Abstract:
The present invention relates to an improved coupling apparatus for tandemly connecting, by hand, separate lengths of a pipe cleaning cable, also referred to as a “snake,” to obtain a cable of extended length suitable for the length of pipe being cleaned.

Description:
BACKGROUND  
         [0001]    The present invention generally relates to apparatus typically used for removing sewer pipe clogs and accumulated debris. More particularly the present invention relates to an improved coupling apparatus for tandemly connecting separate lengths of pipe cleaning cables, also referred to as a “snake,” to obtain a cable of extended length suitable for the length of pipe being cleaned.  
         PRIOR ART  
         [0002]    U.S. Pat. No. 2,880,435 teaches pipe cleaning apparatus, similar to that of the present invention. However, as disclosed and taught in U.S. Pat. No. 2,880,435 an excessive axial force is required to interconnect the cable&#39;s end coupling connectors when assembling tandem lengths of cable. Although prior art U.S. Pat. No. 2,880,435 teaches a sloped entry  2  of female coupling  1 , (see prior art figure) the “435” patent fails to identify the preferred degree or angle of sloped surface  2 . For forty years since the issuance of the “435” patent, industry has chosen a sloped entry surface  2  of forty five degrees. Forty-five degrees is also the apparent slope illustrated in the “435” patent drawings. However, a forty-five degree entry surface  2  has proven to produce a coupling that does not perform in accord with the teaching of the “435” patent. Because of critical structural restraints and requirements placed upon the couplings, the couplings, as taught in the “435” patent, may not be assembled by hand, as represented in the “435” patent, without the use of a hand tool to depress the locking pin of the male coupling during assembly.  
         SUMMARY OF THE INVENTION  
         [0003]    The present invention presents a coupling, suitable for use in a pipe cleaning operation that may be assembled by use of simple hand pressure thereby eliminating the necessity of using a hand tool to depress the locking pin as required in prior art couplings.  
           [0004]    By the present invention the entry chamfered surface of the female coupling is machined at a preferred angle of thirty degrees with the centerline of the coupling whereby simple hand pressure is adequate to connect the couplings without the need for a pin depressing tool as in the prior art. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]    [0005]FIG. 1 presents an elevational view, with parts broken away, of a section of cable including end coupling fittings embodying the present invention.  
         [0006]    [0006]FIG. 2 presents a fragmentary perspective view illustrating two cable coupler sections, embodying the present invention, adapted to interconnect one to the other.  
         [0007]    [0007]FIG. 3 presents a perspective view disclosing two cable coupler sections, embodying the present invention, connected one to the other.  
         [0008]    [0008]FIG. 4 is a crossectional view taken along line  4 - 4  in FIG. 1.  
         [0009]    [0009]FIG. 5 is a crossectional view taken along line  5 - 5  in FIG. 1.  
         [0010]    [0010]FIG. 6 is a crossectional view taken along line  6 - 6  in FIG. 3.  
         [0011]    [0011]FIG. 7 presents a free body diagram illustrating the forces acting upon the male coupling&#39;s locking pin as the couplings are interconnected.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]    Referring to FIGS. 1 through 6, cleaning cable  10  comprises an elongate inner helical cable  12  and an elongate outer helical member  14 . Outer helical cable  14  is rigidly attached at one end thereof to male coupler  18  and at the other end thereof to female coupler  20  by means of threaded engagement with threaded extension  21  provided on coupler  18  and a threaded extension  22  on coupler  20 .  
         [0013]    The convolutions of the outer helical member  14  which engage the threaded extensions  21  and  22  are in juxtaposed relation by action of the helical threads on extensions  21  and  22  as best illustrated in FIG. 1, while the intermediate convolutions thereof are spaced apart.  
         [0014]    The inner helical member  12  is threadedly attached to a threaded finger, connector or stud  24  provided with a lug or lug head  26 . The finger connector  24  is also provided with collar  28  adjacent lug  26 . Each of the threaded extensions  21  and  22  of couplers  18  and  20 , respectively, is provided with diametrically opposed and aligned apertures  32 . Lug  26  is provided with an aperture  34  as shown in FIG. 2. Lug  26  is adapted to be positioned within threaded extension  21  or  22  of cable couplers  18  or  20  such that aperture  34  of lug  26  is in alignment with apertures  32 . A pin  38  is positioned in the apertures  32  and through apertures  34  of lug  26 , retaining the finger connector  24  to coupler  18  or  20 .  
         [0015]    [0015]FIG. 1 illustrates a section of cleaning cable  10  with attached end couplers  18  and  20 . Couplers  18  and  20  may be used to attach a plurality of sections in tandem series relation one to the other to create a total length of cable as may be required during the pipe cleaning process.  
         [0016]    Male coupler  18  is provided with flange  40  separating cylindrical portion  41  from threaded extension  21 . Adjacent the end of cylindrical portion  41  and extending diametrically therethrough and projecting therefrom is fixed pin  42 . The end of the cylindrical portion  41  is provided with tapered portion  43 .  
         [0017]    Intermediate fixed pin  42  and flange  40  is locking pin  44 . Locking pin  44  is disposed in a plane substantially parallel to the plane of pin  42 , however, locking pin  44  is angularly disposed, circumferentially, with respect to pin  42  as illustrated in FIG. 2. Locking pin  44  is recessed in cavity  45  that is closed by cover  46 , see FIG. 4. Cavity  45  contains spring  47  that biases locking pin  44  outwardly. Experience has shown that a preferred force of approximately eight pounds be applied to locking pin  44 , by spring  47 , to prevent locking pin  44  from disengaging from slot  50  during reverse rotation (counter clockwise) of cable  10  during removal from the pipe being cleaned. However, an applied force of between six to ten pounds may suffice depending on the particular end use of the clean-out cable.  
         [0018]    Coupler  20  is provided with socket  48  adapted to receive cylindrical portion  41  of coupler  18  of another section of cleaning cable. Coupler  20  is provided with diametrically disposed L shaped slots  50  which are adapted to receive the protruding ends of fixed pin  42 . The open end of socket  48  includes chamfered portion  52  adapted to engage the spring loaded locking pin  44  and to force locking pin  44  into cavity  45  against the biasing pressure of spring  47  as the cylindrical portion  41  of coupler  18  is fully inserted into socket  48  of coupler  20 . As coupling  18  is advanced, pin  44  is forced radially into cavity  45  by interaction with chamfered surface  52 .  
         [0019]    [0019]FIG. 7 presents a free body diagram of the forces acting upon locking pin  44  and chamfered surface  52  as coupler  18  is inserted into coupling  20  during assembly of two cables. As force F is applied to locking pin  44 , locking pin  44  is opposed by resisting force FR acting normal to chamfered surface  52  and having a horizontal force component FH equal to force F. Force FR further has a vertical component FV which acts to depress pin  44  into cavity  45 . By application of basic rules of trigonometry, the Tangent of angle A1 is the ratio of FH to FV. Therefore, FV is the ratio of FH to the Tangent of angle A1. Thus it is seen that for A1 equaling forty-five degrees FV=FH since the Tan 45=1.00. However, if A1 becomes smaller (less than 45 degrees), the Tangent of A1 becomes progressively smaller thereby affecting a mechanical advantage whereby FV becomes progressively larger as a function of A1 for a given force F. Thus it is possible to increase the effective force FV, acting upon locking pin  44 , by reducing angle A1 from forty-five degrees to a smaller angle such as thirty degrees.  
         [0020]    Therefore by setting angle A1 at thirty degrees the force F necessary to overcome spring  47  and collapse pin  34  into recess  45  may be significantly decreased whereby coupling  18  may be easily interconnected with coupling  18  by hand operation and without the use of a hand tool to depress pin  44  as the couplings are interconnected. Thus for an angle of A1 equal to thirty degrees, a force F of approximately four and a half pounds is required to depress locking pin  44 . Whereas for an angle A1 equal to forty five degrees, as in the prior art, requires a force F of eight pounds to depress locking pin  44 . It has been the field experience that applying a force F of eight pounds is not possible by the average maintenance person, whereas applying a force F of four and a half pounds is within the ability of the average maintenance person.  
         [0021]    Although thirty degrees is considered to be the preferred angle for chamfered surface  52 , it may, depending upon the particular end use of the coupling, possibly range from thirty five to twenty five degrees. However a chamfered surface  52  greater than thirty degrees will obviously result in a greater axial force F being applied to coupling  20  for a given spring  47 .  
         [0022]    Where cable  10  and the attached connectors  18  and  20  typically negotiate a four inch sewer line having “P” traps therein, it is critical that the overall length L1 (see FIG. 3) of the interconnected couplings be no longer than 2.5 inches and the overall outside diameter D must not exceed 1.375 inches. Otherwise the interconnected coupling  15  will not successively negotiate the four-inch “P” trap. Thus with a required length L2=0.625 inches for extensions  21  and  22  to adequately receive thereon convolutions of outer spring  14 , only a length of 1.25 inches remains for the couplings interconnecting and locking elements. Therefore an angle A1 of thirty degrees is considered critical so that sufficient socket wall mass remains, between chamfer  52  and slot wall surface  53 , to bear the load applied by locking pin  44  in operational use particularly during withdrawal of the linked cables when only locking pin  44  applies rotational force upon coupling  20 .  
         [0023]    Because of the torque load applied to the interconnected coupling  15  during pipe clean out it is considered critical that both pins  42  and  44  bare against the complete thickness T of coupling  20 , see FIG. 1 during clockwise rotation  60  of cable  10 . Therefore it is considered critical that pin  44  bare against the radial thickness T associated with surface  51  of coupling  20 , see FIG. 1, and not upon the reduced radial thickness associated with chamfered surface  52 . However, if locking pin  44  is too close to slot wall  53 , sufficient mass of the coupling wall may be insufficient to withstand the circumferential force applied to the coupling wall by locking pin  44  when cable  10  is rotated counterclockwise during removal of cable  10 . Therefore, it is considered critical that locking pin  44  apply its circumferential force, to coupling  20  along line  57  extending radially through the intersection of chamfer  52  and inner wall  51  of coupling  20 . Namely, locking pin  44  is in tangential contact with the wall of slot  50  at line  57 .  
         [0024]    Although the invention has been described in detail with reference to the illustrated embodiment, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.