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TECHNICAL FIELD OF THE INVENTION 
       [0001]    The present invention relates generally to drain opening devices, and specifically to the use of compressed air to push obstructions from clogged drains. 
       BACKGROUND OF THE INVENTION 
       [0002]    Water drains typically get clogged due to materials becoming lodged in traps, joints, and other locations. Typically the material causing the blockage or clogging can be freed by applying hydraulic pressure, liquid or gaseous, on the upper region of the drain. Numerous devices available for applying pressure to the blockage, yet they are all deficient in one manner or another. 
         [0003]    Devices commonly referred to as “plungers” comprise a force cup with a handle attached thereto. The force cup is brought into contact with the drain entrance and pushed down by the handle, thereby forcing water to engage the clog with hydraulic pressure and push it down the drain and ultimately out of the way. A force cup device typically does not have sufficient volume to apply sustained and increasing pressure so as to be effective against the blockage material. 
         [0004]    The combination of low and unsustained pressure exerted by force cup devices, and the required reciprocating motion of the plunging action of plungers using force cups, which causes splashing and messy loss of water from the immediate vicinity of a clogged drain, has led to the development of other types of devices. For example, piston devices comprising a piston slidably received within a circular cylinder are an improvement over force cup devices. The piston devices typically comprise a fixed tube with a piston that transits therein to apply pressure at the exit end of the tube. These devices are often adequate for unclogging drains. yet they require many parts and multiple seals thereby increasing the cost of manufacture and the susceptibility of failure during use. Each piston must have a seal between the piston and the cylinder it slides in so as to be effective. The piston must also be sealed to the push rod. Such devices, while functional, have yet to receive widespread acceptance over the simple force cup plunger alone. 
         [0005]    There has been a long felt need in the realm of the plumbing arts for a device suitable for removing blockages from drains in a way that is economical to manufacture, sell, and use, and which is reliable, efficient, and sanitary. 
       SUMMARY OF THE INVENTION 
       [0006]    According to the present invention there is disclosed a drain clearing apparatus comprising a drain engaging element adapted to be mounted to a drain; a hollow shaft, attached at one end to the drain engaging element; an air hose connector attached to the hollow shaft at an opposite end from the drain engaging element; and a flexible air hose having an air hose connector for conveying compressed air from a compressed air source. The drain clearing apparatus also has a drain engaging opening adapted to the drain engaging element so as to make an airtight connection with the opening of the drain. The drain clearing apparatus includes the feature of having the hollow shaft attached to the drain engaging element by a threaded coupling, and it uses a force cup at the drain engaging element. The hollow shaft of the drain clearing apparatus is rigid and is able to transmit axial force and to contain compressed air within itself, and the air hose connector on the hollow shaft couples with an air hose that connected to a compressed air source, the air source being an air compressor, and the air line connector is a quick connect connector. 
         [0007]    According to the present invention there is disclosed a method for clearing blockage from a drain comprising the steps of providing a drain engaging element adapted to be mounted to a drain; attaching a hollow shaft at one end of the drain engaging element; affixing an air hose connector to an end of the hollow shaft at an end opposite from the drain engaging element; attaching a flexible air hose, having an air hose connector, to the air hose connector affixed to the hollow shaft; placing a drain engaging element in airtight contact with a drain; and directing a flow of compressed air through the flexible hose, air hose connector, and hollow shaft to the drain engaging element. The method includes the further step of adapting a drain engaging opening to the drain engaging element, and attaching the drain engaging element to the hollow shaft by a threaded coupling. The method includes the steps of using a force cup as the drain engaging element and making the hollow shaft sufficiently rigid to transmit axially directed force and sufficiently rigid to contain high pressure air within itself. The method including connecting a source of compressed air to the flexible air hose and turning on the source of compressed air, and using a portable air compressor as the source of compressed air. The final steps of the method include using a quick connect connector as the air line connector and sealing the sealing the drain engaging element upon the blocked drain and directing the compressed air to push the blockage from the drain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The structure, operation, and advantages of the present invention will become further apparent upon consideration of the following description taken in conjunction with the accompanying figures (FIGS.). The figures are intended to be illustrative, not limiting. Certain elements in some of the figures may be omitted, or illustrated not-to-scale, for illustrative clarity. The cross-sectional views may be in the form of “slices”, or “near-sighted” cross-sectional views, omitting certain background lines which would otherwise be visible in a “true” cross-sectional view, for illustrative clarity. 
           [0009]      FIG. 1  is an oblique view of the invention showing the main parts. 
           [0010]      FIG. 2  is an orthogonal partial cutaway view of the main part of the invention, showing internal details. 
           [0011]      FIG. 3A  is a cross sectional exemplary view of the invention in use against a drain blockage in a toilet bowl. 
           [0012]      FIG. 3B  is a cross sectional exemplary view of the invention in use against a drain blockage in a water basin. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0013]    In the description that follows, numerous details are set forth in order to provide a thorough understanding of the present invention. It will be appreciated by those skilled in the art that variations of these specific details are possible while still achieving the results of the present invention. Well-known processing steps are generally not described in detail in order to avoid unnecessarily obfuscating the description of the present invention. 
         [0014]    In the description that follows, exemplary dimensions may be presented for an illustrative embodiment of the invention. The dimensions should not be interpreted as limiting. They are included to provide a sense of proportion. Generally speaking, it is the relationship between various elements, where they are located, their contrasting compositions, and sometimes their relative sizes that is of significance. 
         [0015]    In the drawings accompanying the description that follows, often both reference numerals and legends (labels, text descriptions) will be used to identify elements. If legends are provided, they are intended merely as an aid to the reader, and should not in any way be interpreted as limiting. 
         [0016]    Referring now to  FIG. 1 , the main elements of a drain clearing apparatus  10  are shown in oblique view. The drain clearing apparatus  10  includes a force cup  14  made of flexible and pliable material such as natural or synthetic rubber, a rigid handle portion  16  that is hollow, a quick connector  20  consisting of a male portion  20   a  and a female portion  20   b,  another quick connector  30 , and a flexible tube portion  24  that connects to a light weight, portable air compressor  26 . The air compressor  26  is not part of the invention, but the inventor envisions that the invention  10  itself, when purchased, might be supplied with an air compressor ideally matched to the drain clearing apparatus  10  and its operation. 
         [0017]      FIG. 2  shows the drain clearing apparatus  10  of the present invention in partial cutaway, orthogonal view. The force cup portion  14  is made of flexible polymeric material such as rubber. Force cup  14  consists of two main parts, an upper plenum chamber  15  and a lower invertible cup  13  having a circumferential orifice  12 . The function and operation of the invertible cup portion  13  will be described hereinbelow. Also shown in  FIG. 2  is the rigid handle portion  16 , which is connected by a threaded coupling  23  to the force cup  14 , or by any other suitable means. The rigid handle  16  is circularly cylindrical in cross-section and contains therein, an axially centered, inner passageway  17  communicating between the upper plenum portion  15  of the force cup  14  and the rigid handle&#39;s uppermost end  18 , which has attached thereto the male portion  20   a  of a quick connect coupling  20  of the sort commonly used for conveying fluids, both liquid and gaseous, from one conduit to another. In the present case, the male portion  20   a  of a quick connect coupling  20  is connected to the flexible compressed-air conveying hose  24 , by means of the female portion  20   b  of the quick connect coupling, so that the flexible compressed-air conveying hose  24  is connected to the rigid handle  16 . The male portion  20   a  of the quick connect coupling  20  is attached to the rigid handle portion  16  by reliably air-tight means (not shown) such as screw threading, adhesive bonding, polymer welding, or any other of many conceivable techniques, the net result being that the communicating passageway  17  is continuous from the mouth  19  of the male coupling portion  20   a  to the lower end  11  of the rigid handle  16  inside the plenum  15 . The function of the passageway  17  is to communicate pressurized air from the flexible hose  24 , by means of the quick connect coupling  20  when its two components  20   a    20   b  are engaged, to the force cup  14 . While the quick connect coupling  20  has the male portion  20   a  connected to the handle  16  and the female portion  20   b  connected to the hose  24 , it is within the terms of the present invention to mount the male portion  20   a  to the hose  24  and the female portion  20   b  to the handle  16 . 
         [0018]    At distal end  28  of the flexible hose  24 , there is disposed a second quick connect coupling  30  wherein the male portion  30   a  is secured to the flexible hose  24  to engage with a corresponding female quick coupling portion (not shown) that is affixed to an outlet port of the portable air compressor  22 , as shown in  FIG. 1 . Compressed air, denoted by the arrow  34  located at the end  11  of the air-conveying passageway  17  inside the rigid handle  16 , moves from the compressor  26  by way of the flexible tube  24 , and quick connects  20  and  30 , to the plenum chamber  15  of the force cup  14 . 
         [0019]    During use of the drain clearing apparatus  10 , the compressed-air conveying flexible hose  24  is connected at one end by means of the quick connect coupling  30  to an air compressor  26 , and at its other end  21  to the rigid handle  16  by means of the quick connect coupling  20 . As will be shown in detail hereinbelow, the user of the drain clearing apparatus  10  causes the force cup portion  14  of the invention to be brought into air tight contact with the region adjacent the drain of a toilet or water basin wherein the outflow of water is obstructed by a blockage. The user exerts axially directed force upon the rigid handle  16  so as to compress the flexible force cup  14  against a surface that is immediately adjacent to and surrounding the drainage passageway so as to bring about an air tight seal against the loss of fluid or gaseous pressure inside the force cup  14  which is intended to work against the object or material that is obstructive of the flow inside of said drain. The air compressor  26  is then turned on so that air pressure and air volume are brought to bear against the blockage material and against any water that is disposed upstream of said blockage material, thereby pushing said blockage to a wider part of the drain. 
         [0020]    The unique operation of the drain clearing apparatus  10  becomes more specifically evident in the orthogonal cross sectional illustrations of  FIGS. 3A and 3B .  FIG. 3A  shows in cross sectional schematic view a toilet bowl  40  having an outflow drain segment  42 , containing therein water  44  that is blocked from outflow by an obstruction  46 . The invertible flexible cup portion  13  of the force cup  14  is shown engaging the walls  41  of the neck  43  of the toilet drain  42 , thereby creating a seal against the outflow of fluid pressure, water or air, from inside of the force cup. Arrow  47 , shown located within the plenum  15  of the force cup  14 . As compressed air  47  enters the volume defined by the inside of the plenum  15  and the region  48  above the water surface  45 , the pressure of the air is transmitted by those processes that are well-known among those who are skilled in the hydraulic arts such that a net force F is conveyed to the blockage obstruction  46 . The final result is that the force F pushes the blocking obstruction  46  out of contact with the walls  41  of the outflow drain  42 , and thence to a wider part of the drain, thereby affecting the desired result, which is removal of the obstruction from the water drain of the toilet bowl  40 . 
         [0021]      FIG. 3B  shows the operation of the drain clearing apparatus  10  in relation a water basin  50 , shown in schematic cross sectional view. The drain portion  52  of the basin  50  is shown with an obstructing mass  56  disposed within the drain so as to block the passage of trapped water  54 . In the view shown in  FIG. 3B , the invertible flexible cup  13  of the force cup  14  is shown inverted to a position inside of the plenum  15 . In this way, when the user of the invention pushes the force cup  14 , the invertible cup  13  gets creates a seal against the flat surface  51  that surrounds the drain region  52  of the basin  50 . The sealing effect of the invertible cup  13  against basin surface  51  prevents the flow of fluids, liquid or gaseous, from within the volume that is defined by the inside of the plenum  15  and the volume  58  inside the drain and above surface  55  of the trapped water  54 . Thus, as incoming compressed air, which is indicated by arrow  57 , fills the volume  58 , the hydraulic pressure, or pneumatic pressure, of the air is transmitted by those processes that are well-known to those who are skilled in the hydraulic arts such that a net force F′ is conveyed to the blockage obstruction  56 . The final result is that the blocking obstruction  56  is pushed downward along the walls  53  of the outflow drain  52  to a wider portion thereof, thereby ultimately affecting the desired result, which is removal of the blockage  56  from the water drain  52  of the basin  50 . 
         [0022]    Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, certain equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, etc.) the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more features of the other embodiments as may be desired and advantageous for any given or particular application.

Summary:
A drain cleaning device that uses compressed air to clear obstructions in the drain pipes of water basins, toilets and the like. The drain cleaning device consists mainly of a force cup, a handle, flexible pipes for conveying compressed air, and quick connect couplings.