Elastic gasket pipe coupling for pressurized plumbing systems

An improved elastic gasket-type pipe coupling device for providing a leak-proof joint between two adjacent pipe segments in a pressurized plumbing system. According to the preferred embodiment of the invention, the pipe coupling includes a cylindrical elastic gasket, a metallic compression band circumferentially disposed about the elastic gasket, and a plurality of tensioning bands attached to and encircling the compression band. The cylindrical elastic gasket includes an inwardly extending, centrally disposed separation ring and at least two integral, inwardly extending sealing rings symmetrically disposed on opposing sides of the separation ring. An enhanced pressure-resistant seal is achieved by locating the tensioning bands at points immediately adjacent to and on both sides of each sealing ring.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to pipe couplings and more particularly 
concerns new and useful improvements in elastic gasket-type pipe couplings 
designed for use in connecting sections of pipe of the type typically 
employed in commercial and domestic sewage, sanitation, and similar 
plumbing systems operating with or without internal pressure. 
2. Description of the Prior Art 
Commercial and domestic plumbing systems, such as those used for sewage, 
sanitation, and the like, generally employ sections of pipe joined 
together in end-to-end relationship with some form of leak-proof coupling. 
Often these pipe sections are made from inexpensive cast iron with wide 
external pipe diameter tolerances and irregular surface features. 
Several different pipe coupling assemblies have been proposed for joining 
pipe segments in end-to-end relationship. One convenient and successful 
coupling assembly is that described in U.S. Pat. No. 3,233,922 wherein a 
cylindrical elastic gasket is positioned around abutting pipe ends with a 
flexible corrugated metallic compression band wrapped around the elastic 
gasket and two or more hose clamps in turn positioned around the outside 
of the metallic compression band to secure the coupling assembly to the 
pipe ends. This elastic gasket-type pipe coupling, however, does not 
provide a leak-proof seal in many pressurized plumbing systems. Sewage 
lines within a high-rise commercial building, for example, will develop 
sufficient pressure over the space of a few stories to induce leakage of 
prior art elastic gasket-type couplings in vertically-oriented pipe 
structures. 
In turn, none of the prior art devices employed in coupling pipe segments 
within a pressurized plumbing system enjoy the ease of installation and 
widespread utility of the elastic gasket-type pipe coupling. Threaded 
joints, the most common type of pressurized pipe coupling, require 
relatively thick pipe walls from which to form pipe threads, and further 
require special sealing compounds to provide a leak-proof seal. Thicker 
walled pipes, however, raise the cost of plumbing systems, and complicate 
the problem of securing the plumbing system within a building structure. 
Welded joints are also commonly employed as pressurized plumbing system 
pipe couplings. Welded joints, however, cannot be dismantled, require 
welding expertise on the part of the plumbing system installer, and create 
a fire hazard during installation and repair. This last consideration is a 
particular disadvantage in plumbing systems intended for use with 
flammable fluids or gases. 
Previous attempts to modify elastic gasket-type pipe couplings for use in 
pressurized plumbing systems have met with limited sucess. One approach, 
illustrated in U.S. Pat. No. 3,359,017, focused on a means of applying 
greater compression forces to the corrugated metallic compression band and 
underlying gasket of an elastic gasket-type pipe coupling. Corrugations on 
a trailing edge of the metallic compression band were tapered off so as to 
terminate in a smooth planar surface. This structure avoided an 
interlocking of corrugations between overlapping portions of the metallic 
compression band which had previously hindered compression of the 
underlying elastic gasket. The greater compression forces more firmly 
sealed the elastic gasket to the outer surfaces of the abutting pipe ends. 
Due to surface irregularities common to the outer surfaces of castiron 
pipes, and the inexact placement of hose clamps compressing the coupling 
assembly, however, this approach provided a leak-proof coupling only in 
lightly pressurized plumbing systems. 
Another approach, disclosed in U.S. Pat. No. 4,101,151, replaced the 
corrugated metallic compression band of the prior art with a slotted 
compression band having a raised central portion and flanged edges. This 
pipe coupling, however, could be used only in conjunction with pipe 
segments having an annular outwardly projecting hub on the outer suface of 
each pipe end, thus precluding the use of this pipe coupling with the more 
commonly available hubless cast iron pipe segments. This hub requirement 
further precluded use of the '151 pipe coupling in conjunction with 
"cut-to-fit" plumbing system assembly techniques. 
Still another effort, disclosed in U.S. Pat. No. 3,581,901, required the 
use of pipe segments having an annular groove cut into the outer surface 
of each pipe end. This annular groove requirement, however, gives rise to 
the same limitations in application as encountered with the '151 pipe 
coupling. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a pipe coupling 
device creating a leak-proof connection between two adjacent pipe segments 
which represents a still further advancement in the state of the art of 
joining pipe segments. The pipe coupling device of the present invention 
provides all the advantages inherent in an elastic gasket-type pipe 
coupling while still forming a leak-proof seal in a pressurized plumbing 
system. Thus a leak-proof pressure-resistant seal may be formed from 
standard, commercially available, cast iron or plastic-type pipe segments, 
which need not be hubbed, grooved, or threaded in any manner. The pipe 
coupling of the present invention will form a pressure-resistant seal 
between two pipe segments of slightly varying outer diameters and 
irregularities in the outer surfaces of pipe segments will not deteriorate 
the quality of the seal. Further, elaborate procedures are not required to 
dismantle the pipe coupling and remove pipe segments from the plumbing 
system as maintenance may require. 
According to the preferred embodiment, the pipe coupling of the present 
invention comprises a cylindrical elastic gasket having a separation ring 
centrally disposed within the gasket and two or more pairs of inwardly 
disposed sealing rings symmetrically arranged about the inner separation 
ring. A metallic compression band having longitudially-oriented 
corrugations is wrapped about the elastic gasket such that the ends of the 
metallic compression band overlap. A purality of tensioning bands encircle 
the metallic compression band to apply compression forces which secure the 
pipe segments and seal the coupling. These tensioning bands are of a 
sufficent number and so arranged about the metallic compression band and 
elastic gasket as to reside on either side of each sealing ring. Direct 
compressional loading of the elastic gasket on either side of each sealing 
ring, rather than by directly compressing each sealing ring, as provided 
in the prior art, creates a leak-proof pipe coupling at pressures 
substantially greater than that achieved by any of the elastic gasket-type 
pipe couplings of the prior art. 
OBJECTS 
It is therefore an object of the present invention to provide an improved 
elastic gasket-type pipe coupling. 
It is a further object of the present invention to provide a pipe coupling 
which will form a fluid-tight joint between two pipe segments in 
end-to-end relationship in a pressurized plumbing system. 
It is a still further object of the present invention to provide a pipe 
coupling between pipe segments having varied outer diameters and irregular 
outer surfaces. 
It is another object of the present invention to provide a pipe coupling 
which is easy to use and does not require any modification of standard, 
commercially available, cast-iron or plastic pipe segments. 
Still other objects, features, and attendant advantages of the present 
invention will become apparent to those skilled in the art from reading 
the following detailed description of the preferred embodiment, taken in 
conjunction with the accompanying drawings wherein like numerals designate 
like parts in the several figures and wherein:

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings and, more particularly, to FIG. 1 thereof, 
there is shown a preferred embodiment of the pipe coupling assembly, 
generally designated 10, of the present invention. The pipe coupling 
assembly 10 is applied to two opposing pipe segment ends 11 and 12, 
arranged in end-to-end relationship. As shown in FIG. 2, a cylindrical 
elastic gasket 13 is situated between the two pipe segment ends 11 and 12 
so as to overlap and surround each pipe segment end. A metallic 
compression band 15 is disposed in overlapping relationship about the 
cylindrical elastic gasket 13. 
The metallic compression band 15 is of substantially the same width as the 
cylindrical elastic gasket 13 and may be made of any ductal 
corrosion-resistant metal. As shown in FIG. 1, the metallic compression 
band 15 is provided with a series of corrugations 17 oriented coaxially 
with the pipe segments. The corrugations 17 permit modest flexibility 
between the adjoining pipe segments while retaining a certain amount of 
rigidity so as to resist transverse forces without buckling. Thus, the 
coupling and resulting plumbing system is capable of flexing through 
modest angles to accommodate some structural flexure as, for example, when 
a building settles. 
The corrugations 17 in the metallic compression band 15 further facilitate 
the leak-proof coupling of two pipe segments of slightly different 
diameters. Due to the relatively inexact casting processes employed in the 
manufacturing of cast-iron pipe, variations in both the outer pipe 
diameter and eccentricity of a pipe segment will occur such that outer 
pipe diameters may vary in excess of one-sixteenth of an inch between pipe 
segments of a particular size. When the pipe coupling assembly 10 of the 
present invention is used to seal pipe segment ends 11 and 12 of slightly 
varying diameter, the corrugations 17 expand or contract as necessary to 
permit the application of roughly equivalent compressional forces to each 
pipe segment end. 
When wrapped about the cylindrical elastic gasket 13, the metallic 
compression band 15 forms an underlying lapped edge and a lapping edge. 
The corrugations 17 of the metallic compression band 15 taper off to form 
a smooth planer surface along that portion of the metallic compression 
band 15 forming the underlying lapped edge. This arrangement of tapering 
corrugations terminating in a smooth planer portion along the lapped edge 
serves to preclude an interlocking of corrugations between the lapped edge 
and lapping edge of the metallic compression band. The obviation of 
interlocking corrugations prevents a build-up of tangential loading forces 
as the metallic compression band is compressed onto the pipe segments 11 
and 12, thereby allowing a greater compression sealing force to be applied 
to tne cylindrical elastic gasket 13 and pipe segment ends 11 and 12. 
Four tensioning bands 21 are affixed to and encircle the metallic 
compression band 15. The tensioning bands serve the dual function of 
securing the opposing pipe ends 11 and 12 within the pipe coupling 10 and 
compress the cylindrical elastic gasket 13 against the pipe ends 11 and 12 
so as to form a pressure resistant seal. 
The tensioning bands 21 of the present invention are of a kind typically 
found in industry and well known in the prior art. These tensioning bands 
21 usually include a band 22 with a screw-type tensioning mechanism 23 
affixed to one end or the band 22 and a plurality of inclined slots 26 
punched through the band 22 along virtually its entire length. The 
screw-type tensioning mechanism 23 may include a screw element 24 designed 
to shear at a specific torque thereby preventing the application of 
excessive compressional forces to the encircled metallic compression band 
15, cylindrical elastic gasket 13 and pipe segment ends 11 and 12. 
Further, where the pipe coupling 10 is installation in an open location, 
the screw element 24 may be provided with a "one-way" slotted head so 
shaped as to permit only tightening of the screw element 24. 
The tensioning bands 21 are attached to the metallic compression band 15 by 
any convenient means, such as rivets 27. Preferrably rivets 27 extend 
above elongated slots 27a formed in each of the bands 21. This 
configuration enables the tension bands 21 to move to a limited extent 
over the compression band 15 as the tension bands 21 are tightened. As a 
result, better sealing can be achieved on maximum and minimum pipe 
connections. As discussed more fully below, the specific placement of the 
tensioning bands 21 along the length of the metallic compression band 15 
is crucial to obtaining a pressure resistant seal. The tensioning bands 21 
should be affixed to the metallic compression band 15 only at points 
approximately one-fourth to one-third of the circumferential distance 
along the band 22 from that end to which the screw-type tensioning 
mechanism 23 is attached. Securing the tensioning bands 21 at points 
further than one-third to one-fourth of this circumferential distance 
gives rise to tangential forces which stretch or flatten the corrugations 
17 in the metallic compression band 15 during compression, thereby 
diminishing the rigidity of the pipe coupling assembly 10. 
It should be understood that a greater number of tensioning bands may be 
used in larger embodiments of the pipe coupling assembly of the present 
invention without departing from the spirit of the invention as set forth 
in the claims below. Six tensioning bands, for example, are recommended to 
provide a leak-proof seal between pipe segments of 5 inches outer diameter 
or greater. 
As shown in FIG. 3, the cylindrical elastic gasket 13 includes as integral 
portions of its inside surface a centrally disposed separation ring 30 and 
two or more circular sealing berms 33. The sealing berms 33 are 
symmetrically disposed on opposing sides of the separation ring 30. 
The cylindrical elastic gasket 13 may be composed of any suitable 
corrosion-resistant synthetic elastameric material. When the pipe coupling 
assembly 10 is placed in sealing relationship between two pipe segment 
ends 11 and 12, only the innermost portion of the separation ring 30 is 
exposed to the inside volume of the pipe segment. Thus, the introduction 
of a fluid or gas into the plumbing system having a corrosive effect on 
the gasket material will not readily contact or deteriorate the sealing 
surfaces within the cylindrical elastic gasket 13. The separation ring 30 
also provides a resilient cushion between the abutting pipe segment ends 
11 and 12 which serves to attenuate the propagation of vibration down the 
length of the plumbing system and accommodates expansion in the pipe 
segments caused, for example, by a rise in temperature of the pipe 
segments. 
As can be seen in FIG. 3 each sealing berm 33 is made up of two annular 
sealing rings 34 and 35 disposed in close proximity to one another and 
formed integrally in and around the inside surface of the cylindrical 
elastic gasket 13. It should be understood that the size and number of 
sealing rings 34 and 35 forming the sealing berms 33 can be varied 
depending upon the surface characteristics of the pipe exterior or the 
internal pressure of the plumbing system. Each sealing berm 33 may, for 
example, be composed of one, two, three, or more sealing rings without 
departing from the spirit of the invention as set forth in the claims 
below. It should be further noted that the number of sealing berms is not 
restricted and may include any number necessary to effectuate an effective 
pressurized seal. On pipe segments having a five inch or larger diameter, 
for example, two sealing berms symmetrically disposed on opposing sides at 
the separation ring 30, making up a total of four sealing berms within a 
single cylindrical elastic gasket 10, would be advisable. 
In operation the pipe segment ends 11 and 12 are inserted into the 
cylindrical elastic gasket 13, and brought into contact with opposing 
sides of the separation ring 30. The tensioning bands 21 are then 
tightened so as to compress the metallic compression band 15, thereby 
forcing the underlying cylindrical elastic gasket 13 against outer surface 
of the pipe segment ends 11 and 12. 
As best seen in FIG. 2, the tensioning bands 21 are affixed to the metallic 
compression band 15 at points along opposing sides of each sealing berm 
33. Each sealing berm 33 is therefore pressed against the outer surface of 
a pipe segment end by compressional forces which are applied directly to 
portions of the inner surface of the cylindrical elastic gasket 13 
immediately adjacent each berm 33. This arrangement avoids a splaying or 
forcing apart of the separation rings 34 and 35 making up each sealing 
berm 33 as the tensioning bands are tightened down. By applying 
compressional loading forces to cylindrical elastic gasket surfaces on 
either side of the sealing berm 33 instead of directly over the sealing 
berm 33, a more effective seal is obtained which is capable of 
withstanding four to five times greater internal pressures than prior art 
elastic gasket-type pipe couplings. The prior art practice of placing 
tensioning bands 21 directly over each sealing berm 33 actually reduces 
the effective seal formed by the cylindrical elastic gasket 13 by forcing 
the sealing rings 34 and 35 apart. 
From the foregoing, it is believed that the invention may be readily 
understood by those skilled in the art without further description. It 
should be duly noted that numerous changes may be made in the details 
disclosed without departing from the spirit of the invention as set forth 
in the claims below. 
A smooth surfaced metallic compression band having logitudinal serrations 
and flanged edges may, for example, be used in place of the corrugated 
metallic compression discused above. Accordingly, it is to be understood 
that the invention is not to be limited by the specific emodiments, but 
only by the scope of the appended claims.