rearwardly slightly canted down leg reduces the formation of air pockets in the water dam region which would otherwise interfere with the siphoning effect of the trapway. The baffle ledge breaks up the water passing from the down leg to entrain air and particles, and further promote their rapid evacuation through the trapway. The uniform circular cross-section of the curved water dam region helps to lift the surface of the fluid at the water dam during siphon initiation, which further helps to remove air. 
   These and still other advantages of the invention will be apparent from the detailed description and drawings. What follows is merely a description of preferred embodiments of the present invention. To assess the full scope of the invention the claims should be looked to as the preferred embodiments are not intended to be the only embodiments within the scope of the claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a left side elevational view of a toilet trapway according to the present invention, with a typical environment that the trapway can used in being shown in dotted lines; 
       FIG. 2  is a vertical cross-sectional view taken down the front-to-back center line of the rear portion of the toilet of  FIG. 1 ; 
       FIG. 3  is a cross-sectional view taken along line  3 — 3  of  FIG. 2 ; 
       FIG. 4  is a cross-sectional view taken along line  4 — 4  of  FIG. 2 ; 
       FIG. 5  is a reverse side view showing half of the trapway diagrammatically; 
       FIG. 6  is a cross-sectional view taken along line  6 — 6  of  FIG. 5 ; 
       FIG. 7  is a cross-sectional view similar to  FIG. 6 , albeit taken along line  7 — 7  of  FIG. 5 ; 
       FIG. 8  is a cross-sectional view similar to  FIG. 6 , albeit taken along line  8 — 8  of  FIG. 5 ; 
       FIG. 9  is a cross-sectional view similar to  FIG. 6 , albeit taken along line  9 — 9  of  FIG. 5 ; 
       FIG. 10  is a diagrammatic representation of the trapway showing an air pocket (in full cross-hatch) generated by an air dam in an out leg of the trapway and also an air pocket (in phantom) formed by waste line blow back to a low pressure area in a down leg of the trapway not present in the trapway disclosed herein but which did occur in some prior trapway designs; 
       FIG. 11  is a view similar to  FIG. 1 , but of a second embodiment; 
       FIG. 12  is a view similar to  FIG. 2 , but of the second embodiment; 
       FIG. 13  is a cross-sectional view taken along line  13 — 13  of  FIG. 12 ; 
       FIG. 14  is a diagrammatic representation of the trapway of  FIG. 11 , with identification of certain parameters of the trapway: 
       FIGS. 15A and 15B  are cross-sectional views showing alternate versions of an up leg of the trapway taken along line  15 — 15  of  FIG. 12 ; and 
       FIGS. 16A and 16B  are cross-sectional views showing alternate versions of an out leg of the trapway taken along line  16 — 16  of  FIG. 12 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  illustrates a toilet  10  having a siphon passage or trapway  12  design according to the present invention. In particular, other than the trapway  12 , the toilet  10  can be any suitable toilet, preferably of a low volume flush design. 
   For example,  FIG. 1  shows in hidden lines a two-piece type toilet having a separate flush tank  14  mounted to a bowl base  16 . A hole (not shown) in the bottom of the flush tank  14  aligns with a hole (not shown) in the top of the bowl base  16  to allow water to pass from the flush tank and into the a bowl  18 , formed in the bowl base  16 , during a flush cycle. 
   The trapway  12  extends from an opening  20  in the bowl  18  along a serpentine path, having for much of its length an essentially uniform and constant circular cross-section (as shown in  FIG. 3 ). This cross-section is present at least in the second bend  30  at the dam  34 . 
   The trapway has an outlet opening  22  at the bottom of the base of bowl  16 , which mounts over the open end of a waste plumbing line (not shown). The trapway  12  thus creates a path for contents in the bowl  18  to flow to the waste/sewer/septic line during a flush cycle. 
   Referring to  FIG. 2 , an entry  24  of the trapway  12  extends back from the bowl opening  20  to a first bend  26 . An essentially straight backwardly directed up leg  28  extends from the first bend  26  at about a 40–60 degree angle to the second bend  30 . A down leg  32  extends from the second bend  30  declining slightly backwardly from top to bottom away from the opening  20  at, preferably, an angle approximately between 1–10 degrees from vertical, most preferably a 4–6 degree angle. 
   The bend  30  forms about a 40 degree angle between the up leg  28  and the down leg  32  so as to change flow direction about 140 degrees from the direction of flow through the up leg  28 . The surface at the inside diameter of the second bend  30  forms water dam  34  (along the lower inside surface), after which point water can pass through the downstream portion of the trapway  12 . 
   The bottom end of the down leg  32  transitions at another bend  36  which leads to a short, straight forwardly declining leg  38 . Leg  38  terminates at a bend leading to a straight, horizontal out leg  42  ending at a 90 degree bend  44  leading to the outlet opening  22 . 
   The trapway  12  has a generally uniform circular cross-section between the bowl opening and throughout the curved second bend  30  at the water dam  34  and through the down leg  32 . Preferably, the inside cross-section does not vary more than 5 percent in diameter throughout this portion of the trapway  12 .  FIGS. 6–9  illustrate the non-circular cross-sections of the short angled leg  38  and the out leg  42 , which have flat lower surfaces, primarily for casting considerations. 
   Adjacent the bottom end of down leg  32 , the trapway  12  has a short, flat horizontal baffle  46  extending between the rear wall of the down leg  32  and the short angled leg  38 . The baffle  46  preferably extends a length about equal to the radius of the down leg  32 , or in one case about 1 1/16 inches. The baffle  46  works to generate turbulence and change the trajectory of the flow leaving the down leg  32 , which helps move the flow downstream. 
   A recessed cavity or pocket  48 , referred to herein as an air dam  48 , is optionally formed to extend about an upper interior portion of the out leg  42  on a side of a centerline  50  opposite the outlet opening  22 . Preferably, the air dam  48  is adjacent to the intersection of the angled leg  38  and the out leg  42 . The air dam  48  extends upwardly from an upper interior surface of the out leg  42  preferably in a smooth, contoured pyramidal-type configuration such that its base is larger than its tip, as shown in  FIG. 4 . 
   Note, however, that the air dam  48  could be any suitable shape, such as hemi-spherical, as long as a sharp or small radius edge is formed at the leading edge of the air dam  48  sufficient to cause separation of the flow from the trapway  12 . Preferably, the upstream upwardly extending surface  51  of the air dam  48  forms about a 90 degree angle or less to aid in separation of the fluid from the surface of the trapway  12  as described below. 
     FIGS. 7 and 8  show half cross-sections of the through the out leg  42  at the air dam  48 . The air dam  48  can be about ½ to 1 inch (preferably ⅝″) high, about ½ to 3 inches in length (preferably 1½″) and about the diameter of the out leg  42  (preferably 2⅛″). 
   The trapway  12  is designed so that water from the bowl completely and quickly fills key portions of the trapway  12  during a flush cycle. This is achieved because the backwardly canted down leg  32  reduces or eliminates the formation of air pockets at the water dam  34  which interfere with the siphoning effect of the trapway  12 , the uniform circular cross-section of the second bend  30  helps to lift the surface of the fluid at the water dam  34  during siphon initiation. 
   Furthermore, the air dam  48  aids in rapid flushing by separating the fluid from the inside wall of the down leg  32  causing a sheet of fluid within the trapway  12  that tends to block air that may try to pass back through the trapway  12  from the waste line to a low-pressure region in the down leg  42  downstream from the water dam  34 . More specifically, as shown in  FIG. 10 , during flushing fluid passes beyond the water dam  34  into the down leg  32  and the other normally air-filled downstream portions of the trapway. 
   Fluid leaves the lower end of the down leg and into the short angled leg  38 . After leaving the lower end of the short angled leg  38 , fluid at the upper surface (when viewed as shown in  FIG. 2 ) of the trapway passes by a leading edge surface  52  of the air dam  48  (preferably being a small radius convex surface or a short flat sharp angle surface) which leads to the upwardly extending surface  51  of the air dam  48  preferably forming a right or acute angle with the short angled leg  38 . This causes the fluid to separate from the upper surface of the trapway at a relatively high velocity. This in turn causes an air pocket  54  to form generally in the region of the out leg  42  shown by the solid cross-hatching. 
   This effectively reduces the cross-sectional area through the out leg  42 , which increases the pressure and velocity of the fluid through the out leg  42 . This does two things. It increases the rate that the fluid passes through the out leg  42  (despite the smaller cross-sectional area) and causes the fluid to generate a greater down-ward force to counter the force of air in the waste line tending to move to a low pressure region in the down leg  32  and forming an air pocket  56  in the down leg  32  as represented by the hidden line cross-hatching, which is may occur sporadically depending on which pressure prevails. This phenomenon, referred to as “blow back”, is adverse to providing a rapid, powerful flush. Thus, the air dam  48  helps prevent blow back, and thus allows the fluid to pass through the full area of the down leg  32  and short angled leg  38 , and speeds the rate of flow through the out leg  42 . 
     FIGS. 11–14  illustrate another preferred embodiment of the invention, with features analogous to the aforementioned embodiment being referenced using like reference numbers albeit preceded by the numeral “1”. The trapway of this embodiment is of essentially the same construction as the aforementioned embodiment, however, without the air dam feature at the out leg. 
   In particular, like above in this embodiment the toilet  110  has a siphon passage or trapway  112  extending from an opening  120  in the bowl  118  along a serpentine path, having an essentially uniform, cross-section, such as the circular cross-section (as shown in  FIG. 13 ) at the water dam  134 . The outlet opening  122  opening at the bottom of the bowl base  116  mounts over the open end of a waste plumbing line (not shown) so that the trapway  112  creates a path for contents in the bowl  118  to flow to the waste line during a flush cycle. 
   Referring now to  FIG. 12 , a straight entry  124  of the trapway  112  extends back from the bowl opening to a first upward bend  126 . An essentially straight up leg  128 , having an essentially uniform circular (as shown in  FIG. 15A ) or flattened circular (as shown in  FIG. 15B ) cross-section, extends upwardly from the first bend  126  at about a  40 – 60  degree angle to a second bend  130 . A down leg  132  extends from the second bend  130  declining slightly backwardly from top to bottom away from the bowl opening. 
   The second bend  130  forms about a 40 degree angle between the up leg  128  and the down leg  132 . The surface at the inside diameter of the second bend  130  forms the water dam  134  (along the lower inside surface) after which point water can pass from the bowl to the waste line through the downstream portion of the trapway  112 . The bottom end of the down leg  132  transitions at another bend  136  which leads to a short, straight forwardly declining leg  138 . Leg  138  terminates at a bend  140  leading to a straight, horizontal out leg  142  ending at a 90 degree bend  144  leading to the outlet opening  122 . 
   The trapway  112  can have a generally uniform circular cross-sections including between the bowl openings throughout the curved second bend  130  at the water dam  134  and through the down leg  132  (see  FIGS. 13 ,  15 A and  16 A). In this case, preferably, the inside cross-section does not vary more than 5 percent in diameter throughout this portion of the trapway  112 . The up leg  128  and out leg  142  sections of the trapway  112  could, alternatively, have flattened lower surfaces, essentially forming a linear chord surface intersecting the inner diameter of these legs (see  FIGS. 15B and 16B ). This flattened configuration of the up leg  128  and the out leg  142  is similar to the non-circular cross-sections of the short angled leg  38  and the out leg  42  of the aforementioned embodiment shown in  FIGS. 6 and 9 , which have flat lower surfaces primarily for casting considerations. 
   Adjacent the bottom end of down leg  132 , the trapway  112  has a short, flat horizontal baffle  146  extending between the rear wall of the down leg  132  and the short angled leg  138 . The baffle  146  works to generate turbulence and change the trajectory of the flow leaving the down leg  132 , which helps move the flow downstream. 
   The trapway  112  is designed so that water from the bowl completely and quickly fills key portions of the trapway  112  during a flush cycle. This is achieved because the backwardly canted down leg  132  reduces or eliminates the formation of air pockets at the water dam  134  which interfere with the siphoning effect of the trapway  112 , the uniform circular cross-section of the second bend  130  also helps to lift the surface of the fluid at the water dam  134  during siphon initiation. 
   Fluid passes beyond the water dam  134  into the down leg  132  and the other normally air-filled downstream portions of the trapway. Fluid leaves the lower end of the down leg  128  and is interrupted by the baffle  146  before entering the short angled leg  138 . This disruption causes turbulent flow through the out leg  142  which works to entrain air in this region and thereby increase the rate that the fluid passes through the out leg  142  to counter air blow back. 
   With reference to  FIG. 14 , the trapway  112  is configured with several design parameters intended to achieve rapid flushing action. Several of this parameters were discussed above, however, the following table summarizes eleven of the most significant parameters. Where appropriate, a range of preferred values is provided for each parameter. 
   
     
       
             
           
             
             
             
           
         
             
               TABLE 1 
             
           
           
             
                 
             
             
               Trapway design parameters. 
             
           
        
         
             
                 
               Parameter 
               Range 
             
             
                 
                 
             
             
                 
               Trapway up leg radius (r 1 ) 
               2.0–4.0 inches 
             
             
                 
               Trapway up leg angle (θ 2 ) 
                45–60 degrees 
             
             
                 
               Up leg shape 
               Round or flat 
             
             
                 
               Trapway dam up leg radius (r 3 ) 
               1.0–3.0 inches 
             
             
                 
               Trapway dam down leg radius (r 4 ) 
               1.5–4.0 
             
             
                 
               Trapway dam down leg angle (θ 3 ) 
                 0–15 degrees 
             
             
                 
               Trapway corner radius (r 5 ) 
                 1–5 inches 
             
             
                 
               Baffle ledge length (L 1 ) 
               0.5–2.5 inches 
             
             
                 
               Baffle ledge height (h 1 ) 
               1.5–3.0 inches 
             
             
                 
               Out leg shape 
               Round or flat 
             
             
                 
               Outlet diameter (D o ) 
               2.0–3.0 inches 
             
             
                 
                 
             
           
        
       
     
   
   The ranges provided above are selected for a trapway with a ball passage of about 1.8 to 2.1 inches and a toilet with jet way, as understood in the art, providing an initial flow rate of approximately 25 gallons per minute (“gpm”) and a “hold down” flow rate, in which the water level in the bowl is at or below the bowl opening, of approximately 10 gpm. 
   Of the eleven parameters noted above, the inventors of the present invention have determined empirically that the three parameters most critical to rapid flushing are the trapway to dam down leg radius (r 4 ), down leg angle (θ 3 ), and the baffle ledge length (L 1 ). 
   The down leg  132  is designed to extend from the second bend  130  backwardly from top to bottom away from the bowl opening at, preferably, an angle approximately between 1–15 degrees from vertical, more preferably between about 1–8 degrees, and most preferably between about 4–6 degrees from vertical. The down leg trap radius (r 4 ) is preferably 1.5–4.0, and more preferably 2.25–3.5 inches. This radius is selected to help develop the liquid flow profile over the water dam to ensure water flows closely around the inner bend of the water dam and push downstream air in this region toward the outlet. 
   The baffle  146  preferably extends a length of about 0.5–2.5 inches and more preferably about 0.7–1.5 inches for more optimal interruption of the water flow without closing off the passageway excessively. Further, the baffle  146  is preferably disposed at a height of about 1.5–3.0 inches from the lower surface of the out leg, and more preferably at about 1.75–2.5 inches. As mentioned, these valves are selected for a ball passage of about 2 inches. The baffle ledge height and length will vary up or down proportionally to the radius of the down leg. 
   It should be appreciated that preferred embodiments of the invention have been described above. However, many modifications and variations to the preferred embodiments will be apparent to those skilled in the art, which will be within the spirit and scope of the invention. Therefore, the invention should not be limited to the described embodiments. To ascertain the full scope of the invention, the following claims should be referenced. 
   INDUSTRIAL APPLICABILITY 
   The invention provides improved toilets that more efficiently flush waste material by assisting downstream flow of air in the trapway and by resisting upstream air blow back into the trapway.