Patent Publication Number: US-3878569-A

Title: Sewage treatment device

Description:
United States Patent 11 1 Peirish, Jr. et al.  
 1 Apr. 22, 1975 I SEWAGE TREATMENT DEVICE [73] Assignee: International Telephone and Telegraph Corporation, New York. NY.  
  221 Filed: May 2, I974 2| Appl. No.:466,134  
 Prinmry [fawnim-r-Robert l. Smith AIIUI&#39;HC), :lgcnl. or FirmThomas L. Peterson 1571 ABSTRACT A sewage treatment device including a macerator and pumping assembly for use with a toilet of the type utilized in recreational vehicles, such as boats. trailers, or the like. The assembly is mounted near the bottom of a toilet bowl with the macerator adjacent to the outlet of the bowl. The macerator and a pump impeller are mounted on a common shaft rotated by a motor. The impeller is mounted behind the macerator for discharging macerated sewage to waste. The macerator is an auger-like element having a point and a pair of blades formed with spiral-shaped leading edges converging toward the point. The macerator effectivel macerates solid waste and conveys the same axially toward the impeller for rapid evacuation from the toilet bowl with a minimum consumption of water from the bowl.  
 10 Claims, 6 Drawing Figures PMENTEDAPRZZISYS sum 2 0f 5 N QE 0% QV QR fi m 1v? 0% I? 0% w QN. 1 m mm m K V SEWAGE TREATMENT DEVICE BACKGROUND OF THE INVENTION The present invention relates generally to a sewage treatment device and, more particularly, to a macerator and pumping assembly for maccrating solid sewage and evacuating the same from a toilet bowl.  
  Toilet systems for recreational vehicles, such as boats or trailers, utilize pumping assemblies which not only evacuate the waste matter but also supply fresh water to the toilet bowl for the flushing process. The pumping assembly normally employs a chopper or macerator which breaks up the solid waste prior to pumping it through the discharge line of the toilet system. Because of its range of application and type of installation, toilet systems of this type utilize volumes of fresh flushing water and volumes of holding tanks for the wastes which are usually limited.  
  Some prior art macerator and pumping assemblies for such toilet systems have the disadvantage that they require a substantial head of water, or water seal, in the toilet bowl to operate properly. Without a sufficient head of water, cavitation occurs in front of the macerator causing solids to be propelled away from the macer ator rather than toward the impeller behind the macer ator. This may result in the efficiency of the macerator dropping to a level of about percent. As a consequence, there is inadequate evacuation of the waste from the toilet bowl. In addition, on occasions toilet tissue in the bowl tangles on the macerator blades causing the opening between the macerator and the housing wall to become clogged or blocked thus interferring with the evacuation of waste from the toilet bowl.  
  It is, therefore, the object of the present invention to overcome the attendant disadvantages of the aforementioned prior art macerator and pumping unit for toilets by providing an assembly which effectively macerates waste and evacuates the same rapidly with a minimum of water consumption. It is also desirable that the assembly effectively shred toilet tissue so as to prevent any clogging or blocking of the flow passage as occurs occasionally with the prior art macerator and pumping assembly.  
 SUMMARY OF THE INVENTION According to the principal aspects of the present invention, there is provided a macerator and pumping assembly for a toilet in which the macerator comprises a tapered auger-like element having a point and a pair of blades formed with spiral-shaped leading edges converging toward the point. The auger-like element is mounted on a shaft rotatable in a generally cylindrical housing having a tubular elbow section adapted to be connected to the outlet of a toilet bowl. The macerator element is mounted adjacent to such tubular section. The waste pump impeller is mounted behind the macerator. Due to the configuration of the macerator blades, solid waste is effectively macerated and is rapidly conveyed axially toward the impeller so that the waste may be rapidly evacuated from the toilet bowl. This configuration of a macerator has been found not to require a large head of water as in the prior art macerator and pumping assembly discussed above, and does not set up cavitation in front of the macerator which resists the flow of sewage through the assembly, but instead functions in conjunction with the swirling water currents from the toilet bowl to deliver the waste axially toward the impeller for rapid removal. Thus, water consumption by the assembly of the present invention is minimized. Also, it is desirable to provide teeth on the leading edges of the blades of the macerator element which cooperate with longitudinally and inwardly extending teeth formed on the wall of the housing of the assembly to shred toilet tissue and thus minimize if not completely prevent the tangling of tissue on the macerator and, hence. avoid clogging or blocking of the waste flow passage. Other aspects and advantages of the invention will become more apparent from the following description taken in connection with the accompanying drawings.  
 BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a side elevational view ofa toilet employing the improved macerator and pumping assembly of the present invention, with portions of the toilet wall removed to show how the assembly is connected to the toilet components;  
  FIG. 2 is a partial longitudinal sectional view through the macerator and pumping assembly illustrated in FIG. 1;  
  FIG. 3 is a transverse sectional view taken along line 3--3 of FIG. 2 showing the teeth on the macerator element and housing therefor;  
  FIG. 4 is a side elevational view of the macerator element of the present invention, with a portion thereof shown in longitudinal section;  
  FIG. 5 is a front view of the macerator element illustrated in FIG. 4; and  
  FIG. 6 is a front end view of a modified form of the macerator element of the present invention.  
 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. I of the drawings in detail, there is shown a toilet, generally designated 10, including a bowl 12, a seat 14 and a lid 16 disposed over the seat. The macerator and pumping assembly of the invention, generally designated 18, is mounted in the lower portion of the toilet housing 20 below the bowl 12. The assembly 18 comprises a generally cylindrical, horizontally disposed housing 22 having a tubular elbow section 24 which is sealed at its upper end to the outlet 26 of the bowl 12. The right-hand end of housing 22 carries on electric motor (not shown) having a drive shaft 28 which extends axially through the housing toward the elbow section 24, as best seen in FIG. 2. The section of the housing designated 30 contains a fresh water supply pump 32. This pump comprises a rubber impeller fixedly mounted on the shaft 28 and formed with radially outwardly extending vanes 34. The housing section 30 includes an inlet port 36 and an outlet portion on the opposite side of the housing, not visible in the drawings. The inlet port 36 is connected by a line 38 to a fresh water supply, not shown. The outlet port of the pump 32 is connected by a line 40 to an inlet 42 at the rim of the bowl 12. The pump 32 functions to convey water from the fresh water supply to the toilet bowl.  
  The housing 22 also includes an enlarged section 44 in front of pump section 30 in which there is mounted a sewage pump impeller 46 fixed to the shaft 28. The macerator of the present invention, designated 48, is fixedly mounted on the shaft in front of the impeller 46. The enlarged section 44 of the housing is formed with a discharge outlet 50. A waste conduit 52 is connected to the outlet 50. Preferably, a check valve 54 is mounted in the conduit to prevent backflow into the toilet. During a flushing operation, the macerator 48 functions to chop up or finely divide solid waste in the sewage in the toilet 12, while the impeller 46 evacuates the waste sewage from the toilet through the outlet conduit 52 to waste. During the flushing operation, fresh water is supplied to the interior of the bowl 12 by the pump 32 via the lines 38 and 40.  
  Referring now to FIGS. 4 and 5, the macerator 48 comprises a tapered auger-like element comprising a cylindrical shank portion 58 terminating in a point 60 and a pair of integral blades 62 formed with spiral shaped leading edges 64 which converge toward the point 60. The shank 58 is formed with an axially extending bore 66 carrying a metal insert 68. The shank and blades of the macerator are formed of plastic and are molded about the metal insert. The insert has an interfercnce fit with a forwardly extending extension 70 on the shaft 28. Preferably annular ribs 72 are formed on the outer surface of the insert to assure that the plastic macerator is retained on the insert. It is noted that the macerator is mounted on shaft 28 with its point 60 facing forwardly.  
  It is seen that the blades 62 of the macerator element have trailing edges 70 which lie in a common plane which extends generally perpendicular to the axis of the shank 58. The maximum distance between the leading edges 64 ofthe blades (at such plane) is about twice as great as the distance between the plane and the point 60 of the shank.  
  The leading edges 64 of the blades of the auger-like macerator eiement are formed with a plurality of outwardly extending teeth 72. The section 74 of the housing 22 surrounding the macerator is formed with a plurality of longitudinally and inwardly extending teeth 76, as best seen in FIG. 3. Preferably, the teeth 76 are inclined in a direction opposite to the direction of rotation of the macerator 48, indicated by the arrows in FIG. 3. Thus, when the macerator rotates, the teeth 72 on the blades thereof cooperate with the teeth 76 on the housing section 74 to create a shearing action on any toilet tissue which is being evacuated from the bowl 12.  
  Reference is now made to FIG. 6 of the drawings which shows a modified form of the macerator of the present invention, generally designated 48&#39;. This macerator is identical to that described hereinbefore except that the blades 64&#39; are provided with only a single outwardly extending projection or tooth-like element 72&#39; adjacent to the trailing edge 70&#39;. The toothlike ele ments 72&#39; will cooperate with the teeth 76 of the hous ing to shear toilet tissue in a similar manner to the teeth 64 on the macerator 48.  
  The impeller 46 behind the macerator 48 is formed with a plurality of radially and axially extending generally flat blades 78. The impeller may employ for example, four of such blades, only two being visible in FIG. 2. Obviously, a larger or fewer number of blades may be employed if desired. The outlet 50 on the housing is radially aligned with the blades 78. Preferably the blades are formed with cutout sections 80 adjacent to the hub 82 of the impeller which is mounted on the shaft 28. These cutout sections face in the direction of the macerator 48. The cutout sections prevent wads of toilet tissue from becoming entangled upon the impel- [er blades which could jam the impeller and stop the motor in the assembly 18.  
  The macerator 48 of the present invention provides several distinct advantages. It has been found that the auger-like configuration of the macerator sets up a flow pattern that tends to take advantage of cavitation con ditions in front of the macerator and thus actually draws waste from the toilet bowl into the macerator. Also, because of the auger-like configuration of the macerator element, the cross&#39;sectional area of the mac erator is substantially less than that of the housing section 74, thus providing substantial open space therebetween which allows the waste to be pulled rapidly through the macerator. Hence, the auger-like configuration of the macerator conveys the waste axially through the housing rapidly toward the impeller 46 for rapid evacuation by the impeller. Due to the ability of the macerator of the present invention to effectively chop up solid waste and convey it rapidly to the impeller 46, in spite of cavitation conditions in front of the impeller, the macerator does not require a substantial head of water to operate efficiently, thereby resulting in minimum water consumption. In an actual toilet constructed in accordance with the present invention, it has been found that effective flushings may be obtained with the use of only one and a half quarts of water for typical solid waste flushes. Also, as has been previously mentioned, clogging and blocking of the macerator passageway by toilet tissue is minimized, if not avoided, by the provision of the teeth 72 on the macerator and teeth 76 on the housing, as well as the cutout sections on the impeller blades 78.  
  The operation of the macerator element of the pres ent invention has been compared with oth4r types of macerators and found to be far more effective for chopping up solid waste and evacuating the same without high water consumption. Examples of such other maeerators are conventional blendertype chopper blades, circular chopper plates formed with radially and axially extending blades thereon, and circular segmented chopper plates with such blades. [t is seen that none of the other macerator elements which were tested embodied on auger-like configuration, as the macerator of the present invention, with blades having spiraLshaped leading edges converging toward a point, which is believed to be the primary feature of the present invention which facilitates effective maceration of solid waste matter and rapid evacuation thereof with minimum water consumption.  
  While the present invention has been described specifically for use in sewage treatment, it will be appreciated that the macerator may find other useful applica tions where it is necessary to simultaneously comminute and convey solid material in liquid mediums, such as thick pulps, effluents containing fibrous materials, thick slurries, various pastes, etc.  
 What is claimed is:  
  l. A device for treating sewage or the like comprising:  
 a housing including a generally cylindrical section and a forward sewage inlet end;  
 a rotatable shaft coaxially mounted within said cylindrical section;  
 sewage macerating and conveying means mounted on said shaft adjacent to said inlet end of said housing, said means comprising a tapered auger-like element having a forwardly facing point and a pair of blades formed with spiral-shaped leading edges converging toward said point;  
 an impeller mounted on said shaft behind said element;  
 a discharge outlet on said housing in radial alignment with said impeller; and  
 means for rotating said shaft to cause said element to macerate sewage entering through said inlet end and axially convey said sewage rearwardly toward said impeller, and to cause said impeller to discharge said macerated sewage through said discharge outlet of said housing.  
 2. A device as set forth in claim 1 wherein:  
 said forward sewage inlet end comprises a curved, tu-  
 bular elbow section having a circular opening the axis of which extends perpendicular to the longitudinal axis of said cylindrical section.  
 3. A device as set forth in claim 1 wherein:  
 an outwardly extending tooth-like element is formed on the leading edge of each of said blades of said element.  
 4. A device as set forth in claim 3 wherein:  
 the portion of said housing surrounding said element is formed with a plurality of elongated, longitudinally and inwardly extending teeth.  
 5. A device as set forth in claim 4 wherein:  
 said leading edges of said blades are formed with a plurality of said tooth-like elements.  
 6. A device as set forth in claim 4 wherein:  
 said teeth are inclined in a direction opposite to the direction of rotation of said element.  
 7. A device as set forth in claim 1 wherein:  
 said impeller is formed with a plurality of axially and radially outwardly extending blades, said impeller blades having cut-out sections adjacent to said shaft and opening toward said element.  
 8. A device as set forth in claim 1 wherein:  
 said element includes a generally cylindrical shank portion terminating at one end in said point, said blades being integral with said shank and having a trailing edge lying in a common plane generally perpendicular to the axis of said shank, and the maximum distance between the leading edges of said blades is about twice as great as the distance between said plane and said point.  
 9. In a device for treating sewage or the like material a housing having an inlet. a rotatable shaft in said housing, a macerator and an impeller mounted on said shaft with said macerator being disposed between said inlet and said impeller, a discharge outlet on said housing in communication with said impeller, and means for rotating said shaft. the improvement which comprises:  
 said macerator comprising a tapered auger-like element having a point and a pair of blades formed with spiral-shaped leading edges converging toward said point; and  
 rotation of said element by said rotating means causing material entering said housing through said inlet to be macerated and conveyed axially toward said impeller. and pumped by said impeller outwardly through said discharge outlet.  
 10. A device as set forth in claim 9 wherein:  
 said blades are formed with outwardly extending teeth; and  
 the section of said housing surrounding said element is formed with a plurality of longitudinally and inwardly extending teeth.  
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