Mold useful in sealing leaks in pipes

The present invention is directed to an article and processes for repairing fluid (e.g., liquid and gas) leaks in pipes, including, for example, bell and spigot joints. The device and process of the invention incorporates an elastomeric sleeve that extends around the pipe and longitudinally to either side of the leak. The sleeve contains a resin injection port with means to prevent escape of resin at a pressure above a predetermined pressure, and a fluid venting port with pressure-relief means to permit the escape of fluid at a predetermined pressure above the pressure in the pipe to be repaired.

TECHNICAL FIELD 
The present invention is directed to articles and processes useful in 
repairing fluid (i.e., liquid and gas) leaks in pipes. As it is used 
throughout the specification, the term "pipes" includes lengths of pipe, 
pipe joints, valves, fittings, etc. More particularly, the invention is 
directed to a flexible mold that permits the repair of said leaks rapidly 
and economically without requiring that the flow of fluid in the pipe be 
stopped during repair. 
BACKGROUND ART 
Various devices for repairing fluid leaks, particularly natural gas leaks, 
in various portions of pipes are known. U.S. Pat. No. 3,368,005 describes 
a device useful for repairing leaks in bell and spigot pipe joints. The 
device is wrapped around the joint and a sealant is injected into the 
cavity between the joint and the device. Gas in the cavity is said to be 
able to escape through a flap located where the two ends of the device 
overlap. The flap, however, prevents escape of sealant. 
In order to determine when the cavity is full of sealant, some technique 
must be employed to monitor the pressure therein. Thus, for example, a 
pressure gauge may be utilized. Alternatively, the difficulty in pumping 
additional sealant into the cavity may be observed. Neither of these 
techniques is entirely satisfactory as they may give false indications of 
the amount of resin in the cavity. 
Another such device is disclosed in U.S. Pat. No. 4,053,176. This device 
employs an inlet tube, a baffle or dam by the inlet tube, and a vent. The 
inlet tube is biased so that incoming sealant is steered in a desired 
direction. The baffle is placed in the direction of sealant flow to 
distribute the sealant across the width of the cavity to be filled. The 
inlet tube and the vent are located such that when the device is placed 
around the pipe joint, the inlet tube is located at or near the bottom of 
the joint and the vent is located at or near the top of the joint. 
Locating the inlet in this manner is not satisfactory as it is difficult to 
reach and inject sealant therein. Moreover, no means is provided to 
prevent escape of unhardened sealant from the inlet. Consequently, it is 
necessary to insert some type of plug in it in order to prevent loss of 
sealant. This is cumbersome to do. Still further, the vent is open to the 
atmosphere and has no means to permit escape of sealant therefrom above a 
predetermined pressure. Conversely, it has no means to prevent escape 
below that predetermined pressure. 
DISCLOSURE OF THE INVENTION 
The present invention overcomes these disadvantages. It provides a mold 
useful in sealing fluid leaks in pipes. The mold comprises: 
a sleeve of an elastomeric material dimensioned to fit around a pipe and 
extend longitudinally to both sides of a leak, said sleeve having a resin 
injection port and a fluid venting port located such that, when said mold 
is extended around said pipe and longitudinally to both sides of said 
leak, said fluid venting port is at the top of said pipe, 
means for securing said mold to itself after being placed around said pipe, 
pressure-relief means on said fluid venting port to permit escape of fluid 
at a predetermined pressure above the pressure in said pipe, 
sealing means on said injection port to prevent escape of resin at a 
pressure above said predetermined pressure, 
said mold being at least in part expandable under a pressure less than said 
predetermined pressure. 
For purposes of convenience this disclosure, including the accompanying 
drawings, makes frequent reference to leaks at bell and spigot pipe 
joints. However, as noted above, the mold of the invention may be used to 
repair fluid leaks in other types of pipes.

DETAILED DESCRIPTION 
The mold of the present invention is comprised of an elastomeric material, 
preferably reinforced with fabric. A number of elastomers may be utilized 
in the mold. They include styrene/butadiene rubber, 
ethylene/propylene/diamine monomer, cast urethane, neoprene, etc. Standard 
processing techniques, e.g., rubber molding, may be utilized to 
manufacture the mold. 
Although the mold is primarily intended to be utilized in connection with 
pipes of generally circular cross section, it may also be used with pipes 
of other cross section. Moreover, the mold is preferably split, see for 
example FIG. 1, and may be designed to fit around any size pipe. 
The resin injection port, with its associated sealing means, and the fluid 
venting port, with its associated pressure-relief means, are significant 
aspects of the present invention. The injection port and sealing means 
permit injection of resin into the mold but prevent escape of the resin 
from the mold before it has hardened. The venting port, on the other hand, 
does not permit the escape of material until a predetermined pressure has 
been obtained. The details of these elements of the invention will be 
discussed more fully hereinafter with reference to the drawings. 
The mold of the present invention may be readily employed to repair fluid 
leaks (such as gas leaks) in pipes. Thus, a pipe to be repaired is located 
and any earth or other material therearound is removed so that all sides 
of the pipe may be reached. The pipe is preferably then cleaned by, for 
example, sand blasting, grit blasting, wheat blasting, and refractory 
blasting. Alternatively, the pipe may be cleaned by wire brushing, or 
scraping. 
The mold is then placed around the pipe so that it circumscribes the pipe 
and so that the fluid venting port is at as high a point as possible on 
the pipe. The mold is then attached to itself and secured to the pipe to 
be repaired. 
After being secured to the pipe, resin is injected into the annulus between 
the mold and the pipe. As the resin fills the annulus, the pressure 
therein builds until it exceeds the line pressure of the fluid in the pipe 
stopping the leak. As additional resin is injected into the annulus, the 
pressure therein increases until it exceeds the predetermined pressure of 
the pressure relief means, opening said means and permitting any fluid 
(e.g., gas) in the annulus to escape. When the annulus is substantially 
filled with resin, a small amount of resin will escape from the fluid 
venting port through the pressure-relief means. At this point injection of 
resin is discontinued. Resin will continue to escape from the fluid 
venting port until the pressure in the annulus is equal to or less than 
the pressure at which pressure-relief means opens. 
Once the annulus is substantially filled with resin, the resin is allowed 
to harden and form a rigid seal around the pipe. 
The resin utilized to repair the leak may be selected from a number of 
commercially available materials. An example of such a resin is 
Scotchcast.RTM. 2130, available from the 3M Company. 
Refering to the drawings, FIGS. 1-4, show a mold 10 that represents a 
preferred embodiment of the invention that is well suited for repairing 
fluid leaks in bell and spigot pipe joints. Mold 10 comprises a sleeve of 
elastomeric material having a bell-enclosing portion 11, a 
spigot-enclosing portion 12, a connecting portion 13 joining 
bell-enclosing portion 11 and spigot-enclosing portion 12, a securing 
means 14 for fastening mold 10 to itself after it has been placed around 
the joint, a fluid venting port 15, and a resin injection port 16. Also 
shown is an opening 14a through mold 10 for cooperating with securing 
means 14. 
As can be seen, particularly with reference to FIG. 4, preferred mold 10 
has a unitary, stepped construction. In this construction bell-enclosing 
portion 11 and spigot-enclosing portion 12 project in opposite directions 
from the horizontal plane of connecting portion 13. This gives the cross 
section of mold 10 a generally "S" shape that facilitates its assembly 
around a bell and spigot pipe joint. 
FIGS. 4 and 5 show the details of a preferred fluid venting port 15 of the 
invention. In this embodiment, fluid venting port 15 comprises a shoulder 
17 having a generally dome shape, and a head 18. Shoulder 17 projects 
upwardly from the mold and defines a generally dome shaped cavity 17a. 
Head 18 has a narrow opening 19 that extends from cavity 17a substantially 
all of the way through head 18. Slit 20 connects opening 19 to the outside 
of head 18. Head 18 preferably has a thin rectangular box-like shape whose 
height is greater than its width which in turn is greater than its 
thickness. 
Slit 20 preferably is through the narrowest dimension of head 18, that it 
is at right angles to the width of the head. Slit 20, in conjunction with 
solid portions 18a and 18b of head 18, act as the pressure relief means of 
the invention. Normally, slit 20 is closed and prevents escape of fluid. 
However, when the pressure in the cavity between the mold and the pipe 
exceeds the predetermined pressure, typically one slightly above that of 
the fluid in the pipe, slit 20 opens and permits escape of fluid. The mass 
or the flexibility of the material making up halves 18a and 18b can be 
varied so as to control the pressure at which slit 29 will open. 
The pressure relief means may also be provided in other ways. Thus, for 
example, a spring mechanism designed to be forced open above the 
predetermined pressure, may be attached to venting part 15, typically 
along its width. An example of a useful spring mechanism is a spring 
clamp. 
FIGS. 6 and 7 show the details of the resin injection port 16. Port 16 
comprises a upwardly projecting hollow cylinder having a nozzle-receiving 
cavity 21. Nozzle-receiving cavity 21 terminates in an annular ridge 22. 
Connecting with nozzle-receiving cavity 21 is an intermediate portion 23 
which defines a rounded cavity 23a. Cavity 23a communicates with cavity 
21. A generally rectangular terminal portion 24 is attached to 
intermediate portion 23. Terminal portion 24 has a slot 25 that extends 
from rounded cavity 23a substantially all of the way through terminal 
portion 25. Terminal slit 26 connects slot 25 to the inside of resin 
injection port 16. Preferably slit 26 goes through terminal portion 25 
along its width. 
Slit 26 and intermediate portion 23 together comprise the preferred sealing 
means of injection port 16. While resin is injected into the annulus 
between the mold and the pipe, slit 26 is open. Once injection is 
discontinued the pressure in the annulus pushes against intermediate 
portion 23 causing it to flex inwardly and close slit 26. The slit remains 
closed until the pressure in the annulus is exceeded by the injection of 
additional resin. 
FIG. 8 shows one means for attaching the mold of the invention to itself 
after the mold has been placed around a leaking pipe. The preferred 
fastening means comprises a first rigid plate 27 secured to a bottom of 
one end of the mold, a second rigid plate 28 which is placed over the top 
of the opposite end of the mold, securing means 14, here a threaded post, 
and a nut (not shown). The post passes through plate 27, both ends of the 
mold and plate 28. Openings 30 are provided through plates 27 and 28 and 
both ends of the mold to permit passage of securing means 14. A layer of a 
mastic sealant 29 is preferably placed between the overlapping ends of the 
mold. 
When the mold employed is that of FIG. 1, the mastic 29 and plates 27 and 
28 need extend only across portion 13 of the mold. 
FIG. 9 shows an alternative means of securing the mold to itself. In this 
embodiment a strip of a fastening means 31 is placed on the top of one end 
of the mold and one or more cooperating strips of a fastening means 32 are 
attached to the bottom of the other end of the mold. When strips 31 and 32 
are mated together, they fasten the mold to itself. Providing more than 
one strip 32 enables a repairman to adjust the mold to accomodate the pipe 
joint if necessary. Examples of useful fastening means for this embodiment 
include strips of pressure sensitive adhesive tape, and strips of 
cooperating mechanical fasteners such as HOOK 'N LOOP.RTM. fasteners 
available from 3M Company, or Velcro.RTM. fasteners available from the 
Velcro Corporation. 
FIG. 3 illustrates the mold of FIG. 1 being used to repair a leak in a bell 
and spigot pipe joint. The joint comprises bell 33, spigot 34, and a head 
seal comprising lead 37 and jute 38. As can be seen, the mold has been 
placed around the pipe so that bell-enclosing portion 11 circumscribes 
bell 33, and spigot-enclosing portion 12 circumscribes spigot 34 and fluid 
venting port 15 is at as high a point as possible around the joint. Mold 
10 is then attached to itself as has been described with reference to FIG. 
1. Mold 10 is then secured to bell and spigot portions 33 and 34 of the 
joint by straps 35 and nuts 36. Ring clamps and nuts are shown in FIG. 3 
for this purpose. Other techniques, such as taping or tying, may be 
employed to fasten the mold to the bell and spigot portions of the joint. 
The preferred stepped construction of the mold facilitates its application 
to a bell and spigot pipe joint. Thus, the bell-enclosing and 
spigot-enclosing portions are angled away from the connecting portion so 
that the mold can be applied without having to bend or excessively stretch 
the mold.