U.S. patent application number 11/408298 was filed with the patent office on 2007-10-25 for method of producing helically corrugated metal pipe and related pipe construction.
Invention is credited to James C. Schluter, William L. Zepp.
Application Number | 20070245789 11/408298 |
Document ID | / |
Family ID | 38618176 |
Filed Date | 2007-10-25 |
United States Patent
Application |
20070245789 |
Kind Code |
A1 |
Zepp; William L. ; et
al. |
October 25, 2007 |
Method of producing helically corrugated metal pipe and related
pipe construction
Abstract
A pipe manufacturing device and method provides for pipe
diameter monitoring and responsive pipe diameter control. Various
pipe configurations and pipe assemblies adapted for ease of in the
field connection are also provided.
Inventors: |
Zepp; William L.; (Lebanon,
OH) ; Schluter; James C.; (Franklin, OH) |
Correspondence
Address: |
THOMPSON HINE L.L.P.;Intellectual Property Group
P.O. BOX 8801
DAYTON
OH
45401-8801
US
|
Family ID: |
38618176 |
Appl. No.: |
11/408298 |
Filed: |
April 21, 2006 |
Current U.S.
Class: |
72/49 |
Current CPC
Class: |
B21C 37/124 20130101;
B21C 37/121 20130101; B21C 37/128 20130101; B21C 37/122 20130101;
B21C 37/126 20130101; B21C 37/127 20130101 |
Class at
Publication: |
072/049 |
International
Class: |
B21C 37/12 20060101
B21C037/12 |
Claims
1-11. (canceled)
12. A method of manufacturing helically corrugated metal pipe,
comprising the steps of: (a) drawing a metal sheet off of a coil;
(b) corrugating the metal sheet to produce a corrugated metal
strip; (c) spiraling the corrugated metal strip and joining
adjacent edges of the spiraled corrugated metal strip in a crimped
manner to produce a helical seam; (d) automatically monitoring
diameter variations of pipe being produced; (e) based upon the
diameter monitoring, automatically varying pipe diameter in a
manner to produce a pipe segment having a first end with a diameter
that is larger than a diameter of a second end; (f) working the
first end to produce a substantially corrugation free bell end, and
working the second end to produce a spigot end with an annular
gasket seat.
13. The method of claim 12 wherein step (e) involves varying helix
angle of the pipe segment along a length of the pipe.
14. The method of claim 12 wherein the bell end is produced with a
entry lip that angles outward.
15. The method of claim 12 wherein step (f) includes forming one or
more annular corrugations adjacent the substantially corrugation
free bell end.
16. A method of manufacturing helically corrugated metal pipe,
comprising the steps of: (a) drawing a metal sheet off of a coil;
(b) corrugating the metal sheet to produce a corrugated metal
strip; (c) spiraling the corrugated metal strip and joining
adjacent edges of the spiraled corrugated metal strip to produce a
helical seam; (d) automatically monitoring diameter of pipe being
produced; (e) based upon the diameter monitoring, automatically
varying pipe diameter; (f) producing multiple pipe segments by
cutting the helically corrugated metal pipe each time a specified
length of pipe is produced; (g) coordinating the pipe diameter
variations of step (e) with the cutting operations of step (f) such
that pipe segments are produced in the following sequence in a
repeating manner: (1) producing a pipe segment having a downstream
end and an upstream end, a diameter of the upstream end larger than
a diameter of the downstream end, then (2) producing a pipe segment
having a downstream end and an upstream end, a diameter of the
upstream end smaller than a diameter of the downstream end.
17. The method of claim 16 wherein the diameter of the upstream end
of each pipe segment of (g)(1) is substantially the same as the
diameter of the downstream end of each pipe segment of (g)(2).
18. The method of claim 16 wherein, for each pipe segment of
(g)(1), the upstream end is worked to produce a substantially
corrugation free bell end, and the downstream end is worked to
produce a spigot end with at least one annular corrugation.
19. The method of claim 16 wherein, for each pipe segment of
(g)(2), the downstream end is worked to produce a substantially
corrugation free bell end, and the upstream end is worked to
produce a spigot end with annular corrugations.
20-36. (canceled)
37. A helically corrugated metal pipe assembly adapted for
facilitating end-to-end connection in the field, comprising: a
tubular structure in the form of a spiraled corrugated metal strip
with opposite side edges adjacent each other and joined together to
form a helical seam along a length of the tubular structure, a
central region of the tubular structure helically corrugated, a
first end of the tubular structure worked to provide an annular
structure, a bell fitting positioned on the first end of the
tubular structure and having an end portion, shrink wrap material
wrapped about the pipe assembly in a region to cover the annular
structure and the end portion of the bell fitting, the shrink wrap
heated to form fit to the pipe assembly thereby securing the bell
fitting on the end of the tubular structure and providing a sealing
function between the tubular structure and the bell fitting.
38. The helically corrugated metal pipe assembly of claim 37
wherein the annular structure is an annular gasket seat with an
annular gasket therein, wherein the end portion of the bell fitting
engages the annular gasket.
39. The helically corrugated metal pipe assembly of claim 37
wherein a second end of the tubular structure includes an annular
gasket seat.
Description
TECHNICAL FIELD
[0001] This application relates generally to helically corrugated
metal pipe commonly used in drainage applications and, more
specifically, to a method of producing such pipe with improved
diameter control and/or end connection features.
BACKGROUND
[0002] The standard production process for producing helically
corrugated metal pipe is well known and involves first forming
lengthwise corrugations in an elongated strip of sheet metal, with
the corrugations extending along the length of the strip. The
corrugated strip is then spiraled into a helical form so that
opposite edges of the corrugated strip come together and can be
either crimped or welded to form a helical lock along the pipe.
Diameter control of the resulting pipe is regularly an issue in the
manufacturing process and is important to the functionality of the
pipe from an installation standpoint when pipes are being connected
end to end at a job site in the field. Attempts to address diameter
control have been made in the past. U.S. Pat. Nos. 3,940,962,
3,417,587, 4,287,739 and 4,438,643 describe pipe manufacturing
techniques and related equipment. Improvements are continually
sought.
[0003] Joining lengths of helically corrugated metal pipe creates
issues in the field. U.S. Pat. No. 5,842,727 teaches a coupling
member that can be used to join the ends of two pipes in a sealed
manner. Improvements in the area of pipe coupling would be
advantageous as the same could reduce pipe installation costs.
SUMMARY
[0004] A system and method for pipe size or diameter control in
connection with the production if helically corrugated pipe is
provided. Advantageous pipe configurations may be achieved. Pipe
size monitoring and control may be automated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a top plan schematic of a pipe manufacturing
device;
[0006] FIG. 2 is a cross-section of an exemplary corrugated metal
strip taken along line 2-2 of FIG. 1;
[0007] FIG. 3 is an exemplary cross-section of a lockseam;
[0008] FIG. 4 is an exemplary control system configuration for the
device of FIG. 1;
[0009] FIG. 5 shows exemplary pipe with unitary bell end and
unitary spigot end;
[0010] FIG. 6 shows a spigot end of one pipe within a bell end of
another pipe;
[0011] FIG. 7 depicts exemplary pipe diameter profiles;
[0012] FIGS. 8 and 9 illustrate an exemplary pressure roller and
drive assembly;
[0013] FIG. 10 illustrates an exemplary pipe diameter monitoring
device;
[0014] FIG. 11 is a schematic illustration showing a pair of
lockseam rollers and a pressure roller;
[0015] FIG. 12 is a schematic depiction of a pipe having a larger
diameter end and a smaller diameter end; and
[0016] FIG. 13 is a schematic depiction of another embodiment of a
pipe assembly.
DETAILED DESCRIPTION
[0017] Referring to FIG. 1, a pipe manufacturing line or device 10
is shown in top plan schematic form. The device 10 includes a
decoiler unit 12 for receiving a coil 14 formed by a rolled metal
sheet. The illustrated decoiler unit 12 supports the coil 14 on a
rotatable expansion mandrel 16, permitting the coil to rotate
during pipe manufacture. A weld table 18 is shown downstream of the
decoiler unit 12 and is provided for welding the end of one metal
sheet to the end of the metal sheet of a different coil upon coil
replacement. A corrugating line 20 includes a number of corrugators
22 for drawing the metal sheet off of the coil 14 and placing
corrugations in the metal sheet to produce a corrugated metal strip
24. The metal sheet passes between upper and lower corrugating
rollers in each of the corrugators 22 and the rollers apply
pressure to the sheet to form corrugations. By way of example,
first corrugator 22 may form a middle corrugation in the strip,
next corrugator 22 may form second and third corrugations alongside
the previously formed middle corrugation, next corrugator 22 may
form fourth and fifth corrugations alongside the previously formed
second and third corrugations, and so on, with the number of
corrugators varying as necessary. However, variations on the
operation of the corrugators are possible. The corrugations may be
of any suitable shape and configuration. In one embodiment, the
pipe manufacturing device operates to produce hydraulically
efficient pipe such as that described in U.S. Pat. No. 4,838,317,
in which case the corrugated metal strip may have a cross-section
similar to that generally shown in FIG. 2, where the corrugations
11 are shown with a generally rectangular or box-shape and the side
edges of the corrugate metal strip 24 includes respective lips 13
and 15 for use in producing the helical lockseam described below.
The exact configuration of locking lips 13 and 15 can vary.
[0018] The rollers of the illustrated corrugators 22 are driven by
an electric motor 26 with its output linked to a
gearbox/transmission arrangement 28. A forming head 30 is
positioned to receive the corrugated metal strip 24 and includes a
lockseam mechanism 32 located at a pipe exit side 34 of the forming
head. The forming head 30 may be a well known three-roll forming
head configured to spiral the corrugated metal strip 24. The
lockseam mechanism 32 locks adjacent edges of the spiraled
corrugated metal strip in a crimped manner to produce a helical
lockseam 100 in the resulting pipe 102. Specifically, as the
corrugated metal strip is helically curved back upon itself to form
the pipe-shape, the locking lips 13 and 15 come together before
passing into the lockseam mechanism 32, and the lockseam mechanism
32 presses the lips together to produce a lockseam that may, in one
example, have the general appearance of that shown in the
cross-section of FIG. 3. Referring to FIG. 11, in one embodiment
the lockseam mechanism 32 is formed by an upper lockseam roller 104
and a lower lockseam roller 106. The engaged locking lips 13 and 15
of the spiraled strip pass between these rollers where the crimping
operation is performed. As an alternative to the lockseam
mechanism, a weldseam mechanism could be provided to join adjacent
edges of the strip to form a helical weldseam.
[0019] Referring back to FIG. 1, a saw unit 36 is positioned along
the pipe exit path and includes a saw 38 that is movable into and
out of engagement with the pipe 102 and that is also movable along
a path parallel to the pipe exit path so that the pipe can be cut
even while pipe continues to be produced. Pipes with a variety of
diameters can be formed by the device 10, and large scale diameter
control is made by adjusting an entry angle of the corrugated metal
strip 24 to the forming head 30. Such angle adjustment can be
achieved by either by rotating the forming head 30 relative to a
stationary corrugation line 20 or by rotating the corrugation line
22, weld table 18 and decoiler unit 12 relative to a stationary
forming head 30. A variety of systems such as that generally
described above have long been used and are available from, for
example, Pacific Roller Die of Hayward, Calif. and IMW Industries
of Chilliwack, British Columbia, Canada.
[0020] The pipe manufacturing device 10 also includes a pipe size
monitoring device 40 along the pipe exit path, in this case shown
downstream of the saw unit 36. However, the pipe size monitoring
device 40 could also be located upstream of the saw unit 36. While
helically corrugated pipe is generally specified, along with other
parameters, by length and diameter, the term "diameter" can be
difficult to apply to the pipe with absolute technical accuracy
because the pipe may actually be slightly out of round. The term
"pipe size" is used herein to broadly refer to any of a perimeter
(inner or outer) dimension of the of the pipe, a diameter dimension
of the pipe, or some other dimension of the pipe that is reflective
of the flow capacity of the pipe, but the term "pipe size"
specifically does not include pipe length. As used herein the term
"diameter" applies even to pipe that may be out of round, in which
case the diameter may be an average radial dimension measured from
a generally centrally located axis of the pipe.
[0021] The pipe size monitoring device 40 can be used to provide
automated pipe size control for pipe 102 as it is produced.
Specifically, the device 10 may include an internal pressure roller
50 located downstream (FIG. 1) and slightly offset laterally of the
lockseam rollers 104 and 106 as shown in FIG. 11. As demonstrated
schematically by FIG. 11, the pressure roller 50 is located for
rolling contact with an inner surface 110 of the pipe 102. In one
example the pressure roller is positioned such that it rolls over
the inner side of one of the box-shaped corrugations 11. The
pressure roller 50 is movable along a vertical path 52 so that the
radially outward pressure applied to the inner surface 110 can be
varied. Due in part to the relative positioning of the pressure
roller 50 between the seaming roll location 51 and the buttress
roll location 53 (both of which are part of the forming head), when
the pressure roller 50 is moved downward (e.g, to position shown by
the dashed line circle) the pressure roller 50 causes the "next
coil" of pipe to be pulled into the lockseam slighly faster, or in
other words with a slightly tighter or smaller curvature (as
reflected in an exaggerated sense by dashed line strip 55), causing
the pipe size to decrease. On the other hand, when the pressure
roller 50 is moved upwards, the next coil of pipe is pulled into
the lockseam slightly slower, or in other words with a slightly
looser or larger curvature, causing the pipe size to increase.
Tightening or decreasing the curvature of the pipe results in an
effective increase in the instantaneous helix angle of the pipe and
loosening or enlarging the curvature of the pipe results in an
effective decrease in the instantaneous helix angle of the
pipe.
[0022] Referring now to FIG. 4, a schematic representation of an
exemplary control system of the pipe manufacturing device 10 is
provided. The pipe size monitoring device 40 provides an output 42
that is indicative of the pipe size as the pipe is being produced.
The output 42 may vary regularly to reflect pipe size changes as
they occur. In one embodiment the output 42 is indicative of pipe
size by way of an analog or digital signal that actually contains
the pipe size information. In another embodiment the output 42 is
indicative of pipe size by reflecting changes from a set point,
those changes being convertible to an actual pipe size by suitable
processing. Either way, a control unit 44 may receive the output 42
and responsively effect operation of an automated drive mechanism
54 that adjusts the position of the pressure roller 50. Thus, it is
seen that the device 10 provides for automated control of pipe size
(e.g., diameter) by providing a feedback arrangement of monitored
pipe size. In one example, the pressure roller 50 and related drive
54 may be configured to provide diameter control within a tolerance
of about one fourth of one percent (0.25%) or better of total pipe
diameter, such as about one sixth of one percent (0.167%) or better
of total pipe diameter or about one eighth of one percent (0.125%)
or better of total pipe diameter. Thus, it is seen that the device
10 provides advantageous pipe size or diameter control during pipe
production.
[0023] In one embodiment the control unit 10 is configured to
provide pipe size control of at least two types. Specifically, in a
first mode the control unit 44 effects operation of the automated
drive 54 so as to maintain a substantially constant pipe size
during pipe production (e.g, by comparing a measured pipe size to a
desired pipe diameter stored in memory of the control unit and
effecting operation of the drive 54 when the measured pipe size
moves outside of a certain range about the desired pipe size, or by
comparing a monitored pipe size variation to a permissible
variation stored in memory and effecting operation of the drive 54
when the monitored pipe size variation exceeds the permissible
variation). In a second mode the control unit 44 effects operation
of the automated drive 54 so as to intentionally vary pipe size
during pipe production (e.g., by comparing the measured pipe size
to a desired diameter as indicated by a desired pipe diameter
profile stored in memory, or by comparing monitored pipe size
variation to a desired variation profiled stored in memory).
Selection of either the first mode or the second mode may be made
via a user interface associated with the control unit 44. In one
embodiment the user interface may take the form of a touch screen
display 46 that displays visual interface keys that an operator can
touch and trigger. However, the user interface could also take
other forms, such as a standard display in combination with a
keypad. In either case, during pipe production the display may 46
provide a continuously updated visual display of measured pipe size
or diameter and/or of variance of pipe size or effective diameter
from a desired pipe size.
[0024] In one example of the above-mentioned second mode, pipe
production is controlled so that a resulting pipe has one end with
a larger diameter than its opposite end. Referring to FIG. 12 where
the profile of such a pipe is shown schematically, a helix angle
.alpha.1 toward larger diameter end 300 is larger than a helix
angle .alpha.2 toward smaller diameter end 302, where the helix
angle is taken at instantaneous locations along the lockseam and is
reference from a central pipe axis 304. It may be difficult to
observe the helix angle difference between opposite pipe ends where
the pipe size is large and the diameter difference between the two
ends of the pipe is only a couple of inches or less.
[0025] The pipe, with ends of different diameters, can then be
worked further to produce a pipe configuration with advantageous
bell and spigot connecting ends. Specifically, the larger diameter
end of the pipe may be worked so as to produce a substantially
corrugation free bell end 120 and the downstream end is worked to
produce a spigot end 122, as shown in FIG. 5 where the bell end 120
and spigot end 122 are shown facing each other for ease of relative
discussion. The bell end 120 includes an outwardly flared entry lip
124 at the end edge of generally cylindrical portion 126. At the
opposite end edge of generally cylindrical portion 126 one or more
annular corrugations 128 are also formed. The spigot end 122 is
formed with one or more annular corrugations so as to provide an
annular gasket seat 130. Notably the very edge of the spigot end
122 flares outwardly. The inner diameter D1 of the bell end 120 is
slightly larger than the outer diameter D2 of the spigot end 122,
enabling the spigot end 122 of one pipe to be readily inserted into
the bell end 120 of another pipe as reflected in FIG. 6. In one
example, the inside diameter D1 of the bell end is at least about
1/3'' greater than the outside diameter D2 of the spigot end 122.
In another example, D1 is at least about 1/2'' greater than D2.
Variations are possible. Also shown is a gasket 132 positioned in
gasket seat 130 so as to seal with the inside surface of bell end
portion 126. The internal portion of annular corrugation 128
provided adjacent the cylindrical portion 126 of bell end 120
serves as an abutment or stop that contacts the outwardly flared
spigot end 122 so that entry of the spigot end into the bell end
120 is limited.
[0026] In one example, an axial length of cylindrical portion 126
is at least about four inches, while in another example an axial
length of portion 126 is at least about six inches. Variations are
possible.
[0027] The working of the end of the pipe to form the spigot end
may be achieved using a suitably formed recorrugator, which is a
device known in the art. Likewise, the working of the end of the
pipe to form the bell end may start by using a recorrugator to form
annular corrugations at the pipe end. The resulting annular
corrugations at the very end of the pipe are then eliminated to
form cylindrical portion 126 by a similar rerolling process.
Alternatively, one or more annular corrugations may be formed in
position slightly spaced apart from the end of the pipe and the
remaining helical corrugations at the end of the pipe may be
eliminated by rerolling to form cylindrical portion 126.
[0028] The device 10 can be used in a process to form multiple
helically corrugated metal pipe segments of similar length that are
readily connectable end to end. Specifically, the method involves:
(a) drawing a metal sheet off of a coil; (b) corrugating the metal
sheet to produce a corrugated metal strip; spiraling the corrugated
metal strip and locking adjacent edges of the spiraled corrugated
metal strip in a crimped manner to produce a helical lockseam; (d)
automatically monitoring pipe size of pipe being produced; (e)
based upon the pipe size monitoring, automatically varying helix
angle of the pipe as it is produced in a manner to intentionally
vary pipe diameter; (f) producing multiple pipe segments by cutting
the helically corrugated metal pipe each time a specified length of
pipe is produced; (g) coordinating the pipe diameter variations of
step (e) with the cutting operations of step (f) such that pipe
segments are produced in the following sequence in a repeating
manner: (1) producing a pipe segment having a downstream end and an
upstream end, a diameter of the upstream end larger than a diameter
of the downstream end, then (2) producing a pipe segment having a
downstream end and an upstream end, a diameter of the upstream end
smaller than a diameter of the downstream end. As a general rule
the diameter of the upstream end of each pipe segment of (g)(1)
will be substantially the same as the diameter of the downstream
end of each pipe segment of (g)(2). For each pipe segment of
(g)(1), the upstream end is rerolled or otherwise worked to produce
a substantially corrugation free bell end, and the downstream end
is rerolled or otherwise worked to produce a spigot end with at
least one annular corrugation. For each pipe segment of (g)(2), the
downstream end is rerolled or otherwise worked to produce a
substantially corrugation free bell end, and the upstream end is
rerolled or otherwise worked to produce a spigot end with at least
one annular corrugation.
[0029] The diameter control from end to end of each pipe segment
may be in accordance with a diameter profile stored in memory of
the control unit. Two exemplary diameter profiles are shown in FIG.
7. In profile 150 the pipe diameter is controlled in a
substantially linear manner between diameters D.sub.A and D.sub.B,
with the pipe being cut at points 152 along the profile. In profile
154 the pipe diameter is controlled so that the diameter is
temporarily held stable, at either diameter D.sub.C or D.sub.D,
before and after each of the cut points 152. Other profiles could
also be developed and used without departing from the scope of this
application.
[0030] Referring now to FIGS. 8 and 9, an exemplary pressure roller
assembly and associated automated drive 54 are shown. Pressure
roller 50 is rotatably held between end brackets 160 and 162 that
extend from a support assembly 164. Support assembly 164 includes
at least two members threadedly engaging each other, where one of
the members is rotatable but has a fixed position along vertical
axis 166 and the other member is non-rotating but is movable along
axis 166. A servomotor 168 is provided to effect rotation of the
rotatable member via a chain and sprocket arrangement or a belt and
pulley arrangement 170. The smaller pulley/sprocket 172 transfers
the rotation to a larger pulley/sprocket 174 to effect rotation of
the rotatable member of support assembly 164. The size and pitch of
the threads of the support assembly members, the relative size of
the pulleys/sprockets 172 and 174 and the precision of the
servomotor 168 can be selected to provide a desired level of
controllability and tolerance for position of the pressure roller
50. The entire pressure roller assembly can be supported off of the
end of the pipe forming head 30 (FIG. 1) so as to be located
internal of the pipe as it is produced.
[0031] Referring now to FIG. 10, an exemplary pipe size monitoring
device 40 is shown and includes steel frame with a base 180 and
upright side supports 182 and 184. Atop support 182 is a ring
member 185 and atop support 184 is a rotatable pulley 186 supported
on axis 190. A tension line 192 (such as a wire, band or rope) has
one end fixed to the ring 185 and loops about the pipe that moves
along the pipe exit path. The tension wire 192 extends to pulley
186 and is fixed for rotation with the pulley 186 by a wire locking
screw 194. A tensioning arm 196 is pivotably connected with the
pulley 186 at axis 198 and is also pivotably connected at a
non-moving location 200 along an upright guide bar 202. A linear
transducer 204 includes one end 206 pivotably connected with the
tensioning arm 196 and its opposite end 208 pivotably connected to
a horizontal support 210. A spring member 212 extends between the
tensioning arm 196 and the horizontal support 210 to bias the
pulley 186 in the counterclockwise direction reflected by arrow
214. A wire source 215, such as a wire spool, is also shown. During
pipe manufacture, increases in the diameter of the pipe are
translated into rotation of the pulley 186 in the clockwise
direction of the pulley 186 as reflected by arrow 216, resulting in
an extension of the linear transducer 204. Conversely, decreases in
the diameter of the pipe are translated into rotation of the pulley
186 in the counterclockwise direction of the pulley 186 as
reflected by arrow 214, resulting in a retraction or shortening of
the linear transducer 204. The linear transducer 204 outputs an
electrical signal that varies with its length. Thus, pipe diameter
variations are reflected by signal changes from the transducer 204,
that can be provided to the above-mentioned control unit 44 (FIG.
4). When it is desired to change from measuring a relatively small
diameter pipe to a relatively large diameter pipe, the wire locking
screw 194 is released to allow sufficient wire or other line to
feed past the pulley 186 for extending about the larger pipe
diameter, and the wire locking screw 194 is again rotated to lock
the wire in place for movement with the pulley 186. Other types of
pipe size monitoring devices could also be used. As used herein
"diameter variations" or "pipe size variations" can be reflected in
a signal that contains an absolute diameter or pipe size
measurement or in a signal that simply departs from a reference
level.
[0032] It is recognized that the position of the pressure roller 50
could also be controlled by operator (e.g., by pushing an up or
down button or by rotating a knob) in response to an indication on
the operator display indicating that pipe diameter is moving or has
moved out of tolerance.
[0033] Referring now to FIG. 13A, one end of a helically corrugated
pipe 400 is shown with a bell end fitting 402 attached thereto. The
end of the pipe 400 is rerolled to eliminate the helical
corrugations but to leave at least one annular gasket seat 404 into
which an annular gasket 406 is placed. The annular gasket 404 might
alternatively be located in the annular corrugation 405 located
closer to the end of the pipe. One end 408 of the bell fitting 402
is configured to slide onto the end of the pipe 400 and to engage
the gasket 406. In the illustrated embodiment fitting end 408
include an outwardly turned lip or flange. The bell fitting 402 is
held on the end of the pipe by a shrink wrap material, the position
of which prior to heat shrinking is shown by solid line 410 and the
position of which after heat shrinking is shown by dashed line 412.
This pipe assembly can be produced in the plant so as to avoid the
need to deal with heating the shrink wrap in the field.
Specifically, the helically corrugated pipe 400 is produced and it
end is rerolled to form the annular gasket seat 404. The annular
gasket 406 is then positioned in the seat. The bell fitting 402 is
typically manufactured with a diameter to assure it can readily
slide onto the end of the pipe 400, but not so large as to have
excessive play relative to the end of the pipe. Once the bell
fitting is slid onto the end of the pipe into the desired position
relative to the gasket 406, the shrink wrap is wrapped around the
pipe as generally shown at 410. Next, the pipe assembly can be
passed by a suitable hot air heating system to cause the shrink
wrap to shrink, thereby securely holding the bell fitting on the
end of the pipe and assuring a good seal. In some embodiments is
may be possible to eliminate the gasket 406 and to rely upon shrink
wrap material alone to form a suitable seal, particularly where the
shrink wrap material is positioned so as to shrink tightly over at
least one annular corrugation crest or other annular formed ring on
each of the pipe end and the bell fitting end.
[0034] The opposite end of the pipe 400 may be configured to be a
spigot end as generally shown in FIG. 13B, with the end rerolled to
provide an annular gasket seat 420. In the field, as pipes are
being connected end to end, a gasket 422 is placed in the gasket
seat 420 of the spigot end of one pipe and the spigot end is then
pushed into the bell end (formed by the bell fitting) of the other
pipe. The gasket 420 forms a suitable seal between the spigot end
and bell end. The bell fitting may include an inwardly extending
lip or corrugation 424 against which the end face 426 of the spigot
end of a pipe will abut, providing a simple manner of assuring that
spigot ends are inserted into bell ends properly.
[0035] It is to be clearly understood that the above description is
intended by way of illustration and example only and is not
intended to be taken by way of limitation, and that changes and
modifications are possible. Accordingly, other embodiments are
contemplated.
* * * * *