Note: Descriptions are shown in the official language in which they were submitted.
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JOINT RESTRAINT
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a joint restraint
for connecting a pair of ax~-ally aligned pipes and/or
appurtenances such that a t__ght fit and suitable seal are
formed therebetween, and such that protection is provided
against the disengagement that could occur when force is
applied in the axial direct:Lon.
2. Description of Related Art
It is known to employ a joint restraint to prevent
disengagement of axially aligned pipes and/or
appurtenances. For purposes of this application, pipes
and/or appurtenances shall be referred to herein
collectively as "pipes" or in the singular as "pipe".
Typically, a joint restraint comprises an annular body
from which a plurality of evenly spaced wedge housings
axially extend. The annular body encircles the outer
surface of a first pipe, and is engaged therewith using
actuatable wedges held within each of the wedge housings.
The annular body is also connected to an integral flange
disposed at the terminus of a second pipe, so as to hold
the first and second pipes together.
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Examples of joint restraints, the pipes with which
they function and associated equipment may be found in
United States Patent No. 4,092,036 to Sato et al. ("Sato
'036"), United States Patent No. 5,071,175 to Kennedy, Jr.
("Kennedy '175"), and United States Patent No. 5,544,922
to Shumard et al. ("Shumard '922").
Joint restraints used in the past have suffered from
several disadvantages that have diminished their
functionality and ease of use, and that have resulted in
increased manufacturing costs. For example, many joint
restraints employed in the past required the use of sand
cores in casting the wedge housings. Because the use of
such sand cores increases processing time and expense, it
is desirable to employ a design that minimizes or
eliminates the need for such sand cores.
Another disadvantage of joint restraints employed in
the past is diminished or unpredictable performance with
plastic pipe (e.g., PVC). Many joint restraints rely on
friction between a gripping surface or mechanism such as
wedges, wedge rings and serrated split rings and the pipe
surface to secure the pipe. However, the behavior of such
friction-based means is unpredictable when used with PVC,
and the friction force that may be induced is limited.
The Kennedy '175 joint restraint addresses this
problem by employing a wedge having pipe-engaging teeth
that may be driven into engagement with the pipe surface.
The Kennedy '175 joint restraint, however, has several
disadvantages. Specifically, the design requires the use
of sand cores in casting, the design lacks a reliable
method of keeping the wedge in place and the wedge does
not retract when the actuating screw is retracted.
The Kennedy '175 disclosure contemplates the use of a
twist-off bolt to reduce the possibility of preventing the
wedge from being over-torqued during initial actuation.
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Ideally, however, the wedge itself should resist further
intrusion into the pipe sur:=ace after the initial
actuation groove is formed.
Another disadvantage of conventional joint restraints
is their lack of flexibility. For example, in the Kennedy
'175 patent, once the joint restraint is installed on the
pipe, the position of the wedges is fixed, other than a
relatively minor amount of radial play, with respect to
their respective wedge hous_Lngs. It is desirable to allow
the wedges some freedom to rnove within their respective
housings independently of the joint restraint in order to
increase the capacity of the system to accommodate joint
deflection resulting from settlement or other force on the
pipes. Likewise, it is advantageous to allow some play in
the radial displacement of an installed wedge in order to
accommodate greater variations in pipe size without the
need for shims or spacers.
Yet another disadvantage of conventional joint
restraints is the typical lack of means for retaining
wedges or other restraint means in their respective
housings prior to installation in the field. Such
retaining means are desirab:Le in order to allow
preassembly of wedges into a joint restraint, and to
reduce the likelihood of subsequent wedge loss.
A need exists, therefore, for a simple and robust
joint restraint that provides reliable restraint, that
minimizes the use of cores in molding, that is easy to
assemble, install and use, and that is multi-functional
and flexible with respect to pipe size and type. Such a
device should also provide a mechanism for retaining
wedges in their housings prior to or after installation.
SUMMARY OF' THE INVENTION
The apparatus of the present invention overcomes the
above-mentioned disadvantages and drawbacks which are
characteristic of the related art.
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The invention in one aspect provides a joint
restraint for restraining the junction between a first
pipe and a second pipe, wherein said joint restraint
comprises: (a) a substantially annular body; (b) a
wedge housing extending axially from said annular body,
said wedge housing comprising a front wall, a top wall
extending from said front wall, and at least one side
wall connected to said front and top walls, said at
least one side wall together with said front wall
defining a bottom opening opposite said top wall, and
said at least one side wall together with said top wall
defining a rear opening opposite said front wall,
wherein said top wall has a hole opening into said
wedge housing; (c) a bolt having an end; (d)means for
engaging said bolt within said hole in said top wall of
said wedge housing; and (e) a wedge disposed within
said wedge housing, said wedge comprising a front
surface, a rear surface, a top surface and a bottom
surface, said wedge further comprising at least one
tooth extending from said bottom surface; wherein said
front surface of said wedge is adjacent said front wall
of said wedge housing, said top surface of said wedge
is adjacent said top wall of said wedge housing, and
said end of said bolt is adjacent said top surface.
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In a preferred embodiment, the joint restraint of the
present invention comprises an annular body having a
plurality of axially extending wedge housings. The
annular body is adapted to encircle and engage the end of
a first pipe, and to connect to the terminal flange of a
second pipe in the manner contemplated by the Sato '036
and Kennedy '175 patents. In a preferred embodiment, the
wedge housings are uniformly distributed around the
annular body and each wedge housing defines a pocket
adapted to receive a bolt and a wedge.
In a preferred embodiment, the pocket defined by the
wedge.housing has no radially inner surface, being bounded
instead by the outer surface of the first pipe when
installed. In a preferred embodiment, the wedge pocket
face opposite the annular extension is also open, allowing
for coreless casting of the wedge housings.
In a preferred embodiment, a bolt hole passes through
the radially outer wall of the wedge pocket. During
actuation, the bolt is inserted through the hole, into the
wedge pocket and towards the pipe. Preferably, the hole
and bolt are threaded so that the bolt may be threadedly
engaged within the bolt hole. The wedge, which is
disposed between the end of the bolt and the pipe surface,
is thus acted upon by the bolt.
Each wedge comprises a radially outer top surface, a
front surface which faces into the pocket, an opposite
rear surface, two side surfaces, and a bottom surface.
The top surface of the wedge is adapted to receive the end
of the bolt. Preferably, a groove is disposed in the top
surface of the wedge and is adapted to receive the end of
the bolt. The groove preferably inclines with respect to
the bottom surface from the rear surface to the front
surface of the wedge. As the end of the bolt moves from
the rear surface to the front surface of the wedge, the
wedge exerts an increasing grip on the pipe. The
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orientation of the groove is such that, in an initial set
position, the groove at the rear surface of the wedge is
radially closer to the pipe surface than the groove at the
front surface of the wedge.
5 In a preferred embodiment, the bottom surface of the
wedge is curved to correspond to the curvature of the
outer surface of the pipe, and comprises two parallel
pipe-engaging teeth. The first tooth is disposed below
the groove and is adapted to penetrate the pipe surface
upon initial actuation of the wedge.
In a preferred embodiment, the second tooth is
disposed between the first tooth and the front of the
wedge. The second tooth is larger than the first, and
only penetrates the pipe surface after pressurization=.
Although the second tooth may contact the pipe surface
before the first tooth during actuation, the second tooth
does not penetrate the pipe surface. Instead, the wedge
rotates to focus penetrating force at the first tooth.
In a preferred embodiment, a tapered portion at the
bottom of the wedge extends from the first tooth to the
rear surface of the wedge and acts as a large bearing area
when the bolt operates upon the wedge. The bearing is
seated against the pipe surface when the first tooth is
fully embedded, and provides resistance to further torque
on the bolt by distributing the load over a large surface.
Once the wedge is actuated, motion of the first pipe
away from the second pipe causes the first pipe to shift
relative to the annular body. This is because the
connection between the annular body and the flanged end of
the second pipe is relatively rigid. The wedge, on the
other hand, has a tooth that is embedded in the first
pipe, and accordingly tends to travel with the first pipe.
As a result, the bolt and annular body slide forward
relative to the groove in the wedge.
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Forward motion of the bolt in the groove causes the
wedge to pivot about the embedded first tooth, and, with
sufficient force, causes the larger second tooth to
penetrate the pipe surface. When the bolt reaches the
front edge of the groove, further motion of the pipe is
prevented by interference between the front edge and the
bolt. In a preferred embodiment, the interference contact
area is increased by adding a raised lip at the front edge
of the groove. The raised lip also prevents the wedge
from rotating out from under the bolt at high thrust
forces.
In a preferred embodiment, retaining means are
employed to allow wedges to be held within their
respective wedge housings prior to installation. 'The
retaining means preferably comprise a shroud which forms a
partial shell around the wedge. The retaining means also
preferably hold the wedge in the proper location relative
to the bolt regardless of the location of the bolt hole or
the deflection of the joint between the first pipe and the
second pipe.
In a preferred embodiment, the shroud is secured to
the wedge by hooking upturned edges around flanges
disposed on the side surfaces of the wedge. In another
preferred embodiment, the shroud is secured to the wedge
by inserting the upturned edges into grooves disposed on
the side surfaces of the wedge. In each of these
embodiments, an aperture disposed in the shroud above the
groove of the wedge is then disposed on the end of the
bolt. The shroud is designed to deform during actuation
and operation of the joint restraint, in order to allow
rotation and displacement of the wedge.
In another preferred embodiment, the bottoms of the
sidewalls of the wedge housing pockets closest to the pipe
have projections or grooves in the pocket area. In this
embodiment, the shroud engages the projections or grooves
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to maintain the position of the wedge in the wedge housing
pockets.
In still another preferred embodiment of the present
invention, the end of the bolt is engaged with the wedge
to keep the wedge from coming out of the open back of the
pocket. Also a mechanism may be incorporated into the
shroud that allows the wedge to spring back into the
pocket when the joint restraint is removed from the pipe.
In still another embodiment of the present invention,
the shroud is engaged with the wedge, extends within the
wedge housing pocket and has a portion that extends out of
the wedge pocket and engages with the annular body to
maintain the wedge in the wedge pocket.
In a still further embodiment of the present
invention, a groove is disposed in the bottom of the
wedges and a ring is placed within each groove that
interacts with walls of the wedge pocket to maintain each
wedge in the wedge pocket.
Numerous objects, features and advantages of the
present invention will be readily apparent to those of
ordinary skill in the art upon a reading of the following
detailed description of presently preferred, but
nonetheless illustrative, erabodiments of the present
invention when taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPT_CON OF THE DRAWINGS
FIG. 1 is a perspective view of a joint restraint
according to the present invention;
FIG. 2 is an exploded perspective view of a wedge and
a wedge housing according to the present invention;
FIG. 3 is a section view of the joint restraint shown
in FIG. 1 prior to actuation;
FIG. 4 is a section view of the joint restraint shown
in FIG. 1 during actuation;
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FIG. 5 is a section view of the joint restraint shown
in FIG. 1 subsequent to actuation;
FIG. 6 is a section view of the joint restraint shown
in FIG. 1 after pressurization;
FIG. 7 is a section view of the joint restraint shown
in FIG. 1 at high pressure;
FIG. 8 is a section view of a wedge and shroud
according to the present invention;
FIG. 9 is a top plan view of a shroud according to
the present invention;
FIG. 10 is a section view of an alternate wedge and
shroud according to the present invention;
FIG. 11 is a cross section view of an alternate bolt
according to the present invention; and
FIG. 12 is a cross section view of another alternate
bolt according to the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings, and particularly to
FIGS. 1 and 2, a preferred embodiment of the joint
restraint of the present invention is shown and generally
designated by the reference numeral 10.
In a preferred embodiment, the joint restraint 10 is
disposed on a first pipe 12 and comprises an annular body
14 through which the first pipe 12 passes and from which
an annular projection 16 and a plurality of wedge housings
18 extend. A plurality of through holes 20 pass through
the annular body 14 and are adapted to receive bolts
extending from the flanged terminus of a second pipe (not
shown) in the manner contemplated by the Sato '036 and
Kennedy '175 patents.
In a preferred embodiment, the wedge housings 18 are
uniformly distributed around the annular body 14 and the
joint restraint 10 is installed such that the wedge
housings 18 extend away from the end 22 of the first pipe
12.
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Each wedge housing 18 comprises a top wall 24, two
side walls 26, and a front wall 28. The top wall 24 is
the radially outer wall of the wedge housing 18 and the
front wall 28 is the wall closest to the end 22 of the
first pipe 12. The top wall 24 of each wedge housing 18
comprises a hole 30 adapted to receive a bolt 32. In a
preferred embodiment and as shown in FIG. 2, the hole 30
and bolt 32 are threaded so that bolt 32 may be threadedly
engaged within hole 30.
Each wedge housing 18 defines a wedge pocket 34
characterized by an open bottom 36 opposite the top wall
24 an(;l an open rear face 38 opposite the front wall 28.
The use of an open rear face 38 rather than a rear wall
allows the wedge housings 1B of the present invention to
be cast without using cores.
Each wedge pocket 34 is adapted to receive a wedge
40. The wedge 40 is held within the wedge pocket 34 such
that when the joint restraint 10 is installed, the bottom
42 of the wedge 40 faces toward the outer surface 56 of
the first pipe 12, the top 44 of the wedge 40 faces the
top wall 24 of the wedge ho'using 18, the front surface 46
of the wedge 40 faces the front wall 28 of the wedge
housing 18 and the rear surface 47 of the wedge is
opposite the front surface 46.
The top 44 of the wedge comprises a groove 48 adapted
to slidably receive the end 50 of the bolt 32.
Preferably, the groove 48 has a slope that inclines from
the rear surface 47 to the front surface 46 of the wedge
40. In another preferred einbodiment, the end 50 of the
bolt 32 is flat-bottomed and in still other preferred
embodiments suitable for high pressure service, the groove
48 has a slope as noted above and the end 50 of the bolt
32 is conical and preferably has a profile corresponding
to the slope of the groove 48.
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The bottom 42 of the wedge 40 comprises two pipe-
engaging teeth 52 and 54, and in a preferred embodiment,
both the bottom 42 and the teeth 52 and 54 are curved or
arcuate to conform to the curvature of the surface 56 of
5 the first pipe 12. In a preferred embodiment, the first
tooth 52 is disposed below the groove 48. The second
tooth 54 extends for a greater distance from the bottom 42
of the wedge 40 than the first tooth 52, and is disposed
between the first tooth 52 and the front 46 of the wedge
10 40.
In a preferred embodiment, a shroud 60, shown in
FIGS. 3-9, is employed to hold the wedges 40 in their
respective wedge housings 18 and in the proper actuation
location prior to installation of the joint restraint 10
on a pipe 12. The shroud 60 preferably comprises a
suitable material that allows the shroud 60 to snap fit as
described below, and in order to allow flexing during
actuation and operation of the joint restraint.
In a preferred embodiment, the shroud 60 forms a
shell around the top 44 and sidewalls 62 of the wedge 40.
As shown in FIGS. 8 and 9, the shroud 60 comprises
upturned portions 64 and is secured to the wedge 40 by
snapping the upturned portions around flanges 66 extending
from the sidewalls 62 of the wedge 40. In an alternate
embodiment and as shown in FIG. 10, the shroud 60 is
secured to the wedge 40 by snapping the upturned portions
64 into grooves 67 disposed in the sidewalls 62 of the
wedge 40.
In a preferred embodiment, the top surface 68 of the
shroud 60 comprises an aperture 70 into which the end 50
of the bolt 32 may be threaded. Alternatively, as shown
in FIG. 11, the bolt 32 may comprise a receiving groove 72
around which the aperture 70 of the shroud 60 snaps. In
another alternate embodiment and as shown in FIG. 12, the
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bolt 32 may comprise a flange 73 over which the aperture
70 of the shroud 60 is passed.
In addition, in a manner similar to that disclosed in
Shumard '922, the bottoms of the sidewalls of the wedge
housing pockets closest to the pipe have projections or
grooves in the pocket area. In this embodiment, the
shroud engages the projections or grooves to maintain the
wedge in the wedge pocket.
In another preferred ernbodiment of the present
invention, the end of the bolt is engaged with the wedge
to keep the wedge from coming out of the open back of the
wedge pocket. Also a mechanism may be incorporated.into
the shroud that allows the wedge to spring back into the
joint restraint when the jo:Lnt restraint is removed from
the pipe.
In still another embodiment of the present invention,
the shroud is engaged with the wedge, extends within the
wedge housing pocket and has a portion that extends out of
the wedge pocket and engages with the annular body to
maintain the wedge in the wedge pocket.
In a still further embodiment of the present
invention, a groove is disposed in the bottom of the
wedges and a ring is placed within each groove that
interacts with the walls of the wedge pocket to maintain
each wedge in each wedge pocket.
Installation of the joint restraint 10 of the present
invention comprises the actuation sequence shown in FIGS.
3-5. For initial actuation, shown in FIG. 3, the threaded
bolt 32 is rotated or torqued into the wedge pocket 34
such that the end 50 of the bolt 32 moves radially inward
towards the pipe surface 56 and is received within the
groove 48 in the top 44 of the wedge 40.
As shown in FIG. 4, continued rotation or torquing of
the bolt 32 drives the wedge 40 towards the pipe surface
56 such that the wedge 40 is eventually disposed between
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and in contact with the end 50 of the bolt 32 and the pipe
surface 56. The shroud 60 travels towards the pipe
surface 56 with the bolt 32 and wedge 40. As shown in
FIG. 5, with continued rotation or torquing of the bolt
32, the first tooth 52 is driven into and penetrates the
pipe surface 56.
The second tooth 54 does not penetrate the pipe
surface 56 during initial actuation because the force of
the bolt 32 on the wedge 40 causes the wedge to pivot
about an axis defined by the tooth 52 so that the bottom
surface 42 of the wedge 40 between the first tooth 52 and
the rear surface of the wedge 40 contacts the pipe surface
56. If the second tooth 54 contacts the pipe surface 56
before the first tooth 52, as shown in FIG. 4, continued
rotation or torquing of the bolt 32 will cause the wedge
50 to rotate or pivot about the second tooth 54 until the
first tooth 52 contacts the pipe surface 56. Preferably,
the shroud 60 adapts to permit such rotation or pivoting
to occur.
In a preferred embodimernt of the present invention,
the bottom surface 42 of the wedge 40 is tapered between
the first tooth 52 and the rear surface 74 of the wedge 40
in order to form a bearing 76 that dissipates the
actuation load of the bolt 32 on the wedge 40 over a
relatively large area. After the first tooth 52 is fully
embedded in the pipe surface 56, the bearing 76 is seated
against the pipe surface 56 such that over-torquing does
not result in penetration of the second tooth 54 into the
pipe surface 56.
Those of ordinary skill in the art will recognize
that the protection provided by the bearing 76 may be
supplemented by using a torque wrench. Proper torquing
and convenient installation of the wedge assemblies may
also be ensured by providing a nut designed to shear at a
predetermined torque (a "twist-off" nut).
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An alternate bolt 84 employing a twist-off nut 86 is
shown in FIG. 11. The twist-off nut 86 of the alternate
bolt 84 can be identical in structure and operation to the
twist-off nut disclosed in United States Patent No.
4,627,774 to Bradley, with one exception: in the
present invention, the thrust collar comprised by the
Bradley device is unnecessary and is omitted.
Once the wedge 40 is actuated, motion of the first
pipe 12 away from the second pipe, as occurs upon
pressurization or other separation force, causes the first
pipe 12 to shift relative to the annular body 14 and the
bolt 32. The sequence is shown in FIGS. 5-7.
The connection between the annular body 14 and the
flanged end of the second pipe is relatively rigid. As a
result, the second pipe, annular body 14, bolt 32, and
wedge housing 18 remain substantially stationary with
respect to one another within the rated pressure of the
joint restraint 10. The wedge 40, on the other hand, is
embedded in the first pipe surface 56, and accordingly
tends to travel with the first pipe 12.
As the wedge 40 begins to move with the pipe 12, it
slides with respect to the stationary bolt 32, such that
the bolt 32 moves relative to the groove 48 toward the
front of the wedge 40, as shown in FIG. 6. The groove 48
is adapted to permit such relative ntotion within a certain
range. Since the position of the bolt 32 is fixed, the
sliding of the wedge 40 beneath the bolt 32 causes
pivoting of the wedge 50 about the embedded first tooth
52, especially in the preferred embodiment in which the
groove 48 has an upward slope. As a result, the second
tooth 54 is driven into the pipe surface 56.
After the second tooth 54 is embedded in the pipe
surface, further pivoting of the wedge 40 is inhibited,
but the wedge 40 may still slide relative to the bolt 32
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until interference with the front edge 78 of the groove 48
prevents further motion.
In a preferred embodiment, the front edge 78 of the
groove 48 may comprise a raised lip 80 (shown in FIG. 8)
to increase the contact area with the bolt 32, and, as is
shown in FIGS. 8 and 9, the shroud 60 may comprise an arch
82 adapted to accommodate the raised lip 80.
Those of ordinary skill in the art will recognize
that the joint restraint described above and shown in
FIGS. 1-12 can be used in many other applications. For
instance the joint restraint of the present invention can
be used in conjunction with a plain ring to restrain a
push-on joint in which the two rings are joined by
connecting bolts. This type of application is similar to
that disclosed in U.S. Patent No. 4,336,959.
The joint restraint of the present invention can also
be used in connection with a flanged pipe joint.
Typically such flanges are fabricated as a part of the
pipe. It is advantageous, at times, to cut pipe at a job
location and be able to connect and restrain plain end
pipe to a flange. The joint restraint of the present
invention can be used to restrain this type of flange
adapter in a manner similar to that described in U.S.
Patent No. 4,372,587.
While preferred embodiments of the invention have
been shown and described, it will be understood by persons
skilled in the art that various changes and modifications
may be made without departing from the spirit and scope of
the invention which is defined by the following claims.
