Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to the provision of a new form of
cast resiliently-deformable gasket particularly useful for
resiliently supporting a sewer pipe in an openin~ through the
wall of a manhole. It also provides a tight seal, closing the
space between the wall of the openin& and the pipe.
Extruded gaskets are very well adapted for use with sewer
pipe of substantial size. Prior known such gaskets generally had
a hollow nose section integral with a base member, which latter
was embedded in the concrete lining the opening, through which
lo the pipe passes. Such gaskets were generally made by cutting a
length of the lineal extrusion to a size corresponding to the
circumference of the pipe, curving it into the form of a
cylinder, uniting the ends, and then flattening the wall so as to
produce a disk-like washer. That washer had to be held against
considerable internal stress until the concrete had set. In
producing gaskets of relatively small diameter, say 4" or 6", the
strains involved in constraining the cylinder tubular gasket into
a disk-like shape were so great as to limit the use of the small-
diameter sizes.
; 20 It had previously been proposed to use molded gaskets of
elastomeric material, which were shaped like an ordinary washer,
that is, shaped as an apertured disk lying in a single plane.
Such molded washers were embedded in concrete about their outer
margin, and lay normal to the axis of the pipe, They were
subject to the disadvantage that the elastomer used had limited
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stretch in a radially-outward direction. That is, even though it
could be made with an undersized hole, so that the pipe will
stretch the material on being inserted, the amount of stretch was
not sufficient, in the plane of the gasket, to provide enough
freedom for distortion to preserve a tight seal.
The shear stress imposed on sewer pipe passing through a
manhole opening may be very severe indeed, and sometimes, even
though extremely rare, it was sufficient to break the pipe right
off. That eventually was very serious indeed. If the load,
lo including not only the weight of the pipe and its contents, but
also that imposed by fill, traffic stress, and vibration, is
great, the pipe will be driven down into the inner edge of the
rubber in the lower part of the gasket - that is, directly under
the pipe - and the amount of compression may be sufficient to
cause the top of the pipe to pull away from the inner upper edge
of the gasket, thus leaving a small but ruinous lunar opening
between the gasket and pipe. If the elasticity of the
elastomeric material was 6elected to be sufficient to ensure that
its upper rim will follow the pipe even under the stress
conditions stated, it would probably be so "tight" that
insertion of the pipe would be practically impossible. This
factor is important, for the choice of elastomeric material is
limited. The ASTM specifications for rubber gasketed sewer pipe
are quite strict. The elastomer usually conforms to ASTM 443,
SBR 1200, or to ASTM 361, Polystyrene, TS 2400.
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If the embedded por~ions of the gasket are planar and extend
in a normal direction away from the pipe, they may be pulled
ri~ht out of the concrete in which they are embedded, under
stress of axial movement of the pipe.
Among the prior patented gaskets to solve this problem are
the following Canadian Patents:
1. No. 964,043, issued March 11, 1975, APPARATUS FOR
FABRICATING A PIPE JOINT SEALING DEVICE, Granted to
Harry W. Skinner;
2. No. 971,997, issued July 29, 1975, GASKET SEAL BETWEEN
SEWER PIPE AND MANHOLE OPENING, Granted to John
Ditcher;
3. No. 996.150, issued 76/08/31, GASKET SEAL BETWEEN SEWER
PIPE AND MANNOLE OPENING, Granted to John Ditcher;
4. No. 1,018,331, issued 77/10/04, METHOD OF MANUFACTURE
OF MANHOLES WITH RESILIENT SeALS, Granted to Ronald E.
Yoakum;
5. No. 1,077,692, issued 80/05/20, GASKET SEAL BETWEEN
SEWER PIPE AND MANHOLE OPENING, Granted to A-Lok
Products Corporation;
6. No. 1,079,993, issued 80/06/24, MANHOLE SEAL AND METHOD
OF INSTALLATION THEREFOR, Granted to Vibrapipe Concrete
Products Ltd.-Les Produits de Breton Vibrapipe Limitee;
7. No. 1,085,889, issued 80/09/16, GASKET SeAL BETWEeN
SEWER PIPE AND MANHOLE OPENING, Granted to A-Lok
Products Corporation;
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8. No. 1,100,547, issued 81/05/05, MANHOLE SEAL AND METHOD
OF INSTALLATION THEREFOR, Granted to Vibrapipe,
Division of Bestpipe limited;
9. No, 1,112,468, issued 81/11/17, METHOD AND APPARATUS
FOR INSTALLING A GASKET IN THE PERIPHERAL WALL OF AN
OPENING IN A M~SONRY WALL, Gran~ed to Casauton Inc.
10. No. 1,169,837, issued 84/06l26, PIPE SeAL, Granted to
William D. Jones;
In particular, Canadian Patent 1,073,938 issued May 18, 1980
to A-Lok Products Corporation, and its corresponding U.S. Patent
4,103,901 patented August 1, 1978 provided a molded gasket for
resiliently supporting a sewer pipe in a manhole opening, while
sealing the opening against fluid flow. The patented gasket was
a molded annulus of elastomeric material having a peripheral
flange of substantial width and thickness connected by a radially
extending web to an inner concentric rib of greaeer width than
said web, The flange was adapted to be embedded in concrete to
its radially inward face. The rib had an integral circular skirt
extending ir,wardly therefrom in a non-radial direction, and was
united at its rim with a second circular skirt oriented thereto
at a reverse angle. The second skirt merging throughout its
periphery into an O-rin8 of slightly smaller diameter than the
diameter of the sewer pipe it is adapted to surround. Another
embodiment of such molded elastomeric gasket was of circular
shape having an inner toroidal portion adapted closely to embrace
_ 5 _ 1326~50
a pipe, the portion being of substantially smaller inner diameter
than the outer diameter of the pipe, The gasket had an outer
peripheral flange9 T-shaped in section, adapted to be fixedly
anchored in settable ma~erial lining an opening in a manhole
wall, with the base of the T lyin~ radially inward of its head
portion, The toroidal portion merged tangentially with an
integral inner skirt portion, The outer flange merged, a~ the
base of the T, with an outer skirt portion, the inner edge of
the outer skirt being integrally ~oined to the outer edge of the
inner skirt, the whole being characterized in that the combined
width of the skirt portions is greater than the distance between
the toroidal portion and the base of the T-shaped flange.
Other patented gaskets include the following U,S. Patents:
1, 4,084,827 patented April 18, 1978 by Franz-Joseph Wolf,
which taught a ~oint for pipes made of mineral materials
comprising a pipe, a sleeve to receive the pipe, and a gasket
ring carried by the sleeve, The gasket ring comprised a guard
ring and a flange ring, the ~uard ring being mounted in an
annular tee-slot of the sleeve and the flange ring pro~ecting
radially into the sleeve, The sleeve was provided with an
inwardly-pro~ecting inversion ring and with an annular chamber
following the tee-slot, respectively to pivot the guard ring and
then to receive it, when a pipe was inserted.
2, 4,333,662 patented June 8, 1982 by William D. Jones,
which taught a gasket which was particularly suited for sealing
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the annular space between a pipe and a port in an underground
structure is disclosed. The gasket comprised a hollow annular
ring which surrounded the pipe and was connected by a narrow neck
to a base at least partially embedded in the underground
structure. The base had means extending around its outer
periphery to mount the seal securely in the manhole and to
provide a block against water seepage across the periphery of the
gasket.
and 3. 4,387,900 patented June 14, 1983 by A-Lok Products,
Inc., which taught a resilient gasket having an outer annular
flange positioned with a manhole opening and maintained
thereagainst under compression by means of a compression band.
The gasket was provided with a central opening defined by an
; enlarged beaded periphery having an elasticity adapted to tightly
encircle the outer periphery of the pipe. A folded intermediate
section was arranged between and integrally ~oined to the outer
flange and the beaded inner periphery. The intermediate section
was comprised of first and second diagonally-aligned annular
portions integrally ~oined along a fold to define a V-shape,
which imparted a yieldability enabling the gasket to maintain a
watertight seal between the manhole openin~ and the pipe, even in
the presence of a significant misalignment section of the gasket
ad~acent the inner beaded periphery to enhance the watertight
~ seal between the gasket and the pipe. The compression band could
; be provided with pairs of substantially V-shaped slots which
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enabled the band to assume a curvature in a direction transverse
to the curved periphery in order to conform to the curvature of
the manhole opening. The clamping band was formed of a material
which was impervious to the surrounding environment and had a
gap, and a segment hingedly connected to the main body thereof
for placement in the gap and against the interior surface of the
gasket to lock the compression band in position and maintain the
gasket flange under compression,
Many of the above-identified gaskets had certain
disadvantages, among which were the following:
a) they allowed only very limited inclination of the sewer
pipe with respect to its normal axis perpendicular to the plane
of the manhole opening;
b) they did not seal completely round the pipe when the
latter is sub~ected to an abnormally high shearing ~tress;
c) the pipe once inserted into the manhole opening often
could not be withdrawn for inserting it~ outer end into the bell-
shaped spigot connection of the ad~acent sewer pipe wlthout
breakage of the gasket; and
d) a poor seal often effected around the pipe due to
surface irregularities of the pipe surface.
In an attempt to solve those and other problems, Gilbert, in
Canadian Patent 1,207,815 issued July 15, 1986, proposed an
annular elastomeric gasket for resiliently supporting a sewer
pipe in a manhole opening and sealin8 the space between the
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opening surface and the surface of the pipe. The gasket, when in
unstressed state, had an outer cylindrical flange member
extending axially on both sides of a midplane which was normal to
the axis of the pipe. It included a web extending radially-
inwardly from a midsection of the inner surface of the
cylindrical flange member and integral therewith, the web and the
flange being adapted for embedment in settable material lining
the manhole opening. An enlargement extended radially-inwardly
from the web to form a sealing ridge proximate to the web which
lo laterally protruded from one side face of the web, The
enlargement defined a generally-flat lateral surface merging with
the sealing ridge and radially inwardly extending therefrom and
tapering from the ridge towards the midplane, and a sealing lip
depending from the radially inner end portion of the enlargement,
extending at generally right angle to the midplane and laterally
protrudlng from the lateral surface. The lip had a lateral
surface of the enlargement. The lip alco had an inner diameter
substantially less than the outer diameter of the pipe, The
sealing ridge and the sealing lip were adapted to contact the
2~ external surface of the pipe at two axially spaced zones with the
two lateral surfaces defining an annular void therebetween.
That patentee also proposed, as a new article of manufacture
the combination of the gasket with its cylindrical flange member
and web embedded in a channel formed at the opening surface with
the opening surface defining two frusto-conical surface portions
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extending on opposite sides of the channel and web with a first
frusto-conical surface portion disposed on the side of the lip
and sealing ridge and having a minimum diameter which is less
than the minimum diameter of the other frusto-conical surface
portion.
Even the above discussed gaskets did not entirely solve the
above-referred to problems. Consequently, an ob~ect of a broad
aspect of this invention is to provide a molded elastomeric
gasket which would provide a firm support for the pipe, which is
lo sufficiently resilient to compensate for stress in shear,
sufficiently flexible to accommodate extensive misalignment of
the pipe, and yet capable of affording an absolute fluidtight
seal in the rim of the opening, and still further which is easy
to install, comparatively inexpensive to make, and extremely
reliable in use.
It is an obJect of another aspect of the present invention
to provide such a gasket which can effect a seal at two
longitudinally spaced zones around the pipe to effect a double
seal.
An ob~ect of still another aspect of the present invention
is to provide such a gasket which would permit an inclination of
the pipe within the manhole opening without destroying the
sealing effect of the gasket.
An ob~ect of yet another aspect of the present invention
resides in such a gasket which would allow the pipe to be shifted
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in both axial directions with respect to the gasket without
damaging the latter.
An ob~ect of a still further aspect of the invention is to
provide an assembly of a wall having an opening for receiving a
pipe with the surface of the wall opening being non-symmetrical
on each side of the gasket so as to form a step positively to
limit lateral displacement of the pipe under ~bnormally high
shearing force so as to provide a good seal around the pipe even
under such a force.
By one broad aspect of this invention, a cast, resiliently-
deformable gasket is provided for supporting a sewer pipe in a
manhole opening and sealing the space between the walls of the
opening and the surface of the sewer pipe, the gasket comprising:
(a) a generally-pentagonally-shaped, relatively-large mass and
æubstantial thickness main body portion; (b) a cylindrical flange
member in the form of a straight leg portion terminating in an
"L"-shaped foot, the cylindrical flange member being integral
with the main body portion; and (c), a web of substantial
thickness, but which is nevertheless of less thickness than that
of the main body portion, extending radially-inwardly at an acute
angle from the main body portion, the web terminating in a rim
portion of torroidal form, which rim portion is integral with the
web and which has an inner diameter less than the outer diameter
of the pipe; the cylindrical flange and at least half the mass of
the main body portion being adapted to be secured in situ within
the manhole at the manhole opening.
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In such cast gasket, it is preferred that the acute angle at
which the web extends radially-inwardly be 45. The torroidal
rim preferably is of a diameter at least twice the thickness of
such web,
By another aspect of this invention, a new article of
manufacture is provided, by the combination of (I) a manhole
having an opening therein; and (II) a cast, resiliently-
deformable gasket secured _ situ within the manhole opening, the
gasket supporting a sewer pipe in the manhole opening and sealing
lo the space between the walls of the opening and the surface of the
sewer pipe, the gasket comprising: (a), a generally-pentagonally-
shaped, relatively-large mass and substantial thickness main body
portion; (b), a cylindrical flange member which is integral with
the main body portion and which is in the form of a staight leg
portion terminating in an "L"-shaped foot; and (c), a web of
substantial thic~ness but which is nevertheless of less thickness
than that of the main body portion, extending radially-inwardly
at an acute angle from the main body portion, the web terminating
in a rim portion of torroidal form, which is integral with the
web and having an inner diameter less than the outer diameter of
the pipe; the cylindrical flan~e and at least half the mass of
the main body portion being secured _ situ within the manhole at
the manhole opening.
In the accompanying drawings,
Figure 1 is a perspective view of a manhole, with a sewer
' pipe extending thereinto;
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Figure 2 is a section along the line II-II of Figure 1,
showing the cooperation between the gasket of an aspect of this
invention and the sewer pipe;
Figure 3 is a perspective view of a portion of the gasket of
an aspect of this invention; and
Figure 4 i6 an enlarged cross-sectional view of the gasket
of an aspect of this invention.
As seen in Figure 1, the manhole 10 is a precast cylindrical
member 11 with a concrete sewer pipe 12 extending through an
opening 13 therein. The opening 13 is provided with a cast- _-
lo situ, cast gasket 14 to be described in greater detail
hereinafter~
The unique cooperation of the manhole opening 13 and the
gasket 14 in maintaining a seal when sewer pipe 12 i8 inserted
therein is shown in Figure 2. Here is seen that the weight of
the sewer pipe 12 forces the head 15 and the leg 25 of the gasket
14 into its fully compressed position. Nowever, excess
compression is prevented by contact of the sewer pipe 12 at 60
with flattened annulus 61 of the opening 13 where the base of the
sloping face 66 intersects the lower portion of the manhole
opening 13 and by cooperation with components of the gasket 14 to
be described later. It is preferred that face 61 slope at an
angle of 2', that face 66 slope at an angle of 20- and that face
67 slope at an angle of 20-. Sealing contact is maintained
because of the amount of contact between areas 63 of the sewer
pipe 12 and 64 of gasket 14 which includes cooperating components
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of the gasket 14 to be described hereinafter. In addition, the
web and the torroidal rim (to be described hereinafter) provide a
sealing tension where they contact the sewer pipe 12.
This compression does not result in any transfer of forces
to the leg 2~, since (as seen in Figure 4) the forces are
absorbed by the compression of the web 24 into the arcuate
depression provided by arcuate face 19. Moreover, the lower
portion of the body portion 15 as well as the flange 20, i.e. the
leg 21 and the foot 22, are encased by the concrete. Thus, the
lower portion of the body 15 of the gasket 14 and the entire leg
21 and foot 22 are free from forces which might tend to loosen
the gasket 14 from within the concrete of the manhole 11.
Figures 3 and 4 show the cast gasket 14 in greater detail.
The gasket 14 is a cast, elongated, resiliently-deformable, e.g.
elastomeric, for example, rubber, gasket cast as an endless
circular form. It consists of a generally-pentagonally-shaped,
relative large mass and substantial thickness main body portion
15 having a flat rear face 16 and a composite front face composed
of flat face 17 and sloping face 18, sloping at an angle of 45-,
to provide an arcuate face 19, Integral with the main body
portion 15 is a cylindrical flange member 20 in the form of a
straight leg portion 21, coextensive with rear face 16,
terminating in an "L"-shaped foot 22. This provides a large
volume area 23 to be filled with the concrete at the opening 13
of the manhole 11,
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Also integral with the main body portion 15 is a web 24
extending inwardly at an angle of 45~, the web 24 being of
substantial thickness but which is nevertheless of less thickness
than that of the main body portion 15, The web 24 terminates in
a rim portion 25 of torroidal form, which torroidal rim 25 is
integral with the web 24 and which has an inner diameter less
than the outer diameter of the pipe 12.
The cylindrical flange 20 with its leg 21 and foot 22 and at
least half the mass of the main body portion 15 is adapted to be
secured _ situ within the manhole 11 at the manhole opening 13.
Because of this particular structure, the gasket is
sufficiently resilient to compensate for stress in shear, is
sufficiently flexible to accomodate extensive misalignment of the
sewer pipe, and yet is capable of affording an absolute fluid-
tight seal in the rim of the manhole opening. The torroidal rim
provides a sealing tension where it contacts the sewer pipe. The
gasket moreover is easy to install, comparatively inexpensive to
make, and extremely reliable in use.
