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The present application claims the benefit of the filing date U.S. Provisional Patent Application No. 60/968,464 filed Aug. 28, 2007 and is a continuation-in-part of U.S. patent application Ser. No. 11/446,026 filed Jun. 2, 2006 now abandoned which claims priority to U.S. Provisional Patent Application Ser. No. 60/714,772 filed Sep. 8, 2005, both applications being incorporated herein by reference. 

   FIELD OF THE INVENTION 
   This invention relates to a sewer hose, particularly adapted for use by removable affixation to a holding tank for drainage, as in connection with the holding tank of a recreational vehicle. 
   BACKGROUND OF THE INVENTION 
   Recreational vehicles, buses, boats and other vehicles with portable living accommodations are commonly equipped with holding tanks for both gray water and sewage. Periodically these tanks must be drained into a sanitary sewage system. The holding tanks are typically discharged into the sewer through a compressible or collapsible hose which can be expanded and fitted both to the holding tank outlet and to an inlet for the sewer. Gravity then induces flow between the holding tank and the sanitary sewage system. In addition to serving in this capacity when the holding tank is to be drained, there are some recreational vehicle facilities with sewer inlets at individual parking locations or campsites so that the sewer hose can connect the recreational vehicle to the sewer for an extended duration. In this arrangement, the waste matter need not be held in the sewage holding tank, but may pass directly to the hose and into the sewer system. The manual connection and disconnection of the sewer hose between vehicle holding tank and sewer inlet can be unsanitary and unpleasant, particularly when there are difficulties with adapters or fittings connecting the sewer hose to inlets and outlets or attendant to cleaning and storage of the sewer hose upon disconnection, as when leaving a campsite. 
   In order to serve its purpose, a sewer hose of this type should satisfy a number of criteria. These criteria include accommodating useful fittings at each end of the hose for fastening to the holding tank outlet, to the sewer inlet, or to another hose when it is necessary to join two sewer hoses for extended length. In addition, the sewer hose should be made of durable material that is chemically resistant so that it will not be damaged by exposure to sewage, and gray water, and sanitizing agents and should be easily cleaned. The sewer hose should also generally be expandable to a significant length when in use yet be collapsible for storage in a relatively compact form as most sewer hoses are stored in either an external cavity on the recreational vehicle or within a sealable plastic container. The sewer hose should be flexible enough to be easily positioned yet sufficiently rigid to maintain the consistent downward pitch from vehicle holding tank to sewer inlet needed for gravity flow. The sewer hose should be resistant to collapse and should resist abrasion and puncture and remain leak free through many cycles of use. 
   Hoses for this purpose have been in use for many years and have almost been uniformly made of strips of flexible vinyl film which are continuously extruded or wound in a helical pattern over a helical steel coil and glued or heat sealed to form a helically corrugated tube. A manufacturing process for hose tubing of this type is described in U.S. Pat. No. 6,024,134 to Akedo, et al. Higher quality sewer hose may utilize polyolefin or polypropylene film. 
   After manufacture of the hose, rigid couplings are threaded into the ends of the hose to facilitate connections to holding tanks and sewers. In some instances the couplings are permanently glued to the ends of the sewer hose, thereby necessitating disposal when the sewer hose is damaged or worn. Other couplings are removable. Since current sewer hoses have either left hand or right hand helixes, the removable couplings are made with corresponding left hand or right hand fittings and the two types are not entirely interchangeable. The structure of these hoses is similar to a plastic or vinyl covered light weight spring, such as the metal spring forming a traditional SLINKY spring toy. When left free, the hose tends to contract and the hose will not generally reach its nominal length unless under tension. The hoses are supple and do not support their own weight or hold a shape or position. Therefore, in order to maintain gravity flow, rigid supports may need to be placed under the hoses. 
   More recently, higher quality sewer hoses have been manufactured where the steel coils are coated with a first color of PVC prior to being wound with polyolefin or polypropylene tape of a second color. In this fashion, should the hose become abraded, as by dragging along the ground, damage penetrating the outer tape layer can be observed by contrast in color. In addition, the steel coil is not immediately exposed to moisture when the outer tape is abraded so that rust does not immediately ensue. This allows the sewer hose to be repaired or replaced in a timely fashion. 
   Furthermore, some of these polyolefin or polypropylene hoses have been made so that the helical corrugations can be expanded and remain open and provide the hose with sufficient rigidity not to require external support. However, these improved hoses are relatively expensive, typically costing between about 2-5 times the price of the ordinary vinyl tape hose. The tapes of all of these hoses are applied in several layers in order to achieve a total wall thickness of between about 15-25 mils. In some instances, the outer layer of tape has been formulated for UV resistance. 
   SUMMARY OF THE INVENTION 
   Therefore, various embodiments of the present invention provide one or more of the following advantages: 
   A sewer hose of the present invention may be open to its rated length and remain in the open state without applied tension, yet be collapsible to only about 20-25% of its rated length and will remain in a collapsed state without external constraints. 
   A sewer hose of the present invention may be formed into complex positions and will maintain these positions in many instances without the need for external supports. For instance, the hose may bridge irregularities in the ground without the need for secondary support. 
   A sewer hose of the present invention maybe formed from a seamless plastic tube so that it is not susceptible to seam related leakage. 
   A sewer hose of the invention may be fabricated without a wire or other hard support necessary to maintain shape and strength of the tubing. 
   A sewer hose of the invention may be manufactured in an extrusion type process and be made from materials from which are not easily adapted to helical seaming. Utilizing an extrusion process allows the co-extrusion in multiple layers of combinations of materials. Through the combination of multiple materials, properties may be selected for manufacture that are not available from a single material, such as chemical resistance and anti-microbial properties for an internal layer, UV resistance for an external layer, and flexibility. 
   By utilizing an inner layer of a first color and an external layer of a second contrasting color, if the crack or abrasion forms on the outer layer, the inner layer will show through indicating the potential failure. 
   A sewer hose of the invention may also be fabricated with ends to incorporate both right hand and left hand helix end sections. For instance, the hose may be made with right hand helix end cuffs immediately external of left hand helix cuff sections. Should it be desired to utilize the hose with right hand helix fittings, it can be used as manufactured. If it is desired to be used with left hand helix fittings, the right hand helix end cuffs are simply cut from the ends thereby exposing the left hand helix cuffs. 
   These and other objections of the invention will become apparent in connection with the following detailed explanation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention may be better understood from the reading of the detailed description in conjunction with a review of the drawings in which: 
       FIG. 1  is a perspective view of a recreational vehicle with a prior art hose connecting the vehicle holding tank to an in-ground sewer inlet. 
       FIG. 2  is a side plan view of an embodiment of a sewer hose having both right hand and left hand helix cuff sections at each end; 
       FIG. 3  is an enlarged side elevation view of the right hand and left hand helix cuff section on one end of the hose. 
       FIG. 4  is an enlarged view of expanded corrugations of the sewer hose of  FIG. 2  in isolation. 
       FIG. 5A  is a sectional end view of sewer hose of  FIG. 2  in a collapsed state. 
       FIG. 5B  is a sectional view of the illustration of  FIG. 5A  taken along line  5 B- 5 B. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1 , there is shown a sewage draining device  2  adapted for use with a recreational vehicle  1  in accordance with one embodiment of the prior art. In conventional systems, a ten or twenty foot length (extended) of flexible drainage hose would often be stored in a special hollow bumper  6  proximal to the holding tank outlet coupling  8 . The entire hose would be removed from bumper  6 , connected at one end to outlet coupling  8  and the opposite end would be inserted into the sewage receptacle  3 . Gray water from sink  7 , or a shower, as well as sewage from toilet  5  is sent to holding tank  4 . When the holding tank valve at the holding tank outlet coupling  8  is opened, gray water and/or sewage flows through the outlet coupling  8  and hose  2  into the sewage receptacle  3 . The prior art hose  2  would also typically be advantageously fitted with a support structure such as disclosed in U.S. Pat. No. 4,228,978; 4,169,571; or 6,619,596 to maintain a consistent downward slope from outlet coupling  8  to sewage receptacle  3 . 
     FIG. 2  depicts an exemplary sewer hose  10  according to the present invention with left hand helix cuffs  20  and right hand helix cuffs  30  integrated into the end sections of the hose and positioned about an intermediate collapsible portion comprised of a plurality of annular corrugations of alternating smaller, minimum or minor diameter rings  16  separated by larger, maximum or major diameter rings  17  being respectively connected by alternating static walls  51  and tuck walls  52  to permit a section of the pipe to be fixed in an extended state  13 ; in a collapsed state  15  or in a curved or directed state  14 . 
   An enlarged view of expanded corrugations is shown in  FIG. 4  and an enlarged view of collapsed corrugations is shown in  FIGS. 5A and 5B . Generally, the sewer hose is in a compressed state when the corrugations are collapsed so that tuck sides  52  are folded inward against static sides  51  as shown in  FIG. 5B . The sewer hose is in an expanded state when tuck sides  52  are folded outward apart from static sides  51  to the extent possible, generally achieving angular orientation between the tuck and static sides of about 90 degrees and possibly even a slightly greater angular orientation. Of particular note in  FIG. 2 , are tooling points, shown as uncollapsable rings  19  with reverse arch shapes. These are desirable for use in manipulating the tubing for packaging. 
   Turning then to  FIG. 3 , an end cuff  11  is shown in isolation with a distal right hand helix cuff  30  separated by trim guide  33  from a proximal helix cuff  20 . If it is desired to utilize a sewer hose  10  with right hand helix fittings, the hose is used in its original configuration. On the other hand, if it is desired to utilize the hose with left hand helix fittings, then the hose is cut along trim line  33  to remove the right hand helix end cuff  30  and the left hand helix end cuff  20  then becomes the distal end of the sewer hose  10 . 
   Some background concerning the measurements applied to corrugated tubing is helpful to their understanding. Corrugated tubing is manufactured in expanded state, typically on a machine called a corrugator. Most corrugated tubing manufactured today is not collapsible. However, when collapsible tubing is manufactured in expanded state, the expanded tubing is collapsed after manufacture, and some permanent deformation occurs. If the collapsed tubing is again expanded, it will not reach its original manufactured length but will typically be about 5%-15% shorter. Subsequent collapsing and expansion does not significantly alter the tubing&#39;s length. Accordingly, all measurements are taken after the tubing has been collapsed and then re-expanded after manufacture. 
     FIG. 4  shows expanded corrugations with tuck wall  52  having a length of 0.278 inches and connected at hinge  53  to static wall  51  having a length of 0.296 inches. Tuck wall  52  is at an angle of 48° with longitudal axis  18  of sewer hose  10  so that tuck angle α (alpha) equals 42° and static wall  51  is at an angle of 45° with longitudal axis  18  so that static angle β (beta) equals 45° thereby resulting in a combined angle of 87° being formed between the tuck wall  52  and static wall  51 . The minor rings  16  have an inner diameter of 2.739 inches  54  and the major rings  17  have an inner diameter of 3.20 inches  55 . The shorter wall lengths and lesser difference between diameters  54 , 55  of minor rings  16  and major rings  17  facilitate the collapsing of the corrugation, as does the preferred wall thickness of only about 0.028 to 0.040 inches that is required due to the simple hinge  53  and shorter distance between smaller and larger rings  16 ,  17 . 
   A relatively uniform wall thickness can be produced on a corrugators. Each corrugation has a width of about 0.50 inches in expanded form. The corrugations of  FIG. 4  are shown in collapsed form in  FIGS. 5A and 5B .  FIG. 5B  is an enlarged view of one end of the section of  FIG. 5A  taken along the line  5 B- 5 B.  FIG. 5B  shows how the tuck wall  52  moves from its original position through the arc  58  by flexing the hinge at  53  so that tuck wall  52  folds against static wall  51 . Thus, the tuck wall  52  proceeds along arc  58  to the position  59 , at which time tuck wall  52  is substantially aligned with the lateral axis or diameter of the major ring  17 , the greatest pressure is exerted to bend tuck wall  52  and compress minor ring  16  so that the tuck wall  52  and smaller ring  16  defined by interior hinge  57  can pass through and be collapsed. In the corrugation design described in  FIGS. 4 and 5 , expansion of corrugations manually can be reasonably achieved as a force of only about 2.5 to 8 pounds is required depending upon the wall thickness and materials. In addition, a bend radius of only about 3.2 inches is achieved. 
   Thus, for this example of sewer hose, the following measures are applicable: 
   Wall thickness=0.35 inches 
   Ratio of static angle β to tuck angle α=1.07:1 
   Sum of α and β=87° 
   Collapse ratio=less than 1:4 
   Bend radius=3.2 inches 
   Ratio of bend radius to maximum diameter=1:1 
   Maximum diameter=3.20 inches 
   Minimum diameter=2.739 inches 
   Ratio of maximum diameter to minimum diameter=1.13:1 
   Length of static wall=0.296 inches 
   Length of tuck wall=0.278 inches 
   Ratio of static wall to tuck wall=1.06:1 
   In particular, a number of desirable characteristics are demonstrated to provide advantages individually and in combination. For a collapsible sewer hose, it is desirable that the wall thickness be between about 0.028 and 0.050 inches, and preferably between 0.030 and 0.040 inches. It is also desirable that the collapse ratio of the corrugated sections be less than about 1:4 and preferably close to about 1:5. Of particular significance for storage in a folded state, it is desirable to achieve a ratio of bend radius to maximum diameter of less than 1.5, and preferably less than 1.4 or 1.35, or even less than 1.1. The illustrated embodiment achieves a ratio of static wall to tuck wall length of less than 1.065 to 1. The ratio of the length of the static wall to the tuck wall is preferably less than 1.35, 1.30, 1.25, or 1.20. The sum of the angles α and β should be more than 80 degrees and less than 110 degrees and preferably less than 100 degrees. The tuck angle α should be at least 2 degrees less than static angle β and the ratio of β to α should be less than 1.25 and preferably less than 1.20, or 1.10. The force required to expand a corrugation should be no more than about eight pounds of force. The ratio to maximum diameter to minimum diameter should be less than 1.15 and the ratio of static wall to tuck wall length can be optimized to be proportionally similar, within about 10% of one another. 
   It will be seen that the corrugated sewer hose of the present invention includes no steel coils or indeed any helical coils of any hard or reinforcing material. In prior art, sewer hoses, it has been deemed necessary to include high tensile spring steel coils to protect the PVC tape hoses from collapsing. However, by extruding a corrugated sewer hose with greater wall thickness, the corrugations are able to withstand abuse and protect against accidental crushing. The variety of materials available for extrusion is broad and may include, for instance, polyurethanes, polyethylene, rubber, nylon, and many plastics. 
   The prior art sewer hoses that maintained their position had wall thicknesses of only about 0.020 inches and when those hoses are extended the tuck and static angles are each greater than 60° for a composite angle of over 130°. The prior static sewer hoses&#39; tuck and static walls were of about equal length. 
   All publications, patents, and patent documents are incorporated by reference herein as though individually incorporated by reference. Although preferred embodiments of the present invention have been disclosed in detail herein, it will be understood that various substitutions and modifications may be made to the disclosed embodiment described herein without departing from the scope and spirit of the present invention as recited in the appended claims.

Summary:
A flexible collapsible corrugated sewer hose has a collapsible and expandable corrugated section providing durability, a tight bend radius and a relatively small collapse ratio. An expansion of the corrugations permits convenient manipulation and installation of the sewer hose having a self supporting structure and crush resistance without helical reinforcement.