Fluid loop cooling of lighthead

Abstract

A cooling system for a lighthead. The cooling system uses a liquid coolant, rather than air. An umbilical is mounted on a rotating drum, which is used for storage and deployment of the umbilical. The umbilical includes at least one power and data transmission line, a coolant return line and a coolant supply line. The lighthead has physical features that direct and interrupt the flow of the liquid coolant to provide mixing, so that light emitting diodes used by the lighthead will have waste heat more efficiently transported away. A thin, disc-shaped heat exchanger is mounted on and rotates with the rotating drum. A fan or other cooling system is used to cool the liquid coolant returned from the lighthead, and the resulting liquid coolant is pumped back to the lighthead.

Description

Fluid Loop Cooling of LightheadSUMMARY

[0001] The present invention is directed to a system for cured in place pipe repair. The system comprises a lighthead, an umbilical, and a heat exchanger. The lighthead comprises a plurality of light emitting diodes and includes a cooling chamber. The umbilical is attached to the lighthead and comprises an electronic cable connection, a coolant supply line and a coolant return line. The electronic cable connection is configured to provide power to the plurality of light emitting diodes. The coolant supply line is configured to provide liquid coolant to the cooling chamber, and the coolant return line is configured to receive liquid coolant from the cooling chamber. The heat exchanger is configured to receive liquid coolant from the coolant return line and return liquid coolant to the coolant supply line.

[0002] In another aspect, the invention is drawn to a method for cooling a light array in a lighthead for use in a CIPP curing system. The method comprises deploying the lighthead into a pipe. The lighthead is attached to a rotating drum by an umbilical. The method further comprises illuminating the lighthead using the light array to cure a liner on an inner surface of the pipe, providing a low temperature liquid coolant to the lighthead through the umbilical, and cooling the light array with the low temperature liquid coolant.

[0003] The method further comprises removing a high temperature liquid coolant from the lighthead through the umbilical, placing the high temperature liquid coolant into a heat exchanger located proximate the rotating drum, thereby returning the coolant to its low temperature condition. Thereafter, the low temperature liquid coolant is returned to the lighthead through the umbilical.

[0004] A coolant pump is used to drive fluid through the system in conjunction with the method.BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 is a modified isometric front view of a lighthead.

[0006] Figure 2 is a modified isometric rear view thereof.

[0007] Figure 3 is a side view thereof.

[0008] Figure 4 is a section view thereof.

[0009] Figure 5 is a modified isometric rear view of the novel lighthead partially disassembled.

[0010] Figure 6 is a detail view of Figure 5.

[0011] Figure 7 is a modified isometric front view of the novel lighthead concept partially disassembled.

[0012] Figure 8 is a modified isometric view of the LED array free from the novel lighthead.

[0013] Figure 9 is a schematic diagram of the novel lighthead concept.

[0014] Figure 10 is a schematic diagram of a prior art pneumatic cooled lighthead.

[0015] Figure 11 is an isometric view of an alternative lighthead.

[0016] Figure 12 is an isometric view of the lighthead of Figure 11, partially disassembled.

[0017] Figure 13 is a rear isometric view of the lighthead of Figure 11.

[0018] Figure 14 is a rear view of the lighthead of Figure 11 with section lines shown.

[0019] Figure 15 is section view B-B of Figure 14.

[0020] Figure 16 is section view A-A of Figure 14.

[0021] Figure 17 is section view C-C of Figure 14.

[0022] Figure 18 is an isometric view of a short section of an umbilical line that services the lighthead of Figure 11.

[0023] Figure 19 is a right-front isometric view of a mobile cart with pancake heat exchanger concept.

[0024] Figure 20 is a left -front isometric of a mobile cart with the drum assembly removed for clarity.

[0025] Figure 21 is a right side view of a pancake heat exchanger concept isolated from the mobile cart.

[0026] Figure 22 is a rear view of a pancake heat exchanger concept isolated from the mobile cart.

[0027] Figure 23 is a right side view of the coolant passage of a labyrinth plate of a pancake heat exchanger.

[0028] Figure 24 is an isometric view of a lighthead train for use with the invention.

[0029] Figure 25 is a top view of an individual lighthead within the train of Figure 24.

[0030] Figure 26 is section A-A from Figure 25, showing a sectional view of the lighthead.

[0031] Figure 27 is detail view B taken from Figure 26, showing internal passageways within the lighthead.

[0032] Figure 28 is an isometric view of the lighthead body, with the LED arrays removed.DETAILED DESCRIPTION

[0033] Cured-in-place-pipe (CIPP) makes use of a resin impregnated woven or matted fiber tubular sleeve to provide modest structural support and an unbroken, sealed conduit to remedy leaking and / or structurally compromised buried pipes. These pipes may conduct sanitary or storm water and are often made of segmented, non-continuous lengths of clay, concrete or other materials that have degraded with time.

[0034] A particular range of light waves, such as blue light, may be used to initiate the catalyst mixed into the resin once the resin-soaked sleeve like liner is deployed within the host pipe and expanded. The light sources are less than 100% efficient, producing heat as a byproduct. As the pipe in which the light sources are situated often do not conduct heat away from the sources, the heat must be removed from the light source so as not to damage the light source, often an LED, due to these excessive temperatures.

[0035] The invention disclosed herein removes the byproduct heat by wetting an internal chamber within the lighthead with a liquid cooling fluid to absorb excess heat and carry it through an umbilical hose to a thermal sink at the surface. After this cooling heat iscooled at the sink, the cooled liquid is returned, again through the umbilical in a parallel hose, to the lighthead to repeat the process in a continuous looping manner.

[0036] Current applications to cool lightheads have used compressed air flowing as a cooling medium to remove the byproduct heat. Further, this air is allowed to return to the surface via the uncured portion of the liner, creating a total loss cooling system. Total loss cooling systems are commonly used in heat generating devices. For example, small residential lawnmower engines use ambient air to absorb heat and reject that heat with a fan to a more distant area. These are simple and cost effective, however they may not allow for maximization of the power potential in the device. High performance engines use liquid cooling in a closed loop cooling system. High performance engines produce more power and therefore more waste heat for their physical volume than typical low performance utility engines such as a lawnmower.

[0037] Air is a useful medium for cooling as it is of negligible weight, can be directly expelled, and is free. Because of its low density, however, it is not as effective in transporting heat away from a device as liquid coolant, especially for high output (and therefore high waste heat) devices.

[0038] An example that liquid cooling is more effective for high output devices is the transition away from air-cooled automobile engines such as the VW bug of the 1960’s which produced 37 horsepower (“hp”) per liter of displacement to the current typical four-cylinder 2.0-liter engine which easily produces 100 hp per liter. This modern power density would not be possible with air-cooling as the engine would quickly overheat and fail.

[0039] Lightheads may be regarded as a high-performance device. They must be small so they can not only fit into the interior of a small diameter pipe, but also short so they can negotiate passage through 45- and 90-degree bends. They must maximize the amount of light energy emitted within the modest volume allowed by the constraints of the pipe. These constraints include the flow rate of provided cooling medium, which is limited because of the umbilical bundle by which any coolant (both low temperature and hightemperature return) must be transported. Given the need for a high-performance design, a change from total loss air cooling to closed loop liquid cooling is advantageous.

[0040] The combination of high ambient temperatures and the desire to maximize lighthead travel speeds by maximizing light output requires that a coolant more effective than air be utilized to transfer waste heat from the LEDs through the host pipe to the surface. Applying this revelation creates several hurdles that must first be cleared.

[0041] The first challenge is transferring the heat from the LEDs into the coolant. The lightheads are designed to be small as they must fit inside a lined 4” or even smaller pipe. Lightheads are also short so they can navigate through pipe elbows without becoming hung up. Short and small leave little surface area to transfer the heat. For this reason, the coolant flow path must be optimized using novel concepts to ensure that the LEDs stay at or below an acceptable maximum temperature, thereby prolonging service life. The high heat capacity of liquid coolants, such as an ethylene glycol / water mix, aids with this. A 50% mixture, plus or minus 20%, is one preferable coolant, though others can be used without departing from the spirit of the invention.

[0042] The second challenge is a byproduct of the storage of the umbilical as the umbilical is best coiled into a rotating drum as the lighthead is retrieved from the far end of the host pipe. Storage of the lighthead, umbilical line and electronic control systems that power and regulate the lighthead is done on a piece of mobile equipment with wheels that is maneuvered about the jobsite similar to a 2 wheeled dolly. Said cart also mounts a hollow drum into which the umbilical is coiled like hose onto a hose reel. The drum is mounted rotatably on a bearing supported hub, the hub configured with slip rings to transfer power and control signals from the stationary (non-rotating) electronics mounted on the cart to the constantly rotating coiled umbilical stored inside the drum.

[0043] It is the rotation of the umbilical stored in the drum that creates a challenge for the discharge of the heat that was transferred to the coolant from the LEDs affixed to the lighthead. The umbilical is made up of an outer tube most desirably manufactured from some form of moderately flexible plastic. Within that tube is an electrical conductor wiretasked with providing power to and control of the lighthead as well as supply and return lines for the coolant. Optionally the umbilical tube may contain a fiberglass rod to add stiffness for thrusting the umbilical and lighthead through the host pipe. As noted, the coiled umbilical rotates with the storage drum on the bearing supported hub. Power and electrical control are passed through slip rings within the hub. The heat transported by the coolant lines must be rejected to the atmosphere in order to complete the cooling process cycle.

[0044] The inclusion of the coolant medium in an umbilical which is, itself, stored in and deployed from a rotating drum, makes the conveyance of coolant to and from a heat exchanger difficult. The present invention is a way to make the heat exchange make sense, given space and movement constraints associated with CIPP repair.

[0045] While the improvements in velocity through the uncured liner offered by LEDs has been impressive, the method encounters a challenge when used in high ambient temperatures. This occurs when the cooling medium sourced at the surface and transported through the umbilical line to the lighthead begins the cooling process at an unreasonably high temperature.

[0046] It is normal for a construction crew to work through the afternoon hours with ambient air temperatures above 110F. Ambient air which is subsequently compressed which results in further temperature rise is then passed through the umbilical to the lighthead is intended to cool the LEDs. The LED temperature should not exceed 175F for good service life. This air-cooling process is documented in prior art such as U.S. 9,453,607 Moeskjaer, the contents of which are incorporated herein by reference.

[0047] The heat exchanger is a component that requires meaningful surface area to transfer or dump the heat from the coolant to the outside air. The challenge of transferring the heat is compounded by the fact that modest temperature differential between the lighthead at 175F and ambient air at 110F. Getting a low enough coolant temperature to keep the LEDs at 175F or less means the coolant must enter the lighthead at a temperature around 125F. Cooling a liquid to a temperature close to the sink (ambient air in this case)requires that the liquid spend an extended amount of time in the heat exchanger. That means the heat exchanger needs to be large to provide time and have sufficient surface to bring the coolant within 15F of the ambient sink temperature.

[0048] Having a large heat exchanger mounted in a stationary manner on a cart would be a simple task, however it would also add the engineering design requirement of proving two swiveling flow channels in the hub to move the coolant from the rotating zone of the drum to the stationary zone beyond the drum to the cart frame. This is possible, though undesirable as swivels tend to develop leaks, add rotational friction which impairs the progressive storage of the umbilical in the drum and are often costly.

[0049] A solution is to make the heat exchanger rotate with the drum thereby avoiding the need for liquid conducting swivels. Further the pump that circulates the coolant through the cooling system need also be configured to rotate with the drum and the heat exchanger. A fan, which is needed to achieve good performance from a heat exchanger, is also required. Air need not be neatly contained, meaning the fan can be mounted on the cart frame in a stationary manner and positioned to blow or draw ambient air across the heat exchanger through a duct. This leaves the tasks of configuring the heat exchanger and pump to be mounted in a manner that they rotate about the hub axis along with the umbilical stored in the drum without excessively adding to the size of the mobile cart.

[0050] The primary function of a cart is to mount the drum and allow it to rotate freely during lighthead deployment and retrieval while initiating resin cure. The drum is about 32” in diameter and 10” wide and could be described as a thick disc rotated about its cylindrical axis which is oriented horizontally due to the hub mounting on the cart. The width of the cart is more or less determined by the drum and framework required to support the hub.

[0051] A narrow overall width produces desirable maneuverability and storage characteristics. The design of the heat exchanger and pump mount should not detractsignificantly from those characteristics. An ideal concept that is novel and maintains the disc-like form is what has been dubbed a pancake heat exchanger.

[0052] A thin disc-shaped exchanger with heat transfer fins exposed to an airstream created by a fan is concentrically mounted on the hub axis and stacked beside the drum. A coolant pump is affixed to the heat exchanger to move the coolant through the umbilical to and through the lighthead, return it to the drum, through the heat exchanger for cooling and finally return to the pump inlet port.

[0053] The drum, which is interchangeable with other drums having lightheads and umbilical properties intended for lining specific pipe sizes must be easily removed and substituted. The pancake heat exchanger and pump are items of meaningful cost and need not be replicated with each drum assembly. Therefore, the drum portion of the cooling circuit made up of the coolant supply and return lines in the umbilical along with the lighthead must be easily decoupled / coupled from / to the pancake heat exchanger and pump portion of the cooling circuit. In this way the heat exchanger and pump remain on the mobile cart while the drum and its related components can be swapped out as a kit for job specific needs.

[0054] The pancake shape of the heat exchanger ideally has the fan supplied cooling air initially directed along its central axis whereupon striking fins on the face of the heat exchanger, the air disburses radially along the direction of the fins removing the heat from the fins and transporting it away from the exchanger.

[0055] The coolant passages within the plate-on-plate pancake configuration are voluminous, thereby encouraging lazy flow velocities. Further, the heat exchanger is divided into two sections, the first, shorter area of the exchanger cools the hottest coolant as it arrives from the lighthead. The second, larger section houses the coolant after the first section has dropped the coolant temperature. Note that higher differential temperatures from coolant to sink allow for faster rates of cooling. Thus, the first section of the coolant flow path in the heat exchanger serves the purpose of quickly dissipating heat from the hightemperature coolant while the second section allows the coolant to linger, a requirement to facilitate getting the coolant to approach the sink temperature within 15F.

[0056] Upon wicking, the byproduct waste heat of the LEDs from the cooling chamber of the lighthead, the cooling fluid is returned through a hose in the umbilical bundle to the surface. At the surface, the fluid may pass through a cooler before entering an optional modest size reservoir. The cooler is a tube and fin radiator and may have a fan to pull or direct ambient air through it.

[0057] Alternatively, for extremely high cooling capability, the fluid may pass through a powered refrigeration chiller that will cool the fluid below ambient temperatures with the chiller passing the heat onto the atmosphere.

[0058] The cooler can be regulated by a thermostat if desired. Said thermostat might limit the amount of cooling before a threshold temperature is reached at which time a fan may be started or the chiller engaged. Should the cooling fluid have a viscosity decrease with increased temperature, there will be lower pumping losses through the long lines if the cooling fluid is allowed to come up to operating temperature quickly.

[0059] The cooling fluid should have a high specific heat content per unit weight. Water or water / ethylene glycol mix are examples of high specific heat with the additional benefit of low viscosity for lowered pumping pressures. A third option that has a side benefit is cooling oil intended for submersion cooling of electronic components. Dielectric oil has a high specific heat value and works well with pumps because of its lubricity and corrosion inhibiting. It does however have a higher viscosity than water or water / glycol mix. A side benefit is that the contacts and electrical connections will function normally if they are directly exposed to said oil, thereby adding to the heat removal and providing design options.

[0060] These concepts can be applied to discrete lightheads, or can be used with multiple lightheads in series. These “light trains” maybe carried on wheels and are typically used in larger pipes, such as 24” diameter pipes and larger formats. Eachlighthead in the “train” will be connected in a manner that allows pivoting such that pipe bends can be negotiated.

[0061] With reference now to the figures, a pair of lightheads 10, 200 for use with the drum and heat exchanger of the present invention are shown. The lightheads 10, 200 share features, and when features are the same, the same reference numbers will be used. Where distinctions between lightheads 10, 200 exist, they will be noted. It should be understood that features not common between the different embodiments of lightheads 10, 200 maybe exchanged without departing from the spirit of the invention.

[0062] In addition, a lighthead train 300 is shown with individual lightheads 310 in Figures 24-28. While specific features of a lighthead train 300 maybe different, the guiding principles of the drum and heat exchanger may be similar or identical.

[0063] Figures 1 and 2 show the lighthead 10 with a camera 14 at the forward nose. Likewise, Figures 11 and 12 show a camera disposed on lighthead 200. The lightheads 10, 200 have a nose cap 13 that mounts the camera 14, and a series of LED arrays 11 that are circumferentially mounted beneath a protective glass cover 12. A tailcap 18 provides a seal for the housing body 39 (Figure 4).

[0064] A tailpiece 15 protects the items making up the umbilical conduits 17 where they attach to the tailcap 18. The tailpiece 15 is made up to the assembly by fasteners 22 (Figures 2, 4). Alternatively, the tailpiece 15 may be attached to the assembly through a threaded connection.

[0065] An umbilical subassembly 16 covers and protects the hoses, electrical wire and pushrod that make up the umbilical conduits 17. As discussed, the umbilical conduits 17 convey fluid and power uphole. The umbilical conduits 17 comprise at least an electrical multi conductor electrical cable 24, a coolant hose inlet 23, a coolant hose return 26 and a pushrod 25.

[0066] While the umbilical subassembly 16 has discrete umbilical conduits 17, as disclosed herein, it should be understood that the umbilical itself may be utilized for thesupply or return of coolant, such that the cross-section between the umbilical 16 and each of the conduits 17 maybe itself used as a conduit.

[0067] Figures 3 and 5 are side views of the fully assembled lighthead 10. The lighthead has a groove on nose cap 13. The groove is intended to provide a feature to secure mule tape (or another attachment mechanism) in order to provide towing assist to move the lighthead 10 through longer runs of pipe. The camera is held in place within the nose cap 13 by a camera retainer 36. An O-ring 29 is located at each end of the glass cover 12 to seal the lighthead assembly 10. The nose cap 13 is held in place by threads 37 located on the housing body 39.

[0068] Sensors 202 maybe placed inside the nose cap 13 (FIG. 12) to monitor temperature and other performance characteristics.

[0069] The housing body 39 contains a cylindrical coolant chamber 27. The chamber27 is traversed by a conduit conductor 31. The conduit conductor 31 is sealed at each end. The conduit conductor 31 may be sealed by an O-ring 38 and a press fit joint 33. These seals prevent the multiconductor electrical cable 24, located within the conduit conductor 31, from being wetted by the fluid coolant that is located during use within the cylindrical coolant chamber 27.

[0070] A coaxial cable 32 extends from within the multiconductor electrical cable 24 into the camera 14. LED arrays 11 are made up of individual light emitting diodes 43 mounted to circuit boards 45. The circuit boards 45 are mounted to the outer wall of the housing body 39.

[0071] The tailcap 18 is threaded to the housing 39 at joint 30 and sealed by an O- ring 28. The pushrod 25 utilizes a threaded joint 35 to transmit thrust forces from uphole to move the lighthead 10 through the host pipe 49. A conductor clamp 34 secures the multiconductor cable 24 to the tailcap 18 and therefore the lighthead assembly 10.

[0072] As best shown in Figure 6, coolant supply line 23 and coolant hose return 26 are attached to tailcap 18. The multiconductor cable 24 is shown exiting the tailcap 18 with an angled path, retained by conductor clamp 34 which is secured to tailcap 18, but the angleof exit is demonstrative and not limiting on the invention. The tailcap 18 may also have one or more mount threads 40 to attach to tools, for example, to help to open the lighthead assembly 10.

[0073] In Figure 7, the lighthead 10 is partially disassembled to remove the LED Arrays 11. Mounting flats 41 on the lighthead housing 39 are provided to mount the LED Arrays 11. The mounting flats 41 provide structural security as well as a heat sink to absorb waste heat from the LED arrays 11. A power lead 42 extends from the multiconductor electrical cable 24 to the LED array 11. A matching power lead 42 may follow a similar path on the opposite side of housing 39.

[0074] In Figure 8, the LED array 11 is shown in more detail. The multiple individual light emitting diodes 43 are mounted on a traditional circuit board 45, which is in turn adhered in a thermally conducive manner to the lighthead housing 39. A solder pad 44 is shown for connection of the board 45 to a power lead 42.

[0075] With reference now to Figures 9 and 10, a simplified schematic is shown. Figure 9 is the present invention. Figure 10 represents the prior art method.

[0076] In Figure 9, an existing (host) pipe 49 buried below the surface has a resin impregnated liner 53. Within the liner 53 is the lighthead 10. The umbilical subassembly 16 spans the length of the liner 53. A heat exchanger 47 and coolant pump 48 collaborate to move fluid through the coolant hose return 26 and into the heat exchanger 47 to cool the fluid. Once fluid is cooled, the coolant is pumped back into the coolant hose inlet 23 for further cooling of the lighthead 10. The multiconductor cable 24 transmits power produced at a power supply and control 46 to the LED array 11 of the lighthead 10.

[0077] The lighthead 10 is towed via the umbilical subassembly 16 through the length of the resin impregnated liner 53 to initiate the cure of the impregnated resin by radiating the desired wavelengths of light on the inner surface of the liner 53.

[0078] In existing applications shown by Figure 10, instead, a prior art lighthead 10A absorbs heat, which is captured by an air stream, rather than by coolant in the present invention. The air exits into the interior of the host pipe 49 and the liner 53 to be vented tothe atmosphere outside the host pipe 49. Compressed air is produced at an air compressor 48A using the atmosphere as the air source, and an air dryer 50A removes water from the compressed air so as not to contaminate the LED Array with moisture or fog the glass cover 12.

[0079] Figures 12-13 show the alternative lighthead 200 with elements of its housing body 39A, the design of which facilitates a number of novel concepts for cooling a highly powered lighthead for application in CIPP repair. The body 39A, best made of a high heat conducting material such as aluminum or an alloy thereof, is generally cylindrical in shape. As with lighthead 10 and housing body 39, the body 39A has a number of mounting flats 41. A dozen flats 41 maybe used to provide area to achieve the light output desired to cure pipes in the 4” range. Other numbers of flats 41 may be used. Each flat 41 is used to mount an LED array 11.

[0080] The body 39A comprises a rear flange 210. The rear flange 210 bears against a sealing O-ring that is compressed by the tailcap 18 when attached to the body 39Aby threads 212. A coolant supply port 214 and return port 216 attach to coolant supply 23 and coolant return 26 (FIG. 18), respectively. The supply and return ports 214, 216, are found in a recessed counterbore 218 which allow fittings to sit deeper within the housing body 39A. A wire port 220 provides a passage 222 for the multiconductor cable 24 to pass to the front of the body 39A.

[0081] Figure 14-17 show the passages of each of coolant supply, coolant return, and the cable. All (3) ports 214, 216, 220 run more or less longitudinally with the body 39A axis.

[0082] Figures 15-16 show details of the coolant supply routing. Coolant enters at port 214, entering a supply port passage 230. Supply port passage 230 conducts cold coolant to the coolant chamber 27. The coolant chamber 27 has transfer ports 232 which pass the coolant from the coolant chamber 27 to an outer coolant chamber 240.

[0083] As shown, coolant chamber 27 is tubular in its form with an inner diameter formed by the wall of the wire passage 222 and an outer diameter that is the inner wall of the outer coolant chamber 240. Coolant chamber 27 serves as a reservoir to feed the coldcoolant to the front of the outer coolant chamber 240 before it is returned to the heat exchanger located above ground.

[0084] Once entering outer coolant chamber 240, the cold coolant is exposed to a gauntlet of flow guiding features that include bulkhead features 242. The bulkhead features 242 force the coolant flow to come close to the inner wall of the outer coolant chamber 240. The inner wall is opposite the flats 41 which mount the heat generating LED Arrays 11.

[0085] After passing over a bulkhead feature 242, the now slightly warmer coolant swirls about in an eddy pocket 244, formed behind the bulkhead feature 242 for the purpose of mixing to achieve a uniform coolant temperature. An eddy pocket 244 is found between adjacent pairs of bulkhead features 242.

[0086] The coolant finds its way over the next bulkhead feature 242 and the process is repeated until it reaches the coolant return passage 246 which leads to the return port 216 to which the coolant return line 26 (FIG. 18) is attached.

[0087] Figure 17 details the passage 222 through which the multiconductor cable 24 passes on its way from the umbilical subassembly 16 to the front of the lighthead assembly 200. The wire port 220 initially is off the central axis to allow additional space for the components related to the coolant path to be mounted. Once past the fitting connections the wire passage 222 returns to the central axis of the body housing 39 A.

[0088] The multiconductor cable may include connections which pass through a port 250 to allow conductors to be used for sensors 202 (FIG. 12) and the LED arrays 11. The port 250 and the passage 222 may be sealed by a wire seal 252. The wire seal 252 may also compress and clamp an elastic cork that surrounds the conduit 24. The conduit 24 terminates in a camera pocket 254 in which the camera 14 is seated.

[0089] Figure 18 shows the first end of the umbilical subassembly 16. The umbilical subassembly 16 may run for 50 to 100 meters in length, and includes the coolant supply line 23, coolant return line 26 and multiconductor cable 24.

[0090] With reference to Figures 19-23, a mobile cart 100 is shown for use with the lighthead 200. The mobile cart 100 has a frame 102 that extends from the ground tohandlebars 104. Wheels 103 and stabilizer pads 105 enable maneuvering of the cart 100 about a job site. A plastic drum 101 is provided, into which the umbilical subassembly 16 will be wound from or into during deployment or retrieval of the lighthead 200.

[0091] A propulsion unit 111, here, a small motor, pulls the lighthead 200 via the umbilical subassembly 16 at a regulated and predetermined rate through the host pipe to get an effective cure. The cart 100 may include a monitor 106 for providing information and control for the operator and an electronic control housing 107 which may contain a CPU and other electronics to achieve that control.

[0092] A fan 109, which may be electrically powered, is affixed to the frame 102 on the central axis of the drum 101. The frame 102 includes a shroud feature 110 that covers much of the finned area of a heat exchanger 108. Note that while the heat exchanger 108 rotates, it is mounted to the central hub (not shown) which is bolted to the frame 102.

[0093] While the heat exchanger 108 is shown as being disposed between the drum 101 and the fan 109, other orientations may work as well. For example, the drum 101 could overlap the heat exchanger 108 by having air flow through both elements and out a hole in the drum 101. The drum 101 contents - that is the umbilical 16 - maybe stacked radially about the heat exchanger 108. The primary advantages of the heat exchanger 108 are that it is thin and rotatable with the drum, to enable simple connections with the umbilical 16, and that fluid within it moves at a slow flow rate to increase the efficiency of heat exchange.

[0094] A second end of the umbilical subassembly 16 has an exposed coolant supply line 23 and coolant return line 26. The supply and return lines plumb into a manifold 113 which is attached to connectors 114. While the umbilical subassembly 16 is contained primarily inside the drum 101, the second end of the umbilical subassembly 16 with coolant return and supply lines 23, 26 uses a slot 112 to gain access to the manifold 113.

[0095] In Figures 20-22, the drum of the cart 100 is removed, allowing the heat exchanger 108 to be shown in detail. Visible is the pancake heat exchanger 108, local coolant pumping circuit (including coolant pump 121), and frame 102. The hub 116 has its axis of rotation called out as 123. A heat exchanger labyrinth plate 112 is shown. Coolantenters the heat exchanger 108 via an inlet port 117 which attaches to a heat exchanger inlet line 118.

[0096] In Figure 23, the fluid path 135, 136, 137 is shown. Coolant from the inlet port 117 enters a hot side coolant passage 135. The hot side passage 135 travels in a serpentine fashion within the pancake exchanger 108, exchanging heat with the ambient air as it travels through passages which may be less than an inch wide and less than a quarter of an inch deep.

[0097] Other dimensions maybe used depending upon cooling needs and flow rate. A passage transfer 137 moves the coolant to the opposite side of the exchanger where the coolant then winds through the cool side passage 136, exchanging heat with ambient air. An outlet port 120 receives cooled coolant, which enters an outlet line 119 for transport back to the umbilical subassembly 16 and lighthead 200.

[0098] The drum side of the heat exchanger labyrinth plate 112 may be relatively feature free other than the coolant pump 121 and coolant ports 117 and 120.

[0099] Given an exemplar coolant flow rate of .12 gallons per minute, the large cross section of the passages 135, 136, 137 produces a low flow velocity, meaning the coolant will spend an extended amount of time in the heat exchanger 108. Longer transit time allows the coolant to approach the ambient air temperature more closely. Passage dimensions may produce a nominal velocity of less than 15 ft / minute, for example, 11 ft / min, quite slow for a coolant velocity while in a heat exchanger 108.

[0100] Given the long length of the serpentine passages, the coolant may spend, for example, approximately 47 seconds within the cooler from entry to exit. The inlet side where the hot coolant flows in the hot side coolant passage 135 is short, taking advantage of the higher temperature differential to shed heat quickly. Conversely, the cold side coolant passage 136 is somewhat longer, giving the coolant additional time to approach ambient temperatures with the handicap of a lower differential temperature. By making the sides of the serpentine passages 135, 136, 137 non-symmetrical, the heat exchanger 108 maybe optimized for heat transfer conditions.[ooioi] Figure 21 shows heat exchanger 108 isolated from the remainder of the cart too. Fasteners 127 clamp together the inner and outer peripheries of a finned plate 124 to the labyrinth plate 122, compressing the O-ring found in groove 138 (see FIG. 23) to seal the coolant into the heat exchanger 108. A stationary hub face 129 bears against the frame 102 bracket and is secured to the bracket by fasteners that thread into holes 125. The hub face 129 has a control wire port 141 through which wires coming from the slip ring located inside hub 116 pass and continue through the frame 102 tubing to arrive at the control box 107. The heat exchanger 108 is secured to the rotating portion of the hub 116 via fasteners 126. The coolant pump 120 is secured to the finned plate 124 by fasteners 129. Fins 128 provide meaningful surface area for the fan 109 to blow or draw air over the passageways 135-137 and remove heat from the coolant.

[0102] Figure 22 shows an edge view of the pancake heat exchanger 108. The drum clamp thread 133 is used with a large hand tightened nut (not shown) to secure the drum 101 to the hub 116. A friction brake 130 is actuated to prevent the drum 101 from spinning too quickly when umbilical subassembly 16 is being pulled from it.

[0103] An electrical connector 132 joins the multi conductor wire 24 of the umbilical subassembly 16 to the slip ring circuits located inside the hub 116.

[0104] With reference now to Figures 24-28, the lighthead train 300, comprising individual lightheads 310, is shown. Trains are often used in operations where there is a considerable amount of resin in CIPP liners which need to be cured. Such applications require a large amount of light to initiate the curing of the resin.

[0105] Coolant can be routed through the multiple lightheads 310, which are positioned end-to-end. Preferably, upon reaching the forwardmost lighthead, the coolant direction is reversed and allowed to flow through the body of each lighthead 310, picking up waste heat generated by lights 312.

[0106] While lights 312 may be LED arrays, as in previous embodiments, light trains are often used in ultraviolet (UV) resin cured CIPP processes. Therefore, the lights 312 inlighthead train 300 applications maybe arg on / mercury plasma gas, or other mechanisms for producing UV light. LED arrays may also be used, as shown in the Figures.

[0107] A series arrangement, such as in the lighthead train 300, may pose difficulties in cooling, as the coolant’s temperature increases upon each successive heat exchange with a lighthead 310. This may be remedied by dividing flow of coolant at each lighthead 310, such that a percentage of low temperature coolant is directed into each lighthead 310, such that higher temperature coolant that has already absorbed heat from upstream lightheads may be brought to a moderated temperature.

[0108] With reference to Figures 24-28, the lighthead train 300 comprises three individual lightheads 310. Each lighthead comprises a body 314 on which the array of lights 312 are situated. Each lighthead 310 is connected to one or more adjacent lightheads by a link 316. The link 316 contains a conductor wire 318 and coolant line 320. The coolant line 320 has a bend 322 when it exits the forwardmost lighthead 310.

[0109] After leaving the bend 322, coolant enters the body 314 of each lighthead 310 in order to reduce the heat generated by the lights 312. A return line 324 passes the coolant between lightheads 310 and then out the back of the rearwardmost lighthead. An umbilical, similar to umbilical conduit 17 (not shown in Figures 24-28) maybe utilized to enclose lines 318, 320, 324. The conduit may then be attached to a drum 101 and heat exchanger 108.

[0110] Because lighthead trains 300 are often used in larger pipes, a wheel frame 330, supporting wheels 331, provides mobility for each lighthead 310. Other mobility devices may be used without departing from the spirit of the invention, including powered devices, tracked devices, and the like.. In addition, as with other lightheads shown in this disclosure, a protective, transparent cover maybe in place about the lights 312.

[0111] As shown in Figures 22 and 23, the link 316 includes a spherical joint 332 which enables connection to each lighthead 310 at a spherical pocket 334 formed in the body 314. An internal passage 336 passes the conductor wire 318 and coolant line 320 through the body 314.[ooii2] The body 314 comprises an end cap 340 at each end. The end cap 340 maybe coupled or threaded to make up the body 314 assembly. As best shown in Figure 24, the end cap 340 has a fitting 342 which allows coolant to enter the body 314 from a return line 324. The fitting 342 is in communication with a passage 344 in the end cap 340. The passage 344 may angle through the end cap to a coolant gallery 346. The gallery 346 is sealed on each side by O-rings or other seals, and the body 314 has longitudinal passages 348 within the gallery 346 which allow fluid to pass to an internal reservoir 350.

[0113] Use of the annular gallery 346 with distributed passages 348 allows a wire or other conductor to pass to the light array 312 from the conductor wire 318. Passage 349 may be one such passage for a conductor. Coolant within the internal reservoir 350 wets the inwardly-facing wall 352, such that heat generated by the light array 312 maybe transferred to slow-moving coolant therein. In addition, features such as the bulkhead features 242 may be utilized as discussed previously.

[0114] Light train systems, such as the light train 300, may not use a rotating cart like other lighthead systems. Due to this, it is possible to utilize a radiator or heat exchanger that does not rotate. However, principles taken from the pancake heat exchanger 108, as used with cart 100, are still illustrative as to the cooling of fluid in a fluid loop light train such as that shown in FIG. 24.

[0115] The various features and alternative details of construction of the apparatuses described herein for the practice of the present technology will readily occur to the skilled artisan in view of the foregoing discussion, and it is to be understood that even though numerous characteristics and advantages of various embodiments of the present technology have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the technology, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts within the principles of the present technology to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

CLAIMS:

1. A system for cured-in-place pipe repair comprising: a lighthead comprising a plurality of light emitting diodes, the lighthead including a cooling chamber; an umbilical attached to the lighthead, the umbilical comprising: an electronic cable connection configured to provide power to the plurality of light emitting diodes; a coolant supply line configured to provide liquid coolant to the cooling chamber; and a coolant return line configured to receive liquid coolant from the cooling chamber; and a heat exchanger, configured to receive liquid coolant from the coolant return line and to return liquid coolant to the coolant supply line.

2. The system of claim 1 further comprising: a mobile cart, comprising: a rotating drum; and a frame, supporting the rotating drum; wherein the umbilical is configured for rotational storage and deployment on the rotating drum.

3. The system of claim 2 wherein the heat exchanger is attached to the rotating drum and rotates therewith.

4. The system of claim 3 further comprising a pump, wherein the pump rotates with the rotating drum and is configured to move the liquid coolant through the coolant supply line, coolant return line, and heat exchanger.

5. The system of claim 2 wherein the mobile cart further comprises a fan supported on the frame, wherein the heat exchanger is disposed between the rotating drum and the fan.

6. The system of claim 5 in which the heat exchanger comprises a serpentine coolant path and a plurality of fins in conductive relationship to the serpentine coolant path.

7. The system of claim 6 in which the fan is configured to direct air across the plurality of fins along an axis of rotation of the rotating drum.

8. The system of claim 6 in which the serpentine coolant path comprises: a hot side coolant passage disposed on a first side of the heat exchanger; and a cold side coolant passage disposed on a second side of the heat exchanger; wherein liquid coolant is configured to have more residence time in the cold side coolant passage than in the hot side coolant passage.

9. The system of claim 1 in which the heat exchanger is disc shaped.

10. The system of claim 1 in which the liquid coolant comprises a mixture of water and ethylene glycol.

11. The system of claim 1 in which the lighthead comprises: an inner coolant chamber in communication with the coolant supply line; and an outer coolant chamber, connected to the inner coolant chamber by one or more transfer ports, wherein the outer coolant chamber comprises a plurality of bulkhead features, each of the plurality of bulkhead features configured to force the liquid coolant to a position proximate one or more of the plurality of light emitting diodes.

12. The system of claim 11 in which an eddy pocket is formed between adjacent pairs of the plurality of bulkhead features, wherein the eddy pockets are configured to provide mixing for the liquid coolant to achieve a uniform temperature.

13. A method of cooling a light array in a lighthead for use in a CIPP curing system, comprising: deploying the lighthead into a pipe, wherein the lighthead is attached to a rotating drum by an umbilical; illuminating the lighthead using the light array to cure a liner on an inner surface of the pipe; providing a low temperature liquid coolant to the lighthead through the umbilical; cooling the light array with the low temperature liquid coolant; removing a high temperature liquid coolant from the lighthead through the umbilical; placing the high temperature liquid coolant into a heat exchanger located proximate the rotating drum, thereby returning the coolant to its low temperature condition; and thereafter, returning the low temperature liquid coolant to the lighthead through the umbilical.

14. The method of claim 13 in which the heat exchanger is attached to and rotationally fixed with the rotating drum.

15. The method of claim 13 further comprising the step of forcing air over a plurality of fins, the plurality of fins attached to the heat exchanger.

16. The method of claim 13 wherein the heat exchanger is disc-shaped and thinner than the rotating drum.

17. The method of claim 13 further comprising the step of providing power to the light array through the umbilical.

18. The method of claim 13 further comprising: after curing of the liner is complete, storing the umbilical on the rotating drum.

19. The method of claim 18 in which the heat exchanger is attached to and rotationally fixed with the rotating drum.

20. The method of claim 13 in which the high temperature liquid coolant within the heat exchanger is cooled by a refrigerated coolant.

21. The method of claim 13 in which coolant passes through the heat exchanger at a flow rate of less than 15 feet per minute.

22. The method of claim 13 wherein the step of placing the high temperature liquid coolant into the heat exchanger comprises: providing the high temperature liquid to a first side of a serpentine path; forcing the high temperature coolant along the serpentine path to a second side of the serpentine path; and forcing air over the serpentine path, thereby removing heat from the high temperature coolant.

23. The method of claim 22 in which the first side of the serpentine path and second side of the serpentine path are not symmetrical.

24. The method of claim 22 in which the serpentine path has a cross-section of less than one-quarter of a square inch.

25. The method of claim 13 wherein deploying the lighthead in the pipe comprises: deploying a lighthead train comprising a plurality of the lightheads into the pipe, each of the lightheads being connected by a coolant supply line and a coolant return line.

26. The method of claim 25 in which the light array comprises an ultraviolet light source.

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