Abstract:
An apparatus for rehabilitating an underground water conduit having at least one service entrance including a plug having a light emitter which is responsive to the presence of an electromagnetic field, wherein the at least one service entrance is plugged with the plug and a semi-transparent membrane lining the internal surface of the underground water conduit thereby covering the plug. A drilling head is disposed on a body moveable within the underground water conduit, the drill head having a drill bit and a coil inductor concentric with the drill bit. The coil inductor is adapted to generate an electromagnetic field near the drilling head, wherein the light emitter of the plug is adapted to be turned on by the electromagnetic field emitted by the coil inductor to allow visual alignment of the drill bit with the light emitted by the light emitter through the semi-transparent membrane. The plug is drilled with the drill bit through the semi-transparent membrane in order to reopen the at least one service entrance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of, and claims the benefit under 35 U.S.C. §120 of the earlier filing date of, U.S. patent application Ser. No. 13/623,332, filed on Sep. 20, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a method for rehabilitating an underground water conduit and apparatus for detecting and drilling service entrances in an underground water conduit that have been previously plugged and covered by an internal lining during the rehabilitation process of the underground conduit. 
     BACKGROUND 
     Underground water main conduits and/or sewage conduits that have been installed decades ago have gradually deteriorated to the point where pressurized treated water escapes through cracks and holes at rates that can reach 50%. Similarly. Sewage conduit may have become so deteriorated that a substantial amount of sewage water seeps into the environment instead of being delivered to treatment facilities before re-entering the environment. 
     For many years now, technologies have been developed and used to rehabilitate damaged water and sewage conduits. The various technologies basically consist of re-lining the inside walls of existing underground conduits to rehabilitate the underground conduits. 
     U.S. Pat. No. 5,497,807 describes a method of rehabilitating damaged conduits which consists of inserting a replacement pipe into the existing conduit and filling the gap between the new and old pipe with a filling agent. However, this technology is limited to segments of conduit that do not have side pipes or branch lines connected thereto since those would be blocked permanently. If used in conduits with multiple service entrances or branch lines, each service entrance and branch line would have to be individually reconnected to the main conduit which would require digging the ground up to drill out the rehabilitated conduit and reconnecting each branch line which is expensive and time consuming. 
     U.S. Pat. No. 4,951,758 describes a method of rehabilitating damaged conduits which consists of initially plugging the service entrances of the existing conduit with a water plug carrying a position marker oscillating with a predetermined resonance frequency with a plug setting robot controlled by a technician looking through a video camera connected to the plug setting robot and thereafter lining the existing conduit internally with a continuous strip of synthetic resin wound spirally and filling the gap between the new and old pipelines with a filling agent. Once the re-lining of the existing conduit is done, the water plug can be located with a detection and drilling robot using a loop antenna connected to signal processing circuits which recognise the frequency of the position marker and relay the intensity of the signal to the operator through a graphic display allowing the operator to zero in on the center of the water plug by moving the robot past the water plug until the signal diminishes in the horizontal direction and repeating the process in the radial direction. Once the center of the water plug is located, the water plug is drilled out using a drill mounted on the robot which is operated by the technician. Problems may arise when there are multiple water plugs in the same area giving rise to multiple signals. To alleviate this problem, water plugs with position marker having different resonance frequencies are used when multiple service entrances and branch lines in close proximity to each other need to be plugged. 
     The method described in U.S. Pat. No. 4,951,758 works reasonably well but the detection process requiring multiple passes over the position marker of the water plugs in order to zero in on the center of the water plugs is somewhat tedious and time consuming. As well, the use of water plugs with position marker having different resonance frequencies requires a selection of water plugs to be carried inside the conduit by the robot during the plug setting operation to prevent having to return above ground for water plugs with different resonance frequencies. 
     Therefore, there is a need for a method and apparatus for detecting and drilling plugged service entrances in a conduit after rehabilitation of the conduit which would be less time consuming and eliminate some of the drawbacks of prior art methods. 
     SUMMARY 
     Example embodiments of the present method and apparatus for rehabilitating a water or sewer conduit ameliorate at least some of the inconveniences present in the prior art. 
     Example embodiments of the present method and apparatus for detecting and drilling service entrances in a conduit after rehabilitation of the conduit increase the speed of the operation. 
     In one aspect, the invention provides a method for rehabilitating an underground water conduit having at least one service entrance, the method comprising the steps of: plugging the at least one service entrance with a plug having a light emitter which is responsive to the presence of an electromagnetic field; lining the internal surface of the underground water conduit with a semi-transparent membrane thereby covering the plug; with a drilling head having a drill bit and a coil inductor concentric with the drill bit, the coil inductor being adapted to generate an electromagnetic field near the drilling head, generating an electromagnetic field while moving the drilling head inside the underground water conduit until the light emitter of the plug is turned on by the electromagnetic field; visually aligning the drill bit with the light emitted by the light emitter through the semi-transparent membrane; and with the drill bit, drilling the plug in order to reopen the at least one service entrance. 
     In another aspect, the invention further comprises a camera connected to a television monitor aboveground which is positioned in front of the drilling head for visually detecting the light emitted by the light emitter through the semi-transparent membrane and for aligning the drill bit with the light emitted by the light emitter. 
     In another aspect, the invention provides a service entrance plug to be used in the method for rehabilitating an underground water conduit comprising at least one an antenna coil connected to the light emitter, the antenna coil being adapted to generate an electrical current when subjected to an electromagnetic field that will turn on the light emitter. 
     Embodiments of the present invention each have at least one of the above-mentioned aspects, but do not necessarily have all of them. 
     Additional and/or alternative features, aspects, and advantages of embodiments of the present invention will become apparent from the following description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where: 
         FIG. 1  is a schematic cross-sectional view illustrating a deteriorated underground water main conduit having three service entrances; 
         FIG. 2  is a schematic cross-sectional view of the deteriorated underground water main conduit of  FIG. 1  and a plug dispensing and setting robot and camera assembly therein; 
         FIG. 3  is a schematic side elevational view of a service entrance plug having a light emitting device in accordance with one embodiment; 
         FIG. 3 a    is a schematic bottom plan view of the service entrance plug having a light emitting device of  FIG. 3 ; 
         FIG. 4  is a schematic side elevational view of a service entrance plug having a light emitting device in accordance with a second embodiment; 
         FIG. 4 a    is a schematic side exploded view of the service entrance plug having a light emitting device of  FIG. 4   a;    
         FIG. 5  schematic cross-sectional view of the deteriorated underground water main conduit of  FIG. 1  after a rehabilitation lining has been installed therein; 
         FIG. 6  is a schematic cross-sectional view of the rehabilitated underground water main conduit of  FIG. 5  and a plug detection and drilling robot and camera assembly therein; 
         FIG. 7  is a schematic side elevational view of a drilling head of the plug detection and drilling apparatus in accordance with one embodiment; and 
         FIG. 8  is a schematic top plan view of the drilling head of  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  depicts a segment of an underground water main conduit  10  which is in an advance state of deterioration. Water main conduit  10  includes multiple holes, cracks or punctures  12  caused by excessive rust, cracks or soil movements, for example, that allow pressurized water to escape from the water main conduit  10  into the soil, generating drops in pressure and considerable waste of treated water. Water main conduit  10  includes three service entrances  14 ,  16  and  18  linking water main conduit  10  to households or businesses supplying fresh water to the occupants. 
     When a segment of an underground water main conduit is in a state of deterioration as water main conduit  10  is depicted in  FIG. 1 , two options are available: Replacing the entire segment which entails the costly and time consuming process of digging the ground up to remove the segment of water main conduit  10  and install a new segment, or re-lining the inside walls of the underground water main conduit  10  to cover and close the multiple holes, cracks or punctures  12  and restore the inside walls of the water main conduit  10  which is less expensive and time consuming. 
     The process of re-lining a segment of underground water main conduit  10  requires that the service entrances  14 ,  16  and  18  be plugged prior to re-lining the water main conduit  10  to prevent any resin from seeping into the service entrances and clogging them. As illustrated in  FIG. 2 , a plug setting robot  20  connected to a closed circuit camera  22  through a tension cable  24  at a predetermined distance are introduced together into the water main conduit  10 . The plug setting robot  20  and the camera  22  are respectively connected to tension cables  27  and  29  which are connected to a pair of winches (not shown) located above ground and operated by a technician. The assembly of the plug setting robot  20  and camera  22  is moved back and forth inside the water main conduit  10  by actuated one of the winches which pulls on one of the tension cables  27  and  29  while the other winch offers little resistance. The assembly of the plug setting robot  20  and camera  22  is remotely operated by the technician looking at a television monitor (not shown) relaying live images captured by the camera  22 . 
     The plug setting robot  20  comprises a main body  25  housing a power unit and actuator for controlling a dispensing head  30  positioned at the front of the plug setting robot  20 . The dispensing head  30  which is rotatable about an axis extending in a horizontal direction and movable back and forth in the horizontal direction for precise alignment with one of the service entrances  14 ,  16  or  18 . The dispensing head  30  is also movable in the radial direction to press a plug  32  into the service entrances. On top of the camera  22  is a magazine  28  housing a series of plugs  32  aligned so that they may be retrieved one by one by the dispensing head  30 . The plug setting robot  20  and the camera  22  are mounted on low friction pads  26  such that they can slide onto the bottom surface of the inside wall of the water main conduit  10 . 
     In operation, the technician, looking at a television monitor, moves the plug setting robot  20  to align the dispensing head  30  with one of the service entrances  14 ,  16  or  18 . The dispensing head  30  is then moved forward to retrieve a plug  32  or  33  from the magazine  28  located on top of the camera  22  and returned to its position in line with the service entrance  16  as illustrated  FIG. 2 . Minute adjustments are made in the radial direction by the technician viewing the alignment through his monitor and then the plug  32  or  33  is inserted and pressed into the service entrance  14  by the dispensing head  30  moving towards the service entrance  16 . The dispensing head  30  is then retrieved and the technician moves the assembly of the plug setting robot  20  and camera  22  by actuating the winches to align the dispensing head  30  with another service entrance and the cycle is repeated until all the service entrances  14 ,  16  or  18  are plugged. 
     As illustrated in  FIG. 3 , a first embodiment of the plug  32  includes of a conical hollowed body  34  made of a soft plastic surrounded by a series of flexible winglets  36  adapted to bend when plug  32  is inserted into the service entrance in order to efficiently seal the service entrance. The body  34  has first and second ends, wherein the smaller diameter first end is adapted to be inserted into a service entrance and the larger diameter second end is adapted to be visually seen within the underground water conduit. The bottom winglet  38 , disposed on the second end, has a larger diameter than the flexible winglets  36 , is marginally thicker than flexible winglets  36  and is designed to rest on the edge or perimeter of the service entrance. 
     As illustrated in  FIG. 3 a   , the bottom winglet  38  includes an antenna coil  40  connected to a light emitter  42  located exactly in the center of the winglet  38 . The antenna coil  40  is adapted to generate a small electrical current when subjected to an electromagnetic field that will turn on the light emitter  42 . 
     With reference to  FIGS. 4 and 4   a , a second embodiment of a plug is illustrated consisting of a two-piece plug  33  which also includes of a conical hollowed body  34  made of a soft plastic surrounded by a series of flexible winglets  36  adapted to bend when the hollowed body  34  is inserted into the service entrance in order to efficiently seal the service entrance. The body  34  has first and second ends, wherein the smaller diameter first end is adapted to be inserted into a service entrance and the larger diameter second end is adapted to be visually seen within the underground water conduit. The body  34  includes, in its second end, a receptacle winglet  37  having a larger diameter than the flexible winglets  36  designed to rest on the edge or perimeter of the service entrance. The receptacle winglet  37  extends inwardly to define an annular lip  39  adapted to hold a cap  41  which is snapped into the annular lip  39  of the receptacle winglet  37  as shown in the exploded view of  FIG. 4 a    by the dotted arrow. The snap-on cap  41  includes a groove  43  which secures the snap-on cap  41  to the annular lip  39  of the receptacle winglet  37 . The antenna coil  40  and light emitter  42  shown in  FIG. 3 a    are embedded in the snap-on cap  41 . 
     In operation, the installation of the two-piece plug  33  into the service entrances  14 ,  16  and  18  may be a one step process in which the assembled two-piece plug  33  including the cap  41  is inserted and pressed into the service entrances by the plug setting robot  20  as previously described, or a two step process in which the body  34  of the two-piece plug  33  is first inserted and pressed into a service entrance by the plug setting robot  20  and then the plug setting robot  20  retrieves a cap  41  including the light emitter  42  from a second a magazine (not shown) housing a series of caps  41  which it inserts into the internal groove  39  of the receptacle winglet  37  of the body  34  previously inserted and pressed into the service entrance. 
     Once all the service entrances  14 ,  16  and  18  are plugged with the plugs  32  or  33  comprising a light emitter  42 , the segment of underground water main conduit  10  may be re-lined. A tubular membrane  50  comprising of a pair of concentric circular weave polyester fiber hoses impregnated with epoxy resin is introduced inside the water main conduit  10 . The tubular membrane is cooked with hot water under pressure such that the tubular membrane  50  adheres to the inner wall of the water main conduit  10 . In the cooking operation, the resin migrates into the circular weave polyester fibre hoses and renders the tubular membrane  50  semi transparent when the resin has cured. As illustrated in  FIG. 5 , when the tubular membrane  50  has cured and solidified, the multiple holes, cracks or punctures  12  of water main conduit  10  described with reference to  FIG. 1  are completely covered and the water main conduit  10  is watertight. In the process, the service entrances  14 ,  16  and  18  are also completely covered by the tubular membrane  50 . 
     Once the tubular membrane  50  has cured and solidified, the service entrances  14 ,  16  and  18  must be located and the plugs  32  or  33  drilled out in order to re-open the service entrances  14 ,  16  and  18  to supply water to the residences or businesses linked to the water main conduit  10  through the service entrances  14 ,  16  and  18 . 
     To locate the plugs  32  or  33  and drill them out, a drilling robot  60  connected to a closed circuit camera  22  and a generator  61  are introduced together into the tubular membrane  50  of the water main conduit  10  as illustrated in  FIG. 6 . The drilling robot  60 , the camera  22  and the generator  61  are connected together as an assembly through tension cables  24 . The drilling robot  60  and the generator  61  are respectively connected to tension cables  27  and  29  which are connected to a pair of winches (not shown) located above ground and operated by a technician. The assembly of the drilling robot  60 , the camera  22  and the generator  61  is moved back and forth inside the water main conduit  10  by actuated one of the winches which pulls on one of the tension cables  27  and  29  while the other winch offers little resistance. The drilling robot  60  and the generator  61  are mounted on low friction pads  64  such that they can slide on the inside of the tubular membrane  50  within the water main conduit  10 . The assembly is remotely operated by the technician looking at a television monitor (not shown) relaying live images captured by the camera  22 . 
     The drilling robot  60  comprises a main body  62  housing a power unit and actuator for controlling a drilling head  66  positioned at the front of the drilling robot  60 . The drilling head  66  includes a drill bit  68  extending perpendicular to main body  62  and the longitudinal axis of the water main conduit  10 . The drilling head  66  is rotatable about an axis extending in a horizontal direction and also movable back and forth along the same axis such that the technician is able to precisely align the drill bit  68  with service entrances located in any position around the circumference of the water main conduit  10 . 
     With reference to  FIGS. 7 and 8  which are enlarged views of the drilling head  66 , a coil inductor  70  is mounted on the drilling head  66 . The winding of the coil inductor  70  is concentric with the axis of the drill bit  68  and preferably oval shaped as illustrated in  FIG. 8  in order to provide a wider sweep than a regular round shape. Referring back to  FIG. 6 , the generator  61  is electrically connected directly to the coil inductor  70  through an electrical wire  72  to provide the required electrical current to the coil inductor  70 . When an electrical current flows through the coil inductor  70 , the coil inductor  70  generates an electromagnetic field. 
     With reference to  FIG. 6 , in operation, the drilling robot  60  is moved inside the water main conduit  10  by the technician into an area where one of the service entrances  14 ,  16 , or  18  was plugged by a plug  32  or  33 . The technician then activates the coil inductor  70  to generate an electromagnetic field. When the electromagnetic field generated by the coil inductor  70  is in the vicinity of a plug  32  or  33 , the antenna coil  40  of the plug  32  or  33  generates a small electrical current that turn on the light emitter  42 . The semi transparent characteristic of the tubular membrane  50  allows the light emitted by the light emitter  42  to pass through the tubular membrane  50  such that the light can be seen by the technician through the camera  22  positioned directly in front of the drilling head  66 . The light emitted is preferably red and flashing for ease of detection. 
     The technician is able, through the camera  22 , to visually align the end of the drill bit  68  with the flashing red light by moving the drilling robot  60  back and forth, by rotating the drilling head  66 , and moving the drilling head  66  up and down to be as close as possible to the surface of the tubular membrane  50  and to the flashing red light such that the end of the drill bit  68  is precisely aligned with the plug  32  located behind the tubular membrane  50 . Since the light emitter  42  is exactly in the center of the plug  32  or  33  as previously described, the alignment of the end of the drill bit  68  with the flashing red light aligns the drill bit  68  with the center of the plug  32  or  33  and therefore the center of the service entrance  14 . Once the alignment is done, the technician actuates the drill bit  68  and proceeds with drilling out the plug  32  or  33  by moving the drilling head  66  through the tubular membrane  50  and through the plug  32  or  33  located behind the tubular membrane  50  far enough to completely drill out the plug  32  or  33 . The drilling head  66  is then retrieved and the drilling robot  60  is moved into an area where another of the service entrances  14 ,  16 , or  18  was plugged by a plug  32  or  33  and the cycle of detection, alignment and drilling is repeated until all the plugs  32  or  33  have been drilled out and all the service entrances  14 ,  16  and  18  reopened. 
     The combination of the tight emitter  42  positioned at the center of the plug  32  or  33  responsive to the electromagnetic field generated by the coil inductor  70  enables the technician to visually align the drill bit  68  with the center of the plug  32  or  33  as opposed to relying on some other signals which has the beneficial effect of accelerating the drilling process and therefore accelerating the reopening of the water main conduit  10  after rehabilitation. 
     Modifications and improvements to the above-described embodiments may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present invention is therefore intended to be limited solely by the scope of the appended claims.