High throughput technology for heat pipe production

Abstract

Invention discloses technology of production of various heat pipes in a single technological step which requires no vacuum equipment.

Description

FIELD OF INVENTION

This invention discloses a technology that directly relates to methods of creation and manufacturing of devices classified as a heat pipe.

SUMMARY

Traditional processes of manufacturing a heat pipe include multiple steps:

(1) Creation of shell material

(2) Forming shell geometry

(3) Creation of wick

(4) Partial seal of assembly

(5) Evacuation of inner volume

(6) Disposition of refrigerant liquid

(7) Final sealing of the product

Several technological innovation has been disclosed in prior art to reduce complexity of the process. In U.S. Pat. No. 4,196,504 Eastman teaches how to reduce process of partial assembly via in place formation of the wick structure. His wick is formed by sintered powder inside the casing of the heat pipe. Yet this technique introduces additional step of sintering that make process more expensive.

In another U.S. Pat. No. 4,995,450 Geppelt, et al. teach to replace a wick with spiral groove s on the walls of the shell. While the process eliminates the step of wick assembly it make the product only suitable for lower location of a heat source which makes their invention limited to gravity heat pipe.

In another invention (U.S. Pat. No. 5,564,184) Dinh discloses approach that converts standard pipe fragments into shells having internal grooves and external fins in one operation. This technology merges steps of forming the shell and making the wick into one allowing for notable production benefits.

In U.S. Pat. No. 5,598,632 Camarda, et al. teaches to use removable fibers as a place holder for capillary and gas volumes of essentially a wick. Technology allows for simplification of wick making process and integrates it with partial assembly step.

Another technology is disclosed in U.S. Pat. No. 5,737,840, where Akachi teaches how to modify parallel micro channel array cavities into a single cavity by a mechanical process. This technology does not reduce number of operations, as it replace wick formation step with shell modification processes.

Yet another invention (U.S. Pat. No. 6,647,625) teaches how to increase heat pipe efficiency with integral formation of radiating fins and the pipe shell. This technology does not reduce production steps but provides some performance improvements.

In U.S. Pat. No. 6,745,825 Nakamura, et al. teaches alternative formation of the wick and shell yet introduces no reduction of processing steps.

In U.S. Pat. No. 6,863,117 Valenzuela teaches of new interface between the wick and the shell that increases heat pipe performance. This technology introduces additional steps in formation of the wick structure and partial assembly.

Yet another invention (U.S. Pat. No. 6,863,118) teaches how to construct a shell with integral wick by soldering together two preformed sheets. This technology combines shell formation wick construction and partial assembly into a single step, which allows for boost of production efficiency.

The objective of present invention introduces single step process that produces complete heat pipe devices. Technology merges all aforementioned steps into one step. This allows drastic reduction of production costs and makes possibilities for radically new products and applications.

DETAILED DESCRIPTION

FIG. 1 shows simplified design of production line. Figure excludes all elements not essential for understanding the method of the invention, some dimension may appear not in scale. This is done to make illustration more readable. Plurality of additions and alterations are allowable by the technology of this invention, those will be discussed with less details as it will be obvious how to implement them.

Production line comprises a single machine that from start to finish completes all operations are releases plurality of ready to use heat pipes. This machine is not robotic system that might be used in competitive technologies to assist in execution of multiple distinct production steps. The machine of this invention is continuous cycle system that uninterruptedly delivers heat pipes in form of either single continuous pipe of unlimited length (length limitations are imposed only by availability of deposited raw materials), or plurality of sequentially or simultaneously produces discontinuous heat pipes of identical or various lengths.

Machine shown on FIG. 1 resembles vertical extruder although the same design principles can be used for horizontal extrusion. Cylindrical tank 1 is utilized to liquefy and/or to hold raw material of the shell in its liquid form. Heater 3 and insulation 4 serve the same goal. Extrusion nozzle 2 secured in the cavity on the axis of the tank. Its shape and shape of the tank wall cavity serve creation of desired groove s on inner and outer walls of extruded material. FIG. 1 shows grooves on inner walls only, leaving the outer wall flat. This serves illustration purposes only as in practical application outer surface of the shell may have special groove patterns.

Center of the nozzle holds high pressure tube 16 that delivers refrigerant fluid of the heat pipe. Depending on the raw material temperature of the tank can reach several thousand degrees design provisions are made to reduce temperature of the tube. Fluid is supplied by high pressure precision pumps and in case of water as a refrigerant fluid this pressure can reach 300 bar. The liquid in the tube may reach over its critical state.

Another liquid pump is formed by rotor 19 and the tank cavity. Both the rotor and the cavity have taper thread of opposing orientations. Rotation of the rotor or the tank transfers liquefied raw material toward the extruder nozzle. Material solidifies when reaching cooler 7. The cooler temperature corresponds to softening point of the material. Its walls contain ports that serve as a gas or liquid bearing. Refrigerant liquid (in current state it is pressurized vapor) stabilized extrusion shape by supplying pressure on inside walls of the extrusion.

FIG. 1 shows optional second intermediate extrusion nozzle 10 that transforms shape of the extrusion. In current example extrusion has cylindrical shape after the first extrusion nozzle, then it transforms into flattered shape by the second nozzle. The tank suspension has an option for axial rotation. This rotation applied to tank and the first nozzle by means of chain transmission 6 and insulating table 5. The second nozzle remains stationary. The process thus creates spiral or zigzag or weave pattern of the grooves depending on the rotation pattern.

Press 12 utilizes various desirable stamps or rolls to indent or perforate continuous shell. In one example it creates mesh like welds between opposite walls of the shell, in other case it creates sealed slots arrays connecting opposite sides of the shell, any other patterns are possible. Inner volume of the press stamps/rolls maintained under the same high pressure as the refrigerant liquid/vapor. In preferred embodiment the stamp fuses opposite walls of the pipe into continuous seam. This insulates volume of upper part of the extrusion from its lower part. In practical applications more than one type of stamps or rolls can be sequentially arranged to execute welding, seaming, perforation, vulcanization etc.

Cooler 11 further reduces temperature of the extrusion. In preferred embodiment it cools it to ambient temperature that completely solidifies the shell 9. Pullers 22 assist in translation motion of the extrusion. Cutters 8 of the preferred embodiment are synchronized with position of the seam and separates insulated potions of the extrusion thus creating ready to use heat pipes 9.

Disclosed machine and technology unlike any other does not require vacuum. It uses degassed refrigerant liquid that might contain some residue of Helium (in special cases). During process startup short segments of the pipes are created that reduces concentration of ambient gases inside the extrusion as kⁿ, where k is ration or combine volume to dead volume and n is number of seams. This sequence allows quickly exterminate residual gases. Absence of evacuation steps and equipment makes the whole production very time and cost efficient.

This machine and technology is versatile. It allows manufacturing of heat pipes from broad range of materials including quartz, steel, other metals, glass, plastics, and rubber. With slight modification fiber reinforced materials can be used as well by disposing a sleeve or threads through extrusion cavity. Instead of thermal operations referred in this description chemical agents such as vulcanizing and polymerization agents can be disposed through the train of extrusion process to achieve the same result with polymeric and composite materials. Other modification can be made to allow for use of ceramic compounds where the material will be baked instead of cooling to make it solid.

The machine of preferred embodiment is tuned to produce short discontinuous heat pipes from glass. Each pipe has length of 25 mm to 100 mm, width of 2 mm to 10 mm, and height of 0.5 mm to 3 mm. FIG. 2 illustrates design of this pipes. Extrusion 1 with inner wall groove s 2 twisted around axial direction is transformed from round into flattened shape 3. Groove s on opposite sides form intersecting lines 4. When material of the shell is in soften state both sides are pressed against each other and form sintered two layer mesh. In this mesh capillary channels on opposite sides flow in direction of opposite edges 5. Groove s of opposite sides overlap in a way that interconnects all their volumes into single continuous volume. And this volume is in communication with volume of edges 5.

This inventive design allows for seamless formation of capillary wick structure. This wick has effective evaporator regions 6 on interface with edges 5. Each edge forms a tube 7 allowing for high efficiency vapor transfer. FIG. 3 shows some alternative extrusion designs achievable through the same technique. Top picture shows planar layout that may be extended to include more than three tubular features. Lower pictures shows star like formations where arbitrary number of rays could be created.

Interestingly enough the wick structures formed by technology of this invention can be presented by more than one type. Internal groove structure has been described here in grate details. Yet machine of the invention can utilize a spool of wick material such as metal or glass yarn, mesh sleeve or plurality of other materials placed on a spool. The spool can be sealed on axial channel as shown on FIG. 4. High pressure vessel 1 hermetically encloses spool 2 of wick material. Refrigerant fluid is provided by input pipe 3. The thread of the wick 5 material is disposed through output tube 4. The wick is submersed in refrigerant liquid. This assembly is placed into axial volume of preferred embodiment design. Alternatively a bead or pellets could be disposed the same way as the tape or the yarn, which will allow forming a wick from plurality of adjacent bead/pellets.

Yet another innovative wick construction can be originated from technology of this invention. This construction uses extrusion with smooth none-grooved inner walls. Processing of initial extrusion is identical to prior description with one notable peculiarity. The press or utilizes a pair of rolls or stamps that slightly offset each other thus creating lateral force along the surface of the shell in a way that opposite walls shifts in opposite directions. When a sequence of such fusion points is applied the inner space between opposite walls receives plurality of interconnected splits. Alternatively stamps with un-matching shape can be used to reproduce this effect (e.g. round against flat) as unequal expansion of adjacent walls will be introduced resulting in cited irregularities. Resulting structure is illustrated on FIG. 5. Upper wall 1 crimped relative to lower wall 2. They are fused together at points 4. Plurality of interconnected splits 3 form capillary plane that has sufficiently low channel height. Vapor channels are not shown on this figure. They are arranged the same way it was described on FIG. 2 and FIG. 3.

One of advantage of such technological approach is simultaneous addition of exterior corrugation. Increase of external surface area and irregular surface are advantageous to applications where heat pipe is embedded into volume of other materials as described in co-pending application Ser. No. 11/307,125.

FIG. 6 shows heat pipe segment that produces using aforementioned grooveless technology. The roller stamp in this case mergers opposite sides 1 and 2 of flattened extrusion. It punches through the walls forming sealed joins 5. Offset placement of the stamp also induces splits 3 that form interconnected volume of essentially wick. This volume is in connection with vapor channels 4 and 6. Number of vapor channels can be changed to suit specific design. This mesh like heat pipe was first disclosed in co-pending application. Present invention demonstrates effective method of its production.

Important notes on process tune-up:

• • Refrigerant pressure should be tuned according to temperature settings for partially cooled heat pipe. This adjustment allows supplying required amount of refrigerant to each heat pipe.
  • Wall thickness of the shell must be selected to allow sufficient flexibility at temperature of press and stamps/rollers. Counteracting refrigerant pressure must be taken into account, as it supports positive curvature of the shell.

Disclosed technology can be scaled up to production of large scale heat pipes and even rifle barrels, yet one of main benefits from invented technology is its ability to mass produce small discontinuous heat pipes in bulk quantities.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows simplified design of apparatus for production of heat pipes. Drawing was drafted in accordance with ANSI standards. Detail view B illustrated rotational manifold that supplies pressurized refrigerant liquid. Detail C focuses on extruder with pressure compensator.

FIG. 2 illustrates example of produced heat pipe design. Round profile extrusion (top) flattened to planar shape (center), where twisted shell forms intersecting overlapped channels (section A) and large diameter vapor cavities (bottom).

FIG. 3 shows alternative extrusion designs achievable through the same technique. Planar layout may be extended to include more than three tubular features (top). Star like formations with arbitrary number of rays could be created (center and bottom).

FIG. 4 shows sample design for thread spool enclosure. It allows embedding of additional fibrous components into heat pipe structure.

FIG. 5 shows design produced with stamps of un-matching shapes.

FIG. 6 shows heat pipe segment that produces using aforementioned groove less technology.

Claims

1. A method of extrusion of closed profile wherein a compound or mix is disposed at the time of extrusion into inner volume of this extrusion in either liquid or gaseous or transient state.

2. A method of claim 1 wherein inner wall of said profile receives grooves due to said extrusion process.

3. A method of claim 2 wherein said grooves lines are twisted in uniform or zigzag or weave pattern around preferred direction of said extrusion.

4. A method of claim 1 wherein said profile is reshaped to different profile with nearly the same length, and said second profile has smaller area.

5. A method of claim 3 wherein said twist is uniform and the material strength of said extrusion and its wall thickness is sufficient to sustain lunch cycle of projectile utilizing either chemical combustion or compressed gases or electro magnetic propulsion.

6. A method of claim 1 where in addition to said compound a solid material in form of either continuous tape or string or similar, or in form of beads or pellets is disposed at the same time of extrusion.

7. A method of claim 4 wherein there is a plurality of location of said extrusion that are joint to plurality of other locations on the extrusion in a way that plurality of interconnected volumes is formed.

8. A method of claim 7 wherein some of said joints form interconnections of outer surface of said extrusion.

9. A method of claim 3 wherein said profile is reshaped to different profile with nearly the same length, and said second profile has smaller area, and groves of adjacent segments of inner surface are not parallel.

10. A method of claim 9 where in there is a plurality of location of said grooves that are joint to plurality of other locations on the extrusion in a way that plurality of interconnected channels is formed.

11. A method of production of heat pipe devices wherein said complete and functional devices are created without use of vacuum or vacuum pumps.

12. A heat pipe device wherein a capillary volume formed by plurality interconnected voids is formed by two essentially parallel and essentially smooth surfaces that are fused together in plurality of locations.

13. A heat pipe device produced according to claim 1 wherein said extrusion is segmented by plurality of seams into plurality of sealed discontinuous volumes.

14. A heat pipe device of claim 13 wherein material of said extrusion is metal.

15. A heat pipe device of claim 13 wherein material of said extrusion is glass.

16. A heat pipe device of claim 13 wherein material of said extrusion is ceramic.

17. A heat pipe device of claim 13 wherein material of said extrusion is polymer based.

18. A heat pipe device of claim 13 wherein material of said extrusion is fiber reinforced composite.

19. A heat pipe device of claim 13 wherein material of said extrusion is inorganic composite.

20. A method of claim 1 wherein said mix contains at least one element that accelerates chemical processes in material of said extrusion.