WO2005020285A2

WO2005020285A2 - Extrusion thermo-electric temperature control unit

Info

Publication number: WO2005020285A2
Application number: PCT/US2004/026668
Authority: WO
Inventors: Michael R. Bonner
Original assignee: St. Clair Systems, Inc.
Priority date: 2003-08-18
Filing date: 2004-08-18
Publication date: 2005-03-03
Also published as: WO2005020285A3

Abstract

The present invention provides a method of manufacturing a cooling device, comprising the steps of: extruding an elongate hollow body having a plurality of internally projecting, longitudinal fins; cutting a plurality of sections from the elongate hollow body; positioning the sections in substantially parallel, longitudinal alignment; placing at least one thermo-electric heat pump chip between the sections, and connecting the chip to a power supply.

Description

"EXTRUSION THERMO-ELECTRIC TEMPERATURE CONTROL UNIT"

TECHNICAL FIELD The present invention relates generally to temperature control devices and apparatuses, and more particularly to such a device or apparatus wherein a plurality of hollow extrusion bodies are positioned in thermal communication, and a thermal transfer fluid is circulated through at least one of the bodies to facilitate heat transfer therebetween in cooperation with a solid state thermo-electric heat pump chip.

BACKGROUND OF THE INVENTION Temperature control is increasingly important in the electronics field. Proper operation of a wide variety of electronic devices depends upon maintaining their temperature within a particular range. Temperature fluctuations beyond a certain range can disrupt accurate system operation, or worse, damage sensitive, expensive components. Similarly, certain steps in manufacturing electronic devices and components may require effective process temperature control. Various air-cooled systems, cold plates, and similar designs are familiar technology, and have long been the standard for temperature regulation in many industrial processes and in cooling systems for electronic equipment. Fans of various sizes have frequently been used for carrying waste heat from electronic and other devices. For example, a fan may be mounted such that air can be blown or drawn across electronic components and/or heat-conducting materials (heat sinks) mounted in thermal communication with chips, boards, circuitry, etc. Various liquid-based systems have also been developed. In a typical known system, a heat sink having internal plumbing is positioned in thermal communication with a device whose temperature is to be regulated. Thermal transfer fluid can be pumped or otherwise circulated through the heat sink, and excess heat thereby eliminated from the system. The thermal transfer fluid can itself be cooled, for example, by circulating the fluid through coils exposed to ambient, or by blowing an air stream across conduits carrying the fluid. In some instances, the fluid itself can be chilled or heated prior to introduction into the plumbing to enhance the system's temperature control properties. Although various known systems have performed well over the years, they are not without significant drawbacks. Engineers continue to search for smaller, lighter and more efficient and effective means for temperature regulation of electronic equipment. Likewise, increasingly sensitive materials are being used in electronics manufacturing, and there continues to be a need for improved process temperature control in various manufacturing areas. For example, surface mount manufacturing utilizes various pastes and adhesives that are preferably applied at specific viscosities. Temperature control can be critical to maintaining an appropriate viscosity for application of the materials, often requiring maintenance of the materials within a range of only a few degrees. In a typical operation, application syringes or other relatively small vessels are maintained within the desired temperature range, then placed onto the dispensing apparatus just prior to beginning a production run. These systems generally require a relatively complex and bulky temperature controlled storage apparatus close to the production line. Other types of electronics manufacturing also require specific viscosities for application of various materials. For instance, conformal coatings are used to protect various portions of circuit boards; however, spraying onto certain electronic components such as potentiometers and connectors can be undesirable. Thus, spray pattern and material flow after spraying must be carefully controlled, usually by monitoring and regulating the coating material's viscosity prior to application. Some recently developed devices, for example, laser diode sensors/scanners, do not operate properly unless their temperature is maintained within a relatively narrow operating range. Fluctuations in temperature can affect output wavelength of the laser, and thus disrupt the reliability of system operation. Although conventional temperature control systems have been applied to lasers and other temperature-sensitive devices, there has heretofore been a need for development of still smaller, lighter and more efficient systems. Other important temperature control applications include foam-in-place gasket operations, biomedical applications, boxing line adhesive dispensing. BRIEF SUMMARY OF THE INVENTION It is an object of the present invention to provide a compact, improved means for temperature control. In one aspect, the present invention provides a thermo-electric temperature control device preferably comprising a first extrusion body, and a second extrusion body mounted in thermal communication with the first extrusion body. A heat pump chip is preferably positioned between the first and second extrusion bodies, and facilitates heat transfer therebetween. A thermal transfer fluid is circulated through at least one of the extrusion bodies, and conducts heat between a target device in thermal communication with the first extrusion body. In another aspect, the present invention provides a modular thermoelectric temperature control system preferably comprising a first extrusion body through which a thermal transfer fluid is circulated. At least one additional extrusion body is preferably mounted in thermal communication with the first extrusion body. Air or another suitable fluid is preferably circulated through the at least one additional extrusion body. In still another aspect, the present invention provides a method of manufacturing a thermo-electric temperature control device, preferably comprising the steps of: extruding an elongate hollow body; cutting a plurality of sections from the elongate hollow body; positioning the sections in substantially parallel, longitudinal alignment; and placing at least one thermally conductive electrical device between the sections.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross section of an extrusion according to the present invention; Figures 2a and 2b illustrate end and side views, respectively, of a cap for an extrusion according to the present invention; Figure 3 is an assembly view in cross section of a temperature control assembly according to the present invention; Figures 4a and 4b illustrate end and side views, respectively, of a traced block; Figures 5a and 5b illustrate end and side views, respectively, of a profile traced cover. DETAILED DESCRIPTION The present invention broadly comprises a thermo-electric temperature control system that includes a plurality of substantially similar hollow extrusion bodies in thermal communication via one or more solid state thermo-electric heat pump chips. In a preferred embodiment, the extrusion bodies are cut into the desired lengths and volumes from a single extrusion. At least a first of the extrusion bodies preferably serves as a fluid "tank," and is substantially filled with a thermal transfer fluid, while one or more additional extrusion bodies preferably carry air. Extrusion bodies cut from the initial, single extrusion can serve either function, i.e. carrying thermal transfer fluid or air, without the need for substantial modifications. The thermal transfer fluid-filled extrusion body serves as a thermal mass for conducting heat into or out of a system or device, hereafter "target device," whose temperature is to be regulated. As used herein, the terms "thermal communication" and "thermal contact" should be understood to encompass a variety of physical mounting arrangements. In a preferred embodiment, a heat exchanger is mounted in thermal communication with the device or system whose temperature is to be regulated. Thermal transfer fluid is preferably circulated between the tank and the heat exchanger, providing or removing heat from the target device as needed. Air or another fluid is preferably circulated through at least one additional extrusion body, in thermal communication with the tank, and can adjust the temperature of the thermal transfer fluid in the tank, facilitated by action of the heat pump chip. Alternative embodiments are contemplated in which the tank(s) is/are placed directly in thermal contact with the target device, dispensing with the need for additional conduit for transferring the thermal transfer fluid. It is unnecessary that the target device(s) be in actual physical contact with the tank or heat exchanger, so long as the tank or heat exchangers used are mounted such that heat can be transferred between the device(s) and the thermal transfer fluid. Thus, air gaps, thermal greases, tapes, thermally conductive polymers, etc. might be positioned between the extrusion body or heat exchanger and the target device. It is contemplated that the present device will find primary application in systems wherein it is necessary to carry excess heat away from an electronic or other device, but the present invention is not thereby limited to such an application. Embodiments are also contemplated in which the present invention is utilized to carry a heated fluid to a device, thereby increasing its temperature. Further still, systems are contemplated wherein both heated and chilled fluid are provided, and can be selectively supplied to the target device as needed to maintain the temperature within the desired range. Thus, references made herein to removing heat from the target device should not be taken to limit the present invention solely to applications wherein the temperature of the target device is lowered. The thermal transfer fluid may be optionally chilled or heated prior to introduction into the heat exchanger positioned in thermal communication with the target device. Similarly, although it is contemplated that the present invention will be primarily applied to temperature control in the electronics field, other applications such as temperature control in the biomedical field are possible. For example, in many biomedical procedures such as blood dialysis or plasma harvesting it is desirable to maintain the temperature of body fluids within a relatively narrow range, a goal that may be effectively achieved using a system constructed in accordance with the present invention. References herein to "device" or "target device" should therefore be understood to encompass not only working electronic or mechanical devices, but other materials such as fluid dispensing units, blood or plasma transfer tubes, fluid reservoirs, etc. All the component parts of the present invention are manufactured from known materials and by known processes. Referring to Figure 1, there is shown a cross section of an extrusion 10 according to the present invention. Extrusion 10 is preferably formed from aluminum, copper or some other relatively highly heat-conductive metal, however, it should be appreciated that any material capable of being extruded into the desired shape, and having the desired heat conducting properties might be utilized in constructing the present invention. Extrusion 10 includes an extrusion body 12 that is preferably an elongate, hollow fluid-carrying conduit having an internal fluid space or reservoir 15. In a preferred embodiment, body 12 is manufactured having dimensions ranging from 5-6 inches in cross sectional width, down to less than about Vz inch in cross sectional width. For applications requiring relatively greater or lesser fluid volumes, the width or length of body 12 can be adjusted accordingly. Body 12 is preferably substantially bilaterally and radially symmetrical. Body 12 preferably further includes a plurality of internally extending longitudinal fins 14 that impart additional surface area for enhancing heat transfer between fluid carried through fluid space 15 and body 12. Turning to Figure 3, there is shown in cross section a temperature regulating apparatus 20 in accordance with the present invention. Apparatus 20 preferably includes a plurality of substantially identical extrusion bodies 110a and 110b, similar to extrusion 10 of Figure 1. A first of the extrusion bodies 110a preferably carries the thermal transfer fluid. Water is the most preferred thermal transfer fluid, however, other suitable fluids such as water, various oils, propylene glycol, etc. may be used with the present invention. Electrically conductive as well as electrically insulative fluids may be used. The second extrusion body 110b carries air to remove heat transferred from first body 110a. Thus, first body 110a can be positioned directly in thermal contact with a target device(s) that is to be heated or cooled, or it can be mounted such that it carries fluid that has previously passed through a heat exchanger (not shown) positioned in thermal contact with the target device. An insulation layer 16 may be positioned around first body 110a if desired. In a preferred embodiment, bodies 110a and 110b are mounted such that two longitudinal bosses 122a and 122b, one on each of bodies 110a and 110b, respectively, are positioned proximate and substantially a constant distance from each other along at least a portion of the length of bodies 110a and 110b. As illustrated in Figure 3, each of the extrusion bodies 110a and 110b are substantially rectangular and bilaterally and radially symmetrical. Accordingly, each extrusion body preferably includes a longitudinal boss 122 protruding from each of four faces of the extrusion. This region of increased thickness provides a surface suitable for machining. As such, the region can be drilled, tapped, vented, etc., to provide for insertion of temperature probes, float switches, or other devices, as shown in Figure 3. Similarly, the bosses on faces of the extrusion bodies remote from the boss aligned with the other tank can be used for attaching mounting brackets, fasteners, and similar members. In a preferred embodiment, a solid state thermo-electric heat pump chip 130 is positioned such that a first face of the chip contacts boss 122a, and a second face of the chip contacts boss 122b. A thermo-electric chip is generally a collection of 127 peltier diodes sandwiched between two ceramic plates. Numerous brands, types and styles of such chips are well known in the art, and readily commercially available. The diodes channel heat from one side of the chip to the other when a DC current is applied thereto. The direction of heat transfer is determined by the polarity of the DC current. Thus, when current of a first polarity is passed through chip 130, heat will be drawn from the fluid in first body 110a, and in thermal contact with boss 122a on one side of the chip, and moved via chip 130 to body 110b and air or another fluid therein. When current of the opposite polarity is passed through chip 130, heat will be transferred in the opposite direction. One chip and the associated power components are preferably used for approximately each 5" length of extrusion body. A muffin fan 140, well known in the art, is preferably positioned at an end of second extrusion body 110b, and blows ambient air therethrough. Those skilled in the art will appreciate that any suitable means for driving air through second body 110b might be used, such as a compressed air supply. Further still, it is not necessary that air be used at all. Alternative embodiments are contemplated wherein both of first and second extrusion bodies 110a and 110b carry thermal transfer fluid. Where it is desirable to enhance temperature control of fluid in extrusion body 110a, an extrusion body such as body 110b can be positioned along a plurality of sides of body 110a. Thus, embodiments are contemplated wherein two, three or four air or other fluid-carrying extrusion bodies are positioned in thermal contact with body 110a. Such a design may be preferred, for example, where aggressive cooling of a single thermal transfer fluid-carrying circuit is desired. The bosses formed on multiple sides of the extrusion bodies facilitate modular assembly of systems having many potential designs. Similarly, rather than a plurality of air- carrying extrusion bodies mounted with a single thermal transfer fluid-carrying body, a plurality of thermal transfer fluid-carrying bodies might be mounted in thermal contact with a single air-carrying extrusion body. Such an embodiment may be preferred, for example, where it is desirable to provide several different thermal transfer fluid circuits, temperature controlled with a single air-carrying extrusion body. The aforementioned variations, in conjunction with a variable length of the extrusion bodies and either vertical or horizontal operation provides a virtually endless variety of configurations/capacities. In a horizontal configuration, various probes, sensors, etc. applicable to the present device can be positioned along the longitudinal bosses, as described above. For vertical applications, probes, sensors, etc. can be positioned in the caps, described below. Further still, by preferably separating the power supply, the present apparatus can be created as a stand alone module, or it may be tailored to a particular application, and manufactured integrally therewith. Turning to Figures 2a and 2b, there are shown a side view and end view, respectively, of a modular cap 150 for use with extrusion bodies formed according to the present invention. In a preferred embodiment, cap 150 is mounted over a gasket, and secured to an end of an extrusion such as extrusion body 110a or 110b of Figure 1. When two caps 150 are fitted over ends of an extrusion body, inlet and/or outlet fittings can be attached thereto, for example with a threaded engagement, to provide an enclosed tank for circulating the thermal transfer fluid. Alternatively, the fittings could be attached to cap 150 prior to its engagement with the extrusion body. Where it is desired to use the particular extrusion body for circulating air, such as body 110b from Figure 3, the cap need not be used. Cap 150 can be manufactured by either die casting aluminum or another metal, or by molding cap 150 from a plastic. Referring now to Figures 4a and 4b, there are shown end and side views, respectively, of a traced block 200 contemplated for use with the present invention. Block 200 is preferably constructed from a solid, machined piece of relatively highly heat conductive metal, although alternatives are contemplated wherein block 200 is manufactured from multiple pieces or from some other suitable material. A plurality of bores 210 are preferably formed substantially radially symmetrically about a central fluid delivery 220, which may be simply an additional bore through block 200, or a more complicated apparatus including a nozzle, valve, etc. In a preferred embodiment, a temperature regulating apparatus such as apparatus 20 of Figure 3, provides thermal transfer fluid for circulation through bores 210. Embodiments are contemplated wherein thermal transfer fluid is passed unidirectionally through bores 210, as well as embodiments wherein fluid is passed through certain of bores 210 a first direction, and is passed through other of bores 210 in an opposite direction. Turning to Figures 5a and 5b, there are shown end and side views, respectively, of a profile traced cover assembly 300 for applications similar to those contemplated for use with block 200 of Figure 4. Cover assembly 300 preferably comprises a hinged cover 310 and a plurality of fluid transfer profiles 312. Cover 310 is preferably molded plastic, but some other material might be utilized if desired. An insulating layer 330 may be positioned around cover 310. In a preferred embodiment, cover 310 is closed about a fluid delivery 320, such as a fluid conduit, and thermal transfer fluid is passed through profiles 312. Profiles 312 are preferably positioned in direct physical contact with the fluid delivery 320; however, cover 310 may be formed such that a gap remains between profiles 312 and fluid delivery 320 when cover 310 is closed. Such a gap may be filled, if desired, with a thermally conductive material. There are many such materials known in the art, and various greases, pastes, creams, and gels are readily commercially available. Further still, there are numerous dry, thermally conductive foams and tapes known in the art that may be applied, for example with a thermally conductive adhesive. The cross sectional geometry of profiles 312 may be tailored for particular applications. For instance, profiles 312 might be fashioned to have a relatively greater area of surface contact with a fluid delivery conduit than the examples in Figure 5, and a correspondingly flatter cross section. Similarly, larger or smaller profiles can be used to increase or decrease the fluid flow capacity, or the effective area of surface contact with the pipe, syringe, etc., depending on system requirements. The wall thickness of the profile along its side of contact with the pipe, syringe, etc. can also be adjusted to provide varying degrees of thermal conductivity. In general, embodiments utilizing fewer profiles are preferred in order to minimize the number of fluid connections in the system, however, fluid flow rates tend to decrease with increasingly flattened profiles, and wider profiles tend to be more challenging to manufacture. The embodiment pictured in Figure 5 utilizes three profiles, although this number might be varied for use in other applications. A variety of hinging means are contemplated for use in constructing i cover 310, for example, a thinned plastic strip formed integrally in molding cover

310, and attaching adjacent, thicker portions. Conventional hinges might also be used. Alternative embodiments are contemplated wherein cover 310 is formed from a plurality of shaped pieces that can be separately positioned about fluid delivery 320, and are not integrally connected. Profiles 312 are preferably formed such that they have a cross-sectional shape that substantially conforms with fluid delivery 320, optimizing the surface area of profiles 312 that contact fluid delivery 320. Profiles 312 may be formed by a variety of means, for example, the profiles may be extruded, stamped, roll-formed, molded, cast, milled or manufactured by some other process. Preferred metals for manufacturing profiles 312 include both ferrous and non-ferrous metals, although relatively soft metals such as copper or aluminum are particularly preferred. Softer metals tend to be easier to form to the desired shape, and often have a relatively greater thermal conductivity than harder metals. In addition to metals, embodiments are contemplated wherein thermally conductive plastics are used. In still another aspect, the present invention provides a method of manufacturing a cooling device, preferably comprising the steps of: extruding an elongate hollow body having a plurality of internally projecting, longitudinal fins; cutting a plurality of sections from the elongate hollow body; positioning the sections in substantially parallel, longitudinal alignment; placing at least one thermo-electric heat pump chip between the sections, and connecting the chip to a power supply. The size of the sections cut from the extrusion can be varied to provide relatively larger or smaller fluid volume systems. Moreover, the modular nature of the extrusion bodies used in systems according to the present invention allows thermo-electric temperature control units to be constructed relatively easily and inexpensively, needing fewer parts than many known systems. The present description is for illustrative purposes only, and should not be taken to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the scope of the present invention. Other aspects, features and advantages will be apparent upon an examination of the attached drawing Figures.

Claims

1. A device for the circulation of a thermal transfer fluid and the circulation of ambient air comprising: at least two extruded thermally conductive bodies, a first of said bodies containing said thermal transfer fluid and a second transfer fluid and a second of said bodies open to ambient air: and said at least two bodies thermally connected by a thermo- electric chip;

2. A method of manufacturing a cooling device, comprising the steps of: extruding an elongate hollow body having a plurality of internally projecting, longitudinal fins; cutting a plurality of sections from the elongate hollow body; positioning the sections in substantially parallel, longitudinal alignment; and placing at least one thermo-electric heat pump chip between the sections.