Note: Descriptions are shown in the official language in which they were submitted.
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LARGE DIAMETER DO~B~E-WALLED
PLASTIC PIPE
.
I. DESCRIPTION
......... _
Background of Prior Art
The coupling of in~ividual plastic pipe sections,
has been troublesome for many years because of the amount
of time consumed in making the connection and the atten-
dant excessive expense and labor, as well as the diffi-
culties experienced with some type of couplings because of
inaccessibility of the connector ele~ents once the connec-
tion had been accomplished, as well as the aifficulties
experienced with some type of couplings because of their
inherent inability to prevent uncoupling as a result of
retractive forces exerted upon one or 20th of ,he con-
lS nected pipe sections. Addi.ionally, the i~tr~duction in
recent years of corrugated pipe in ircreasingly lGrger
sizes of 8 inches and larger, havir,g ciLferent coupling
characteristics because of correspondinsly gre~ter corru
gation pitches, deeper valleys, thicker walls, and greater
rigidity and inflexibility required to meet industry stan-
dards and performance specifications, has created 2 need
for previously unnecessary and consequently unanticipated
types of coupling systems, which are not taught by the
prior art. Additionally, the increasing recognition and
popularization of the userulness of this pipe in more
demanding and more stringent end use applications such as
culverts and storm sewers, in addition to the traditional
land drainage applications, has created a need for
improved coupling systems of types previously unnecessary
~o and consequently unanticipated and unknown. Outlined
hereinbelow are some of the known and currently utilized
types of coupling systems which are inherently unsatisfac-
tory for use with such pipe over the current and projected
future range of end use applications.
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Pipe constructed as in the Maroschak Patent No.
3,899,198 is not connectable in the larger sizes because
the ma~erial will not stretch or deflect sufficiently so
that the connection can be accomplished by manually forcing
one end of the pipe into the connector. In other words,
the labourer laying the pipe cannot exert sufficient axial
pressure to effect the connection. Additionally, the
Maroschak patent describes a design to perform the express
function of providing for a releasable connection. This
function is totally inappropriate in a coupling system
intended for use over a range o~ end use applications
including those in which non-releasable connections are
highly desirable and releasable connections are
unsatisfactory.
As shown below and in the Maroschak patent above,
efforts have been made to design and produce separate
plastic couplings in the form of separate sleeves, but
these designs have proven unduly cu~bersome, expensive,
. time-consuming and generally inadequate with the smaller
pipe sizes and inappropriately designed to function
properly with the larger pipe sizes and in the more
demanding and more stringent end use applications, such as
culverts and storm sewers. Additionally, none of such
patents address the problems involved with double-walled
pipe. One coupling has previously been designed as an
integral part of the plastic pipe, as shown in U.S. Patent
4,247,136, Fouss et al, issued on January 27, 1981, but it
has several disadvantages, one of whicA is its
inaccessibility once the two ends of pipe have been secured
thereby.
Another disadvantage is that the reduced diameter o~
this co~pling constricts the inner diameter of the piping
system at all coupled connections. This reduces the system
flow capacity accordingly. This also introduces multiple
points at which any carried solids can catch and build up
and at which iron ochre deposits can grow and build up
und~r certain conditions. Both of these conditions can
restrict flow and, in extreme cases, create blockages
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causing the sy~tem failure. Also, since the latching
elements are formed in the interior or male segments of the
coupling, the fluid being conv~yed in the pipe will be
contaminated by fluid on the outside walls of the pipe
which is retained within and around the latching elements.
Brief summary of the Invention
Our invention includes the method of continuously
manufacturing double-walled plastic pipe, the outer wall of
which is corrugated and the inner wall of which is smooth
and continuous, the two walls being integrally molded of
high density polyethylene, PVC, or polypropylene. The pipe
is cut into sections so that relatively short and enlarged
connector portions thereof are carried at one end of each
section. The cuts are made as defined in the claims to
provide a smooth continuous inner wall when the sections
are connected. The molding apparatus which we utilize is
conventional, similar to that shown in U.S. Patent
4,439,130, Dickhut et al, issued on March 27, 1984.
Our invention also includes the pipe itself,
particularly the female conn~ctor portion at one end of
each section which is constructed and arranged so that
despite the necessary inflexibility of the wall structure,
the opposite end portion of a similarly constructed section
may be quickly, easily and efficiently manually inserted
thereinto and automatically connected thereto in non-
~ releasable positive interlocked relation~ This is made
; possible through the use of an integrally molded enlarged
sleeve having hinged latching members extending inwardly
from the wall of the sleeve and construc~ed and arranged
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to be cammed radially outwardly by the pipe section beinginserted to permit entrance thereof, and thereafter
snapping inwardly into interlocking relation by extending
into a valley between the corrugations of the male section
5 of pipe. Thereafter, the two pipe sections cannot be
separated by pulling upon them in opposite axial direc-
tions, except as a result of a separate intervening act.
Moreover, the latching elements are readily accessible
after connection so that the pi~e sections may be
separated again by lifting the la'ching elements out of
the valley, in the event it is necessary to do so.
Although the latching membe-s extend in~ardly a
substantial distance, the hinged support thereo~ permits
them to be cammed outwardly sufficiently to permit the
15 male portion of the pipe to move axially inwardl~ past the
latching members. Once the rib of the male sectior, passes
beyond the latching members, the latter automatically sn~p
inwardly into the adjacent valley to ef'ect ~ positive
interlocking relation which acts to prevent disconnection
2Q of the plpe sections.
When the two sections of the pipe are so con-
nected, the ends of the two smooth inner walls abut,
thereby providing a smooth continuous inner conduit which
will not interrupt or deflect the flow of fluid there
through. The connector is supported on the remainder of
the pipe by a frusto-conically annular collar which
engages and directs the male end of the entering section
of pipe so that the ends of the inner walls will align and
abut against each other.
Brief Description of the Drawinqs
A detailed description of one preferred embodi-
ment of the LARGE DIAMETER DO~BLE-WALLED PLASTIC PIPE and
method of making same is hereinafter described with speci-
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fic reference being made to the drawinss in which:
Fig. 1 is a longitudinal vertical sectional viewof a section of double-walled corrusa.e~ plastic pipe of
large diameter with a smooth interior wall as molded, pre-
paratory to cutting of same, as shown, ~o produce a sec-
tion of such pipe with a female connec~or at one end
thereof;
Fig. 2 is a longitudinal vertical sectional view
of primarily the coupling section OL' dOUb1e-Wa11ed
corrugated plastic pipe of large aime~er ~ith â smooth
interior wall as molded after ma~-,ns ~n- c~ throush its
corrugated wall around its la,chins ~le,_s~s and remo~7ins
the smooth interior wall from the coupli..- s~c.ion;
Fig. 3 is a longitudinal ver.icci ~ec.ional view
of the section shown in Fig. 1 after .he n-cessary cut or
cuts have been made to form two sections s- pipe, one with
a female connector at one of its en~s, c.~ ,he other with
a male end adapted to be inserte~ i c such a Lemale
connector, as shown at the left of ~ig.
Fig. 4 is a longitudinal verticl sectional view
of a section of plastic pipe having a female connector as
sho~n in Fig. 3, with the male end of G similar section
received within the female connector to efrectively and
automatically couple the same;
~5 Fig. 5 is a cross-sectional vie~ of the connector
end portion of the section of pipe shown in ~ig, 3 as
viewed from line 5-5 of Fig. 3;
Fig. 6 is a longitudinal vertical sectional view
of the portion of the mold which forms the connector por-
tion of the double-walled pipe, taken through the latch
element portion, as shown at line 6-6 o Pig~ 5;
Fig. 7 is a longitudinal vertical sectional view
of the same portion of the mold which forms the connector
portion of the pipe, taken longituàin~lly along a line
parallel to and circumferentially spaced from that as
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,
shown in Fig. 6, and reflecting the construction of the
pipe as seen along line 7-7 of Pig. 5;
Fig. 8 is a longitudinal vertical sectional view
illustrating the ca~ming action which takes place upon the
5 latching element of a connector portion of such a pipe
when a male section of similar pipe is inserted thereinto;
Fig. 9 is a longitudinal sectional view of the
two pipe sections shown in Fi~. 8 aft~r the ca~ing action
has been completed and the latch element has snapped into
10 locking position within the adjacent valley of the male
section, the base corrugation proile in the female end
res~rains the seal with the com?letec joint;
~ ig 10 is a longitudinal ver~ical sectional view
of a section of plastic pipe constituting a couplins
lS having a connector at each of its ends and adapted to
receive and couple thereto a male section of pipe in each
of its end; and
Fig. 11 is an en~ ele~ational vie~ of the prior
art illustrating how a pipe as heretofore formed must
deform to accommodâte another pipe section having fixed
locking tabs, in order to accomplish a connection there-
between.
Detailed Description of the Invention
~ s set forth hereinabove, in recent years a
definite need has arisen for double-walled plastic pipe
which are eight (8") inches or larger in diameter. In
order to have the required strength to meet industry stan-
dards, the walls of such pipe must be sufficiëntly thick
so that they are inflexible, rigid but elastic. When an
8" diameter plastic pipe is so constructed, it is esti-
mated ~hat approximately 50-80 lbs. of thrust is required
in order to cause plastic pipe havin~ fixed latching mem-
bers to be joined; the thrust to couple larger pipe
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-- 7
(larger than 8") with a fixed latching member is much
greater, with the required thrust to couple the pipe
sections increasing proportionally with the square of the
pipe diameter (that is, increases proportionally to D2).
Such a requirement is prohibitive When plastic pipe, such
as is shown in U.S. Patent 3,899,198, Maroschak, issued on
August 12, 1975, is constructed wi$h a wall sufficiently
thick to meet industry standards for an 8" or larger pipe,
it is impossible for the workers in the field to manually
lo join two pieces of pipe of such construction. This is
occasioned because, when the walls are made sufficiently
thick to provide the required strength, they are no longer
sufficiently flexible to permit such a joincler by means of
practical manual e~fort. Moreover, if such pipe were to be
manufactured with sufficient clearance to permit the
joinder of such pieces o~ pipe, then they would he readily
releasable as described in the Maroschak patent.
In addition to the above, there is a definite need
for such pipe to have two walls, the inner one of which is
smooth and the outer one of which is corxugated. The pipe
which is shown hereinabove in the drawings, and as will be
described hereinafter, is specifically designed to provide
such pipe which are not readily releasable when connected,
and which have latch members that are readily accessible
from the exterior so as to permit separation as a result of
a separate overt act, in the event such separation is
required.
The plastic pipe shown in Figs. 1-10, inclusive, are
preferably molded out of either high density polyethylene,
PVC or polypropylene. When high density polyethylene is
utilized, it is preferable to utilize a material having a
specific gravity of 0.955 + 0.005. The pipes shown in
Figs. 1-10, inclusive, are specifically designed to be 8"
in diameter or greater although, of course, they can be
manufactured at smaller diameters if desired. It is
imperative, however, that irrespective of the material from
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which these pipes are manufactured, that th~ir walls be
rigid and inflexible but elastic, so as to have the
strength required by the industry.
As shown, the pipe of Figs. 1-10, inclusive, can be
manufactured continuously by molding the same integrally.
By utilizing a few carefully selectecl cuts after molding,
such a continuous pipe can be readily cut into sections in
which one end portion functions as a female connector and
the other end portion functions as a male portion.
To meet the needs of the industry, the exterior wall
is corrugated while the interior wall is smooth. They are
molded integrally of either the same or thermally bondable
materials, preferably high density polyethylene. Thus, as
shown in Fig. 1, a continuous piece of double-walled pipe
15 may be molded by usiny the equipment, such as is
described in U.S. Patent 4,439,130, Dickhut et al, issued
on March 27, 1984. As shown, the major portion of such
pipe has an outer wall 16 which is corrugated and an inner
wall 17 which is smooth and continuous. The thickness of
the outer wall, as previously indicated, is sufficient to
be inflexible, rigid but elastic and preferably has a
thickness of 0.050" or more.
The outer wall 16 is characterized, in general, by
a plurality of corrugations 18, each of which has valley-
defining portions 19 which define the valleys 20therebetween. ~ach corrugation or rib 18 has a crown 21,
which, for pipes having a diameter of ~11 or more, are
preferably at least 11/16" wide. These crowns 21 may, of
course, have a greater width for pipes of diameter greater
than 8" and may be flat-topped as shown or may be of some
other configuration such as ridged or grooved.
The pipe 15 as molded is generally characterized by
a plurality of elongated sections 15a which may be
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identifie~ as male sectio~s r and which are connected by
relatively short female connector sections 15b, the latter
be1ng of slightly greater radius than the radius of the
corrugations 18 so that the male sections 15a may be
received therewithin after the proper cuts have been made.
It will be seen that the female section 15b is essentially
a sleeve constructed and arranged to receive the corrugat-
ed male sections 15a therewithin, to be locked thereto as
hereinafter described. This sleeve element lSb may or may
not have, as shown in Figs. 1-4, inclusive, a plurality of
relatively small annular corrugations 22 for strengthening
purposes.
Each of the female conneccor sections 15b is pro-
vided with preferably two to six e~ually circumferentially
spaced latch members 23, each disposed in the same trans-
verse plane. Each of these latch members is molded
integrally with the pipe 15 and is thereafter cut free
along each of its sides and at one of its ends, as at 24,
25 and 26 so that it becomes a lever which is free to
swing about its axis of pivot or fulcrum, indicated by the
broken line 27. This permits the latching member to swing
inwardly or outwardly, as the case may be, about the axis
of line 27 for latching and de-latching purposes.
Each of the latch members extends radially
inwardly toward the axis of the pipe lS and is charac-
terized by a substantially vertically extending latching
surface .28 and a camming surf~ce 29 which meet along a
transverse line 30. Side walls extend between these sur-
~aces to support same, as shown. The camming surface 29
extends at an angle of approximately 25 or greater to the
axis of the pipe L5, whereas the latching surface 28
approaches a more vertical relationship to that axis.
This can best be seen in ~ig. 3. The latch member extends
radially inwardly a distance of at least 25% of the depth
of one of the valleys 20 and preferably more, so as to
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provide a strong latching surface which. inc~eases in
latching ability in response to any effort to separate two
such sections when joined together, as shown in Fig: 3.
As best shown in Fig. 1, the female connec~or
section 15b is supported at each of its ends by one of a
pair of frusto-conically shaped collars 31, 32. The
larger end of each of the collars supports the sleeve
while the smaller end is connected to the en~ of one of
the valley-defining portions of the adjacent male section
15a. As will be described hereinafter, the collar 32 or
some portion thereof is subseauenLl.y cut free and
discarded, whereas the collar 31 is permitted to re~ain
intact to support the sleeve and its la,ching members 23.
This collar 31 has a definite additional function as
hereinafter described.
In order to provide a plurzli.ty of pipe sec.ions
each havins a relatively long male section 15a at one of
its ends and a relatively short female connector section
15b at its other end, we make a cut through the smooth
interior wall 17 at some point such as along the broken
line indicated by the numeral 33. It will be noted that
this cut is shown directly opposite the small end of the
collar 31 and is made only through the inner wall 17. One
or more additional cuts are made to remove a portion of
the collar 32 extending approximately from the broken line
34 through the bottom of the valle~1 adjacent the opposite
e~d of the connector section 15b to the broken line 35
through both the outer and inner walls 16 and 17, this cut
being essentially through the transverse plane which
passes through the larger end of the collar 32. When this
cut or cuts have bee~ completed, the result will be that
the portion of the tubing shown to the left of the cuts in
Fig. 1 will remain as a section of pipe with a male por-
tion at its left end and a female portion at its right
end. 5imilarly, the section shown at the right hand of
Fig. 1 will constitute a male portion which will have a
:~311~S2~
--11-- . .
female connector section (not shown) c2rried by its end a~
the right hand side of the view.
As a result of the cuts aescribed hereinabove, it
will be seen tha~ the inner wall 1l of e?ch such sec~ion
5 of pipe terminates in pproximately the same plane as the
small e~d o~ the collar 31. ~lso, the ~ner and outer
walls of the male section crea~ea by ~he cuts at the
right hand side of Fig~ 1 terminate at approximately the hot~
tom of .he last ~alley 20 of that sec'ior..
10 . Prepa-~tory ,o loininc t:~e ~,al^ s~ ic~ 1;2 with
the female conneotor 15b, 2 sas;{e. 36 ~ ch may be of
approximate circular cross-,ectional ccr.^igura ion, is
applied to .he end o' the male section l,z, as bes~ shown
in ~ig. 4. When the male sec~ion l~a is 1~ser.ed ,o the
15 posi,ion shown in ~ig. 4, the lat~h mem~c 23 will extend
into the valley 20 adjacen~ ..he end oI t~e section l5a and
the gasket 36 will perfect the seal ~e~eG.. .he end corru-
gation shape of the 15a sec.ion an~ ~h~ Jalley-Qefining
portio~s which support the female connec~or portion 15b.
2~ It will be see~ that the end of the inner wall 17 of the
~emale connector section 15b will then abut agains~ the
end of the inner wall which has been crea.ea by the cut 3
of the male section 15a.
It will be seen by reference to Fig. 4 that when
the male section 15a and fem~le connec,or 15b are so con-
nected, a latch member 23 extends .into the valley 20 to an
extent at least equal and prefer2~1y graa,er than 25% of
the depth of the valley. It is preIerable that the latch
member extend into the va}ley at le2st ;0~ of its depth,
as shown.
It will also be seen that the base oS latch
member 23 is disposed axially outwardly of the bottom of
the valley supporting the collar 31 a distance at least
substantially equal to 1.25 times the axial distance bet-
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5:~
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ween any two adjacent valley portions of the section 15a.
It will also be seen that the base of each latch rn~m~er is
loca.ed on the sleeve a distance from the pitch llne of
the valley adjacent to that latch member a aistance
substantially equal to 1.25 times the axial distance bet-
ween the pitch lines of a pair of such valleys.
Fig. 6 is a vertical sectional view of the mola
used to form the outer wall which becomes the connector
por~ion 15b, taken through one of the latch member~ 23.
Fig. 7 is a vertical sectional vie~ thrcush the
same mold that is shown in Fig. 6, but tc~en be~-een any
pair of la~ch members 23.
Figs. 8 and 9 illustrate on G lG~?er scal_ th~
camming action which takes place during .he joinder OI a
male section 15a with a female connec.or sec~ion l5b.
Fig. 8 shows the male section l5a bein~ r,rust inwardl~
into the female section 15b so that the latch ele~,len. 23
is being cammed radially outwardly by engGgement of itC
ca~ming surface 29 with a rib 18. It ~ill be seen tha.
the latching member is being forced raàially ou~wa~cly to
permit the crown of the male section 15a to pass
therewithin until the following valley 20 is Gisposed
directly inwardly of the latch member 23, at which point
the ~atch mem~er wil~ snap into the valley 20 in latc~ins
relationl as shown in Fig. 9. It will be seen that the
latching surface '28 extends more vertically and bears
against the valley-defining portion which defines the
valley 20. If desired, it is possible to insure reten.ion
of the latch members within the valley, ixrespective of
the magnitude of separation forces applied thereto, by
securing a belt or strapping 37 around the latch ~em~ers,
as shown in Fi~. 9.
Fig. 10 shows an alternative form of pipe which
can be molded so as to provide a female connector capable
of receiving at each of its opposite end~ (instead OI one)
~3~n~2~; .
a male section 15a. As shown, such a female connector
indicated by the numeral 40, will have a pair of oppo-
sitely facing ~atch elements 91 and 42 separated by one or
more valleys 4Oa. Each of ~he latch members 41 and 42 are
constructed identically to the latch members 23, except
that they are arranged so that their latching surfaces 43
and 4q face each other. They can be molded in the same
manner except that there is no requir~ment for an inner
wall, as will be readily unaerstood. It will De noted
that they are spaced from each c.her a~ approximate
distance of two or more valleys in such a ~ay that they
will ensa~e in the end vailey of each Ot ~he "a~e sections
15a and the ends of the smooth inner waiis o such male
sections and inner walls will abut, and ;:~e gaske~ 36 is
restrained between the male sections 15a. Such a connec-
tor element may have some utility w;~en il is desireQ to
connect , and or seal a pair of male sections 15a, as
shown in that figure.
Fig. 11 has been included ~e.el}~ to illustrate
the prior art and the manner in ~hich a piece OI plastic
pipe must be distorted when a fixed, rather than a pivo-
table, latch member is utilized. The latch members have
been indicated by the numeral 45 and the wall of the pipe
by the numeral 46. The broken line 47 indicates the shape
assumed by the walls of the pipe and shows the extent to
which the wall structure of the pipe 46 must be deformed
in order to effect a connection between two pieces of such
pipe, one of which has fixed latch members, such as indi-
cated by the numeral 45.
Wherever herein the phrase "rigid, inflexible but
elastic" or its substantial equivalent is utilizec, it is
intended to connote that the wall of the plastic pipe is
sufficiently rigid and inflexible so that, as a minimum,
it would be lmpossible to manually telescope two pieces of
such corrugated pipe, if one of them has fixed latch mem-
bers intended to effect a latched connection therebetween.
13~
~i4-
It also connotes that the w211s of the plastic pipe are of
sufficient thickness and rigidity to meet industry stan-
dard requirements for 8~l or larger diameter pipe.
Wherever herein the term "large diameter" is uti-
5 lized in reference to plastic pipe, it is intended toconnote plastic ~ipe havins an internal diameter of 8
inches, or greater.
Wh~n a male section I52 is connec~ed to a female
connector section 15b, as shown in Fig. 4, an eLfec,ive
lo an~ highly improve~ connection is oo.ained~ ~s the mal~
section 15a is inserted into the connec~or l;b, ~he
frusto-conical collar 31 is engaged by the end of sec~ion
15a and aligns and guides the same sc tha' the end~ of the
inner walls 17 come into abu.ting rela.ion as shown in
15 Fig. 4. It will be noted that ,he in~erior wall 17 cf the
two sections abut so as to provide 2 continuous an~
unobstructed conduit which will not tend to clo~ or to
contaminate the contents of the pipe as it passes there-
through.
The latch member 23 provides a highly efrec~ive
and efficient latching function which increases in its
locking capability as any attem~t is made to separate the
two sections after the connection has been made. Of equal
importance is the fact that the connection is obtained
easily and automatically by merely thrusting the male sec-
tion 15a into the female section 15b and the connection
can be accomplished without undue stress on the part of
the user. Moreover, the connection is normally non-
releasable, in contrast to plastic pipe which have hereto-
fore been manufactured with fixed latch members designeà
to be readily released. In addition, if it becomes
desirable to disconnect two such sections for any reason
whatever, this can be accomplisheâ by merely lifting each
of the latch members 23 radially outward, whereupon the
two pipe sections can be readily disconnected.
:~3~)S~6
-15-
It will, of course, be understood that various
changes may be made in the form, ~etcils, 2rrangement and
proportions of the parts withou, departing from the scope
of the invention which consists of the matter shown and
described herein and set forth in the ap~ended claims.
