Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF T~E INVENTION
With the advent of plastic pipe such as polyolefin and
other plastic materials, there has existed a need for connecting
lengths of pipe together to form a string of pipes. The use
of such plastic pipe has ranged from an inch or so in diameter
to as much as five feet.
The connecting together of such pipes has presented a
problem which is of particular significance in the field where
access to equipment and labor may be difficult. While fusion
of the pipe ends has been done for some time, this has generally
been somewhat laborious and expensive.
Various types of end connections have been devised requiring
clamps and auxiliary paraphernalia. One such device using
clamping is shown in the exterior pipe connector sleeve of
U.S. Patent No. 4,310,18~ in which the pipe ends are butted
together and clamped by the sleeve. This device and other
end clamps require extraneous parts with the danger of the
protruding clamp being accidentally struck and damaged by
external forces. For example, when joined strings of pipe
are pulled in a slip-lining construction job, it is particularly
desirable that the exterior of the pipe be completely flush
to enhance the pulling or pushing of the pipe along the ground
or through a large pipe to be repaired.
Further problems have been a tendency for connected ends
to pull apart while in service with consequent danlage to the
pipe line and environment and difficulty in location of the
break and repair.
SU~ARY OF T~E INVE~TION
By means of the instant invention there has been provided
a plastic pipe having an integral end connection which may
be joined with a like plastic pipe or a semi-rigid pipe having
a mating integral end connection. The adjacent pipes may
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be pushed together to mate the end connectors in a locking
engagement to resist any tendency to separate the joined pipe
ends.
The plastic pipe employed is desirably of a polyolefin
nature such as polyethylene, polypropylene or polybutylene
having semi-rigid characteristics but also having the ability
to flex or bend and expand and compress to a slight degree to
accommodate the interfit of the male and female end connections
of the pipe when press-fitted together. It will be understood
that other plastic pipes having similar characteristics may
also be used. The integral end connections may be formed
in the pipe when fabricated in the molding process or later
such as by machining or the like.
The structure of the end connection is in the nature
of one or more wedge shaped internal ribs and grooves formed
on the interior of the female member which interfit in locking
relation with one or more wedge shaped e~terior ribs and grooves
formed on the exterior of the male member. When the male
member is forceably pushed into the female member the latter
is slightly e~panded or distended while the male end may be
slightly compressed until the two members are mated together
at which time the female member contracts to its normal state
and the male member expands to its normal state to lock the
two members together and, through a wedge shaped interfit
of the ribs and grooves, resist separation forces.
The wedge shaped ribs and grooves may be in the form
of slanted or indented sides of the ribs and grooves which
underlie one another and resist any tendency to pull apart
when the ends are connected together. The wedge shaped
configuration may be on the sides of the ribs and grooves which
are engaged in the press-fit operation as well as the opposite
sides to provide the locking engagement. The wedge shaped
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configuration may be conveniently provided by a trapezoidal
shape or in the form of a mating bead and groove interfit
for the ribs and the grooves.
When a trapezoidal shape or the like is employed where
a pointed edge of a rib engages a groove corner in the press-
- fitting engagement, or where substantial forces of compression
or tension are otherwise encountered, the corners of the ribs
and grooves may be substantially rounded. This provides for
stress distribution and spreading of the force and pressure
to minimize any tendency to break or tear a rib in the press-
fitting operation or forces encountered in service which might
tend to separate the pipe.
The end ribs of both male and female members are slightly
bevelled or chamfered to facilitate the sliding of the male
member. To further ease this movement where a series of ribs
are employed, the end or outer ribs of both the male and female
members are wider than the corresponding end or outer grooves
to prevent premature locking of the ribs and grooves before
the members are fully engaged. This relationship enables the
end of the male member to ride past the end of the female
member until it approaches a shoulder stop of the female member
to provide proper registration of the ribs and grooves for
the final locking engagement.
The above features are objects of this invention. Further
objects will appear in the detailed description which follows
and will be otherwise apparent to those skilled in the art.
For purpose of illustration of this invention a preferred
embodiment and modifications thereof are shown and described
hereinbelow in the accompanying drawing. It is to be understood
that this is for the purpose of example only and that the
invention is not limited thereto.
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IN T~E DRAWINGS
Figure 1 is a view in axial section of the pipe having
the integral end lock connections before being joined;
Figure 2 is an enlarged view in a~ial section showing
the joined ends of the pipe;
Figure 3 is a further enlarged fragmentary view in axial
section similar to Figure 2 showing the interlocking connection
and having an additional rib and groove series;
Figure 4 is an enlarged view in axial section showing
the rib engagement with a rounded groove corner;
Figure 5 is a view similar to Figure 4 showing a modified
rib and groove corner construction;
Figure 6 is an enlarged exploded view in a~ial section
showing a superimposed connection with a further modified
rib and groove construction; and
Figure 7 is a schematic view on a reduced scale showing
a clamp and ram for forcing ends of the pipe together.
DESCRIPTION OF T~E INVENTION
The plastic pipe having the integral end connections
is generally illustrated by the reference numeral 10 in Figures
1-3 and 7. Each length of pipe is provided with a female
connection 12 and a male connection 14, although it will be
understood that where desired alternate pipes may have both
ends with male and female connections and that the pipes may
be fitted together in this fashion.
The plastic pipe is preferably polyethylene but other
polyolefin pipes, such as polypropylene and polybutylene,
having similar characteristics of being semi-rigid, the ability
to bend slightly along substantial lengths and having the
capacity to distend or contract slightly may be employed.
The pipes may range in diameter from about three inches to
over five feet and have a substantial wall thickness to withstand
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internal and external pressures and resistance to abrasion
when the pipes are moved along the ground in various types
of construction.
The integral female and male end connectors are formed
on the interior and exterior surface in the fabrication of
the pipe itself as in the molding process or by machining.
Each of the end connections has one or more ribs and grooves
which interfit with one another when the female and male end
connections are press-fitted together as will be more fully
described hereinbelow. When fitted and locked together the
joined pipes present a flush continuous internal and external
surface which reduces internal friction or resistance to fluid
flow on the interior and provides a smooth external surface
presenting no impediment or drag when moved along the ground
or through a pipe as in a slip-lining operation.
The female end connector 12 is comprised of an end or
outer wedge shaped rib 16 and an inner wedge shaped rib 18.
A first or outer wedge shaped groove ~0 separates the two
ribs while a second or interior wedge shaped groove 22 separates
the inner rib 18 from a stop shoulder 24 as best shown in
Figure 2. The sides of the wedge shaped grooves slant from
the perpendicular with the angle of the slant being, for example,
8D but it will be understood that the degree of the slant
may be varied as desired. Figure 3 shows a groove 25 separating
a second inner rib 27 from the stop shoulder 24. In order
to facilitate the joining or riding together of the female
and male end connections, -the end rib 16 has a bevelled or
chamfered surface 26 formed at the outer corner of the rib.
The male end connection 14 has ribs and grooves formed
in a similar fashion to that of the female end connection
12 but on the exterior of the pipe. Thus, the male end has
an end or outer wedge shaped rib 28 formed on the pipe along
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with a second or inner wedge shaped rib 30. A first or outer
wedge shaped groove 32 separates the two ribs while a second
or inner wedge shaped groove 33 separates the inner rib 30
from a stop shoulder 34. Figure 3 shows a groove 35 separating
a second inner rib 37 from the stop shoulder 34. A bevelled
or chamfered surface 36 is formed at the outer corner of the
male end connection which facilitates the joining together
of the end connections and distends or e~pands the female
end connection and compresses the male connection by the wedging
or camming action when the bevelled surfaces 26 and 36 of
the female and male end connections are pressed together.
In order to ensure that the ribs and grooves of the female
and male end connections do not prematurely engage until the
full joined connection is made, as shown in Figure 2, the end
or outer ribs 16 and 28 of the female and male end connections,
respectively, are constructed to be wider than the end grooves
20 and 32 of the female and male end connections, respectively.
This prevents engagement of the ribs in these grooves. Proper
engagement of the aforementioned end ribs 16 and 28 occurs
when the female and male end connections are completely pushed
together at which time engagement of the aforementioned ribs
16 and 28 occurs in the grooves 33 and 22, respectively, as
will be seen in Figure 2. Figure 3 shows the engagement of
ribs 16 and 28 with grooves 35 and 25, respectively. Similar
engagement of the inner ribs 18 and 30 of the female and male
end connections, of somewhat lesser width than the end ribs,
will take place in the outer grooves 32 and 20 of the male
and female end connections,respectively. It will be understood
that a slight tolerance is provided for the interfit of the
ribs in the mated relation in the grooves as will be well
understood in the art.
Where desired the tolerance may be eliminated and the
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ribs may be made slightly wider at the outside or end than
the mouth of the grooves with the registering exterior corners
of the ribs or grooves, or both, being chamfered, bevelled
or rounded. By this relationship a camming action may be
effected to force the slightly wider ribs into the grooves
by taking advantage of the slight resiliency of the polyolefin
pipe. This relationship also augments the wedging interlock
of the ribs in the grooves.
A locking relationship for the ribs and grooves when
the male and female end connections are joined is provided
for the ribs and the mating grooves through the wedge shaped
configuration and the opposed slanting sides of the ribs.
As best shown in Figures 2 and 3 the wedge shape is in the
form of a trapezoid but it will be understood that other wedge
shaped forms may be utilized in order to provide a locking
engagement. In the trapezoidal form the slanting sides of
the ribs and grooves which bear and mate against one another,
as shown in Figures 2 and 3, provide resistance to forces
such as by compression or tension tending to separate the
rib and groove engagement.
In order to reinforce the joined end connections when
coupled together, a reinforcing sleeve 38 as shown in Figures
1, 2 and 6 may be employed. The sleeve may for great strength
be of steel but it will be understood that other materials
such as polyethylene or the like may be employed. The sleeve
may be employed to improve the strength O r the coupled end
connections to withstand internal pressures up to the design
rating of the remainder of the pipe. As shown in Figures
1 and 6, the sleeve may be fitted snugly by a slidable friction
fit on the female end of the pipe 12, or on the male end 1~
as desired, slightly away from the end connection structure
and, after coupling, moved axially to cover the coupled end
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connections.
A modified wedge shaped rib and groove construction is
shown in Figure 6. In this form the wedge shaped ribs are
formed by a bead 40 at an exterior corner of the ribs which
is adapted to engage a slot or groove 42 at an interior corner
of a mating groove within the rib. This relationship when
the male and female ends are connected provides a wedging
and locking engagement. An additional feature of the bead
and groove engagement is provided by the rounded interfit
which effectively distributes stress at the interfitting corners
to distribute or diffuse force concentration in the region
due to press-fitting which might tend to break or tear the
ribs. While the bead 40 is shown at a leading exterior corner
of a rib of the male member 14 and a trailing interior corner
of a groove of the female member where the stress occurs,
it will be understood that this relationship may be reversed
and that the bead may be on a leading exterior corner of a
rib of the female member and that the groove may be at a trailing
interior corner of a groove of the male member. Both types
of relationships may also be utilized.
The trapezoidal shaped ribs and grooves may also be provided
with a feature to distribute stress or the interfitting corners o~
the ribs and grooves when press-fitted together or to withstand
compression or tension forces encountered during service.
It should be understood that when pressure or tension is placed
on the joined male and female end connections the exterior
corners of the trapezoidal wedge shaped ribs may exert great
force on the interfitting interior corners of the mating grooves.
In order to diffuse or distribute the force and prevent a
point-like concentration the interior corners of the grooves
are provided with a rounded shape 44 as shown in Figures 3
and 4. In order to maximize the force distribution the exterior
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corners of the ribs may likewise be rounded at 46 as shown
in Figure 5.
Where the forces encountered are compression forces such
as from the press-fitting of the male and female end connections
the rounded interior corners at the trailing interior corners
of the grooves and the leading e~terior corners of the ribs
need only be rounded. Where opposite or separation forces
may be encountered, such as by tension in pulling a string
of connected pipe lengths along the ground, the trailing exterior
corners of the ribs and the leading interior corners of the
grooves may be rounded, and it will be understood that one
or both the force conditions may be accommodated as desired
by rounding all the exterior corners of the ribs and all the
interior corners of the grooves.
As an actual example, the female and male end connections
may be formed in length of 20 to 40 feet of polyethylene pipe
having an outside diameter of 6.63 inches and an internal
diameter of 6.19 inches and a modulus of elasticity of 100,000
psi to 140,000 psi at room temperature. In the press-fitting
together of the female and male end connections an axial force
or 900 pounds to 1,100 pounds may be applied. Deformation
or distending of the female end connector and compression
of the male end to accommodate the interfit of the male member
as the respective ribs slide over one another until registering
engagement is effected is about 2%, well under an upper limit
of about 5%, which can be safely encountered before a permanent
distortion.
When the pipe is to be joined together, a gasket compound
or sealant such as that shown at 48 and 50 in Figure 3 may
be employed. This may be in the form of any conventional
sealant such as a flexible butyl rubber sealant or the like.
The sealant may also be used between the ribs and grooves
to fill the spaces therein to enhance the wedging and locking
action.
USE
The pipe of this invention with the integral end connections
is simply and easily connected together to provide a stable
and reliable locking engagement. This is of particular advantage
in the field where labor and equipment may be difficultly
accessible.
One method of joining the separate lengths together comprises
a clamp and press device, generally indicated by the reference
numeral 52 in Figure 6 may be employed. One pipe length 54
having a female end connection 12 integrated therein may be
clamped by the clamp 56 while another pipe length 58 having
a male end connection 14 is clamped in a moveable press clamp 56
powered by a hydraulic piston 62 or the like moveable in the
direction of the arrow. The pipe length 58 is moved toward
the pipe length 54 to insert the male end connection into
the female end connection until the complete locking interfit
shown in Figures 2 and 3 is obtained. A reverse arrangement
of the pipe lengths in the clamped press device may be employed
as will be readily understood.
Other means for joining may be employed which, per se,
form no part of this invention. In the field, hand winches
or come-a-longs, heavy construction equipment such as bulldozers,
back hoes and the like may be used to push one length of pipe
into another pipe which may be anchored or fixed against movement
in one fashion or another.
The pipe lengths may be joined in a string of pipe lengths
and pulled or pushed to any desired final location. The locked
joint when sealed with the flexible butyl rubber sealant assures
a water tight joint preventing both infiltration and exfiltration.
This is particularly beneficial where the corrosion, abrasion
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resistance and the flexibility of polyolefin pipe is needed.
The outside and inside surfaces are flush and of constant
diameter which enhances fluid flow and obviates external fittings
and protruberances which would cause problems in pulling the
pipe along the ground or in the interior of a larger pipe
to be repaired as in the case of slip-lining. Further, no
reduction in pipe size is required as where external clamps
are employed.
When joined, the locking interfit provided by the wedge
shaped ribs and interfitting grooves resist any tendency for
separation between the joined connections. The rounded corners
of the grooves and ribs further provide for effective stress
distribution to avoid rib damage or breakage in the press-fitting
joining operation or forces encountered in service after the
pipe ends have been connected. Where greater strength is required
to withstand high internal pressures, the reinforcing sleeve 38
may be simply employed by sliding it axially over the coupling.
While the end connections have been disclosed for both
the female and male end connections as being formed integrally
in plastic pipe for use with each other, it will be understood
that in some cases there may be a connection to a rigid steel
pipe or the like, equipped with mating ribs and grooves, as
at the terminal or start of a line or the like.
Various changes and modifications may be made within this
invention as will be apparent to those skilled in the art. Such
changes and modifications are within the scope and teaching
of this invention as defined in the claims appended hereto.
