System and method for vacuum infusion

Abstract

A vacuum impregnation system and method as follows: subjecting a part to a vacuum, immersing the part in a polymer impregnation liquid, and applying positive pressure to the part to introduce the polymer impregnation liquid into part porosity, releasing the pressure to atmospheric pressure, and preferably hardening the polymer impregnation liquid without an active polymerization step.

Description

Technical Field

[0001] The present invention generally relates to the field of vacuum impregnation systems and methods, which subject a part to a vacuum, immerse the part in an impregnation liquid, and apply positive pressure to the part to introduce the impregnation liquid into the pores of the part, wherein the impregnation liquid hardens in the pores of the part. Background Technology

[0002] Vacuum impregnation systems are used to seal holes and small gaps in articles (such as individual parts or assembled parts). Such seals can, for example, reduce or prevent the ingress of water, oil, dirt, and other contaminants into the part or assembly, and help prevent corrosion. Articles can include cast metals and other materials, including combinations of metals and plastics. Generally, vacuum impregnation is performed by placing the article under a vacuum, bringing the article into contact with an impregnation liquid, and then optionally applying positive pressure to facilitate the movement of the impregnation liquid into holes and gaps. Vacuum impregnation methods can be classified into two groups: dry vacuum and wet vacuum.

[0003] Dry vacuum impregnation refers to a process where a part is placed in a sealed chamber containing a gaseous environment (such as ambient air), and a vacuum is applied to remove the gaseous phase from the chamber (including from pores and gaps in the part); then, while maintaining the vacuum, a sealant is transferred from a reservoir into the sealed chamber; when the vacuum is released, the sealant is drawn into the pores, and unused sealant is returned to the reservoir. Dry vacuum impregnation may include the following steps: after releasing the vacuum, applying a positive pressure, typically about 4-7 bar (400-700 kPa), and maintaining this pressure for a selected time to allow the sealant to penetrate the pores.

[0004] Wet vacuum refers to immersing the part in an impregnation liquid within a vacuum chamber, then applying and maintaining a vacuum until all air is removed from the reservoir and sealant. The challenge of wet vacuum is overcoming the hydraulic pressure head of the sealant within the vacuum chamber, resulting in a smaller negative pressure over orifices and gaps. A drawback is the trapping of a limited amount of air in the orifices, which can ultimately lead to poor seal quality. In the second step, the vacuum is released, and the part is left in the sealant at atmospheric pressure to allow the sealant to penetrate the orifices and gaps within the part.

[0005] Most commonly, the impregnation liquid is a low-viscosity monomer solution that is easily removed from the outside of the part by spin or similar mechanical means after impregnation, leaving the liquid in the pores and gaps. The low-viscosity monomer solution is then polymerized in situ in downstream processing steps. Low-viscosity monomer materials have been commercially successful, at least in part because they are more easily forced into the pores and gaps of the part. Common monomer materials include, for example, methacrylate monomers with a viscosity typically from about 5 mPa·s to about 65 mPa·s (5-65 centipoise) at 23°C. These are thermosetting materials that polymerize and crosslink into rigid polyacrylate solids. It has been found that, for various reasons, these in-situ polymerized seals tend to fail at the sealing gaps between adjacent metal and plastic parts in certain electronic components, such as cellular phone assemblies, during simulated life durability tests.

[0006] To overcome the shortcomings of in-situ polymerized sealants, polymer impregnation liquids that form sealants after impregnation without polymerization or crosslinking, requiring only drying, can replace monomer solutions from in-situ polymerization. The polymer can be dissolved or dispersed in a solvent (such as water). One disadvantage of polymer / solvent impregnation liquids prepared by adding a certain amount of solvent to achieve a viscosity similar to that of the monomer solution is the energy / time required to dry them. Another potential drawback is ineffective sealing of pores and gaps, caused by insufficient polymer solids in the impregnation liquid leading to shrinkage of the polymer sealant during drying.

[0007] To address this issue, the applicant selected viscous (i.e., sticky) polymer materials with viscosities ranging from approximately 50 Pa·s to up to 3000 mPa·s or greater, containing higher polymer solids and lower solvents, based on the non-Newtonian behavior of the polymers (50-3000 centipoise). Viscous polymer solutions or dispersions have been found to offer improved sealing performance without the need for crosslinking, but this introduces other disadvantages. For example, viscous polymer solutions are less suitable for use in wet vacuum methods because the pressure head over the liquid solution limits how much air can be removed from orifices and gaps (especially for parts located far below the liquid surface), where the positive pressure of the liquid and the vapor pressure of any solvent are unfavorable for vacuuming. Combined with the higher viscosity of the polymer impregnating agent, this results in reduced sealing performance. The problems caused by the liquid pressure head can be mitigated by performing vacuum impregnation in shallow tanks, but commercial production volumes of small parts would require a large number of relatively large-diameter, pressure-rated tanks, which would be costly (especially where stainless steel might be required to resist corrosion from certain polymer impregnating liquids).

[0008] The problems associated with wet vacuum methods can be partially addressed by using dry vacuum methods. With dry vacuum, the tank height does not affect the seal quality because there is no pressure head to overcome; therefore, a smaller number of deeper, smaller-diameter tanks can be used for the same production volume. However, dry vacuum methods also have disadvantages. For example, when the viscous impregnating liquid initially enters the vacuum environment of the evacuated tank, it tends to foam violently. This foam has been observed covering a large area of ​​the vacuum impregnation system, where it dries into a hard coating. Additionally, compared to non-viscous monomers, the viscous impregnating liquid does not drain well from the tank sidewalls at the end of the cycle. Therefore, the foaming impregnating liquid, along with any other impregnating liquid that comes into contact with the tank walls during the process, forms viscous deposits on the tank sidewalls that are difficult to remove after only a few operating cycles. This problem is complicated by the fact that the impregnating liquid is both highly adhesive and resistant to solvent erosion. Therefore, cleaning the inside of the tank almost always requires operator access to the tank, leading to operational complications (such as the need to specify downtime and increased requirements for operator safety).

[0009] Therefore, existing technologies for vacuum impregnation systems can be further improved. Summary of the Invention

[0010] The applicant's invention relates to addressing one or more of the aforementioned disadvantages using a dry vacuum impregnation system and dry impregnation method as disclosed herein.

[0011] According to one aspect of the invention (“Aspect 1”), a vacuum impregnation system is provided, the vacuum impregnation system comprising, substantially comprising, or comprising the following:

[0012] A vacuum container comprising a container and a removable lid, wherein when the lid is on the container, the container and the lid form a substantially closed vacuum chamber;

[0013] A support, which is fixedly or removably supported inside the vacuum chamber and configured to hold one or more articles on the support;

[0014] An inner tank, movably mounted to the container and configured to contain a certain amount of impregnation liquid, the inner tank being vertically movable between a first position and a second position, wherein in the first position the one or more articles are not immersed in the impregnation liquid, and in the second position the one or more articles are at least partially immersed in the impregnation liquid; and

[0015] A vacuum and pressure control system comprising one or more gas control loops that are in fluid communication with the vacuum chamber when the cover is on the container.

[0016] Aspect 2. The vacuum impregnation system as described in aspect 1, wherein the support is removably supported inside the vacuum chamber by at least one attachment.

[0017] Aspect 3. The vacuum impregnation system as described in any of the preceding aspects, wherein the support is fixed to the cover or the container.

[0018] Aspect 4. The vacuum impregnation system as described in any of the preceding aspects, wherein the inner tank is mounted on a shaft that extends through a seal at the bottom of the container.

[0019] Aspect 5. The vacuum impregnation system as described in any of the preceding aspects, wherein the inner tank is removably mounted on the shaft.

[0020] Aspect 6. The vacuum impregnation system as described in any of the preceding aspects, wherein the shaft comprises a linear slider.

[0021] Aspect 7. The vacuum impregnation system as described in any of the preceding aspects, the vacuum impregnation system further comprising an actuator attached to the shaft and configured to move the inner tank between the first position and the second position.

[0022] Aspect 8. The vacuum impregnation system as described in any of the preceding aspects, the vacuum impregnation system further comprising a fluid control loop extending from the inner tank to the impregnation liquid source.

[0023] Aspect 9. The vacuum impregnation system as described in any of the preceding aspects, wherein the fluid control loop includes a flexible channel extending from the inner tank to a fluid port in the container.

[0024] Aspect 10. The vacuum impregnation system as described in any of the preceding aspects, wherein the fluid control loop includes a channel extending through the shaft.

[0025] Aspect 11. The vacuum impregnation system as described in any of the preceding aspects, wherein the vacuum control system comprises one or more of the following: a first gas control loop connected to a vacuum pump, a second gas control loop connected to a pressurized gas source, and an exhaust port that can be selectively opened.

[0026] Aspect 12. The vacuum impregnation system as described in any of the preceding aspects, wherein the inner tank is coated with a non-stick coating.

[0027] Aspect 13. The vacuum impregnation system as described in any of the preceding aspects, wherein the inner tank includes a removable inner liner.

[0028] Aspect 14. The vacuum impregnation system as described in any of the preceding aspects, wherein the liner is a reusable or disposable metal or plastic material liner.

[0029] Aspect 15. The vacuum impregnation system as described in any of the preceding aspects, wherein the inner tank includes a removable inner circumferential band positioned inside the inner tank.

[0030] Aspect 16. The vacuum impregnation system as described in any of the preceding aspects, wherein the belt includes a flat ring pressed against the inner surface of the inner tank and isolates the inner tank from the impregnation liquid at the air / impregnating agent interface.

[0031] According to another aspect of the invention (“Aspect 17”), a method for operating a vacuum impregnation system is provided, the method comprising, substantially comprising, or comprising the following steps:

[0032] (a) Positioning one or more articles in a vacuum chamber under ambient air pressure;

[0033] (b) After step (a), seal the vacuum vessel;

[0034] (c) A certain amount of impregnation liquid is provided in an inner tank located inside the vacuum tank and below the one or more articles;

[0035] (d) After steps (a) and (b), the internal pressure inside the vacuum vessel is reduced to below the ambient air pressure;

[0036] (e) After steps (c) and (d), the inner tank is raised so that the one or more articles are at least partially immersed in the impregnation liquid;

[0037] (f) After step (e), the internal pressure inside the vacuum tank is increased to be higher than the ambient air pressure;

[0038] (g) After step (f), the inner tank is lowered to a position where the one or more articles are not immersed in the impregnation liquid inside the inner tank;

[0039] (h) After step (g), the internal pressure inside the vacuum chamber is reduced to ambient air pressure; and

[0040] (i) After step (h), the vacuum container is opened and the one or more articles are removed from the vacuum container.

[0041] Aspect 18. The method as described in any of the preceding aspects, wherein step (c) is performed before and / or simultaneously with step (a) or step (b).

[0042] Aspect 19. The method as described in any of the preceding aspects, wherein step (c) is performed after step (b).

[0043] Aspect 20. The method as described in any of the preceding aspects, wherein step (d) is performed after step (c) is completed.

[0044] Aspect 21. The method of any of the preceding aspects, wherein the vacuum container comprises a container and a removable lid, and step (a) comprises attaching a support for holding the one or more articles to the container.

[0045] Aspect 22. The method of any of the preceding aspects, wherein the vacuum jar comprises a container and a removable lid, and step (a) comprises attaching a support for holding the one or more articles to the lid.

[0046] Aspect 23. The method of any of the preceding aspects, wherein step (c) comprises pumping the amount of impregnating liquid from the outside of the vacuum tank through a flexible channel and into the inner tank.

[0047] Aspect 24. The method of any of the preceding aspects, wherein the inner can is attached to a shaft extending through the bottom of the vacuum can, and step (e) comprises raising the shaft, and step (g) comprises lowering the shaft.

[0048] Aspect 25. The method of any of the preceding aspects, wherein step (c) comprises pumping the amount of impregnating liquid from the outside of the vacuum tank through a channel extending through the shaft and into the inner tank.

[0049] Aspect 26. The method as described in any of the preceding aspects, wherein the method further comprises (j) after step (i) drying the one or more articles from the vacuum tank in the absence of crosslinking.

[0050] Aspect 27. The method of any of the preceding aspects, wherein step (j) comprises air drying or heating to convert the impregnating agent liquid into a solid.

[0051] In one embodiment, the dry vacuum impregnation system includes a "tank-inside-a-tank" structure, wherein the impregnating polymer is contained in an open inner tank disposed within a pressure-resistant outer tank, the outer tank having a closed lower portion and an upper portion terminating in a sealable opening. The inner tank is positioned below the upper portion of the outer tank, and the part to be impregnated is introduced into the outer tank through the sealable opening. Instead of moving the impregnating polymer between reservoirs, the polymer-containing inner tank is movably disposed within the outer tank, and in use, the inner tank moves upward to surround the part to be coated until the part is immersed in the impregnating polymer. In this way, foaming of the impregnating polymer caused by turbulence of the polymer between the reservoir tank and the vacuum impregnation tank, as well as excessive foaming caused by introducing the polymer into the tank under vacuum, are significantly reduced.

[0052] For an inner tank containing a polymer solution at the bottom of its traverse, the part to be sealed is preferably lowered into the outer tank by a hoisting mechanism or similar means, and the part is suspended above the polymer liquid (typically on a bracket or other support). The top of the outer tank is then closed, sealing the pressure-resistant outer tank, and a vacuum is applied to evacuate air from the pressure-resistant outer tank (including the orifices / gap of the part) of the vacuum impregnation system. The inner tank is then moved upwards, immersing the part in the polymer solution, and the vacuum is released, which helps move the polymer liquid into the gaps and orifices. The outer tank is then pressurized to above atmospheric pressure, which forces additional viscous polymer into the orifices / gap of the part. After a selected time (approximately 30 to 300 seconds), the pressure is released and returned to atmospheric pressure, causing the inner tank to descend, and excess polymer drips from the outer surfaces of the part and the bracket back into the inner tank. The support is raised, and optionally a collection tray for excess polymer is placed below the support. The support is then removed and transported to a cleaning station (where excess polymer on the surface of the part is removed) and then to a drying station, where the polymer is allowed to dry, which converts the viscous polymer liquid into a solid form that optionally has elastomeric properties, thereby sealing the pores and gaps in the article.

[0053] It is noteworthy that when using dry vacuum, the vacuum impregnation reservoir does not require multiple shallow tanks with large footprints to coordinate with the pressure head issues of the wet vacuum method. Therefore, deeper tanks with smaller diameters can be used without adversely affecting the sealing quality. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of an exemplary vacuum impregnation system.

[0055] Figure 2 The diagram illustrates the first operating state. Figure 1 The implementation plan.

[0056] Figure 3 The illustration shows an alternative implementation of an exemplary impregnation system in its first operating state.

[0057] Figure 4 The diagram illustrates the second operating state. Figure 1 The implementation plan.

[0058] Figure 5 The diagram illustrates the third operating state. Figure 1 The implementation plan.

[0059] Figure 6 The illustration shows an exemplary method for operating a vacuum impregnation system.

[0060] In the accompanying drawings, similar reference numerals denote similar features. Detailed Implementation

[0061] The embodiments described herein relate to vacuum impregnation systems and methods for operating vacuum impregnation systems. It will be understood that the embodiments discussed herein are exemplary, and other embodiments may encompass various different aspects or combinations of features described herein.

[0062] Figure 1 The illustration depicts a first exemplary embodiment of a vacuum impregnation system 100. System 100 includes a vacuum canister formed by a container 102 and a lid 104. Container 102 is configured as the lower portion of the vacuum canister and is substantially fluid-tight. Lid 104 is configured as the upper portion of the vacuum canister and is also substantially fluid-tight. Container 102 terminates at its upper end with an upward-facing opening 106, and lid 104 has a similarly shaped downward-facing opening 108. Lid 104 can be secured to container 102 to form a substantially fluid-tight and pressure-tight vacuum chamber 112. One or both openings 106, 108 may be surrounded by or include an O-ring 110 or one or more other seals, which may be disposed on a radially extending flange to facilitate the formation of a substantially fluid-tight closure. As used in this article, “generally fluid seal” means that when all operating channels and openings are closed, no gas or liquid, or only a very small amount of gas or liquid that does not affect the operation of the system, can pass through the structure.

[0063] Container 102 and lid 104 are preferably formed in the shape of a conventional pressure vessel, having cylindrical sidewalls terminating at a dome-shaped, hemispherical, quasi-spherical, or semi-elliptical head. However, container 102 and lid 104 may together form a spherical shape or other shapes. The vacuum vessel can be configured to accommodate the desired operating pressure and vacuum level, and to withstand the desired operating temperature. For example, the vacuum vessel can be rated to operate at an internal pressure ranging from a vacuum of 10 mm Hg to a positive pressure of 20 atmospheres, or more preferably from a vacuum of 20 mm Hg to a positive pressure of 10 atmospheres. The vacuum vessel can also be rated to operate at temperatures from 5°C to 200°C (more preferably from 15°C to 100°C).

[0064] System 100 also includes a bracket 114 (or multiple brackets) configured to be positioned within a vacuum container inside a vacuum chamber 112 (fixed to or removably supported within the vacuum chamber). One or more brackets 114 may be fixed to one or both of a container 102 and a lid 104. Preferably, the bracket 114 is removably supported and / or fixed within the vacuum container. For example, container 102 may include an inner lip 116 extending radially inward from an inner wall surface 118 of the container, and bracket 114 may include an outer lip 120 extending radially outward from bracket 114 to engage the inner lip 116 and hold bracket 114 in a predetermined vertical position within the vacuum chamber 112. Other embodiments may use other mechanisms (such as hooks) to secure bracket 114 to container 102 or lid 104.

[0065] The connection mechanism can be configured for automatically installing and removing the bracket 114 from the vacuum chamber 112. For example, the inner lip 116 and the outer lip 120 can be configured to support the bracket 114 in the vertical direction, but allow some radial and rotational movement to account for inaccuracies in the operation of loading equipment (e.g., cranes or lifting machinery). If desired, mechanisms (such as bolts or clamps) for securing the bracket in position in all directions can be provided to prevent any movement of the bracket 114 when it is in place. Other alternatives and variations will be apparent to those skilled in the art in light of this disclosure.

[0066] In other embodiments, the bracket 114 may be permanently attached to the container 102 or the lid 104. For example, the bracket 114 may be welded in place or secured by fasteners that are not intended to allow removal of the bracket during normal operation and cleaning processes. In this case, removable retainers, supports, baskets, etc., as further described below, may be used to position the parts in the bracket for immersion and, optionally, for transport.

[0067] The support 114 is also configured to hold one or more articles to be vacuum impregnated and to allow the impregnation liquid to contact the articles. For example, the support 114 may comprise a basket or a series of nested baskets supporting the articles from the bottom, or one or more hooks capable of gripping corresponding openings in the articles. The support 114 may also be configured to suspend one or more articles without the support 114 being immersed in the impregnation liquid. For example, each article may be suspended from the support 114 via an intermediate disposable connector (such as a wire or loop made of plastic material). Other alternatives and variations will be apparent to those skilled in the art in light of this disclosure.

[0068] System 100 also includes an inner tank 122, which is generally closed at its lower end to contain a certain amount of impregnating liquid, but has an open top 124, which is sized and shaped to receive a support 114 and / or articles held or suspended from the support. For example, the inner tank 122 may comprise a cylindrical chamber with a diameter slightly smaller than the adjacent portion of the inner wall surface 118 of the container. The inner tank 122 may have a coating of a so-called non-stick material (e.g., polytetrafluoroethylene (PTFE)) and / or may include a removable inner lining 122' (such as a lining of reusable or disposable metal or plastic material), which is intended to facilitate periodic cleaning of the inner tank 122 and allow for the selection of less expensive materials for manufacturing the inner tank 122 and container 102. For example, for surfaces not in direct contact with potentially corrosive polymer impregnating liquids, stainless steel may be replaced with lower-grade steel (such as carbon steel), aluminum, or other suitable metals that do not interfere with the purpose of the invention.

[0069] The inner tank 122 is movably mounted to the container 102 such that it can move vertically between a first position and a second position. In the first position, the article held by the support is not immersed in the impregnation liquid inside the tank, and in the second position, the article is at least partially (preferably completely) immersed in the impregnation liquid. The operation of the inner tank 122 is described in more detail below.

[0070] The inner tank 122 can be movably mounted to the container 102 using any suitable mechanism. In the example shown, the inner tank 122 is mounted on a shaft 126, which extends through a seal 128 at the bottom of the container 102. The shaft 126 and the seal 128 can have any suitable configuration to provide a pressure seal or a pressure-resistant seal. For example, the shaft 126 can comprise a polished stainless steel cylinder extending through an opening penetrating the bottom of the container 102, wherein one or more mechanical seals or gland seals are mounted in the opening and extend radially to contact the shaft 126 to form a sliding seal 128. The seal 128 can include any suitable arrangement of a wiper, sealing lip, compression ring, O-ring, V-ring, wedge, filler material, etc., as known in the field of hydraulic seals. In this case, the shaft 126 is a linear slide that moves axially along the length of the shaft 126 without having to rotate about the axis of the shaft. In other cases, shaft 126 may include a lead screw that engages internally within the bottom of container 102, or have other configurations.

[0071] Actuator 130 is attached to shaft 126 and configured to move inner can 122 between a first (lowered) position and a second (raised) position. In the example shown, actuator 130 includes a hydraulic or pneumatic piston 132 and cylinder 134 assembly, which generates power by pressurizing the cylinder chamber, as is known in the art. In this case, piston 132 is attached to shaft 126 via rigid connector 136. Thus, operating actuator 130 moves piston 132 upward, thereby moving inner can 122 from the first position to the second position. It will be readily understood that this configuration can be modified in various ways. For example, piston 132 can be fixed in place, and cylinder 134 can be connected to shaft 126. As another example, shaft 126 can be shaped to directly mount to the piston in a corresponding hydraulic or pneumatic cylinder. As another example, connector 136 may include one or more mechanisms (such as chains and sprockets, belts and pulleys, gears, linkages, levers, linkages, etc.) to convert the motion of piston 132 into motion of shaft 126. It will also be understood that actuator 130 may alternatively include an electric motor or any other power source. The specific characteristics of actuator 130 and its connection to shaft 126 are not critical to the present invention, and many variations will be understood in light of this disclosure.

[0072] The vacuum impregnation system 100 also includes a fluid control loop 138 configured to supply impregnation liquid to the inner tank 122. The fluid control loop 138 includes any suitable arrangement of valves, channels, and / or pumps to deliver impregnation liquid to (and optionally from) the inner tank 122. For example, the fluid control loop 138 may include a pump 140 and an impregnation liquid valve 142 fluidly connected in series to an impregnation liquid source 144 (e.g., a tank or supply channel).

[0073] The fluid control loop 138 can be connected to the inner tank 122 through various arrangements of fluid channels. Figure 1 In this example, the flexible channel 146 extends from the inner tank 122 to a fluid port 148 through the container 102. The fluid port 148 can be any suitable arrangement of fittings (e.g., pipes with or without threaded connectors), as is known in the field of pressure vessel design. The flexible channel 146 may comprise a flexible hose, etc., and is sized to allow movement of the inner tank 122 between a first position and a second position without impeding movement of the inner tank 122 or obstructing the hose, and is preferably abrasion-resistant to prevent damage from repeated contact with other parts. Steel-braided pressure-rated hoses or other suitable hoses may be used for this purpose, but other alternatives will be apparent to those skilled in the art in light of this disclosure.

[0074] Similarly, Figure 1 As shown, the fluid control loop 138 can alternatively be connected to the inner tank 122 via a channel 150 extending through the shaft 126. This eliminates the need to provide a flexible channel 146 inside the tank environment, but may require a flexible channel 152 to connect the shaft channel 150 to other parts of the fluid control loop 138.

[0075] Implementations using flexible channel 146 or shaft 150 to deliver impregnating liquid to inner tank 122 both provide the option to selectively remove impregnating liquid from inner tank 122 by discharging or pumping in a counter-current direction. This can facilitate returning impregnating liquid to a reservoir for later use, preparing inner tank 122 for cleaning, or provide other benefits.

[0076] However, in other embodiments, the fluid control loop 138 may be configured to deliver the impregnating liquid only to the inner tank 122. For example, the fluid control loop 138 may deliver the impregnating liquid through the open top 124 of the inner tank 122. In one such embodiment, when the inner tank 122 is in a first position, the fluid control loop 138 may include an outlet nozzle attached to the inner wall surface 118 of the container 102 at a location above the open top 124. In this case, the impregnating liquid may be pumped through the nozzle to pour or spray into the inner tank 122, but cannot be removed by backflow. The fluid control loop 138 may also be configured to pour the impregnating liquid into the inner tank 122 through the upper end 106 of the container 102 before attaching the cap 104. Other alternatives and variations will be apparent to those skilled in the art in light of this disclosure.

[0077] It is also envisioned that multiple inner tanks 122 can be used in some embodiments. Such multiple tanks 122 can be used to perform vacuum impregnation on some articles using different impregnation liquids, or to perform vacuum impregnation on smaller batches of articles without filling the entire volume of a single inner tank 122. The multiple inner tanks 122 can be movable together (e.g., attached to the same shaft 126 or provided as discrete sub-parts of a single integrated structure), or they can be movable separately (e.g., mounted on separate shafts and having separate operating systems).

[0078] The inner can 122 can also be removable, such as for cleaning the inner can 122 without personnel entering the container, and to facilitate the use of a replacement can to continue processing parts. The inner can 122 can also be replaced with cans of different sizes, or can be filled to different levels to vacuum impregnate different articles or combinations of articles.

[0079] The inner tank 122 may be fitted with a removable inner circumferential band positioned inside the inner tank approximately at the surface of the impregnating liquid (e.g., the air / impregnating agent interface). The band forms a flat ring pressed against the inner surface of the inner tank 122 and may be, for example, a spring-loaded metal ring. The band isolates the inner tank from the impregnating liquid at the air / impregnating agent interface and can collect polymer deposits generated on the surface of the band during processing, thereby facilitating easy removal of the deposits. This feature may be used in place of or in combination with the liner 122'.

[0080] The vacuum impregnation system 100 also includes a vacuum control system operated to control the gas pressure inside the vacuum chamber 112. For example, the vacuum control system may include a first gas control loop 154, a second gas control loop 156, and a third gas control loop 158. The first gas control loop 154 ​​is used to reduce the gas pressure inside the vacuum chamber 112 to below the ambient pressure outside the vacuum chamber; the second gas control loop 156 is used to increase the gas pressure in the vacuum chamber 112 to above the ambient pressure outside the vacuum chamber; and the third gas control loop 158 is used to equalize the pressure inside the vacuum chamber 112 with the ambient pressure outside the vacuum chamber.

[0081] Gas control loops 154, 156, and 158 can be incorporated into any suitable arrangement of the equipment to provide the desired functionality. For example, in the illustrated embodiment, the first gas control loop 154 ​​may include a first valve 160 connecting the vacuum tank to the vacuum pump 162, the second gas control loop 156 may include a second valve 164 connecting the vacuum tank to the compressor 166, and the third gas control loop may include a third valve 168 connecting the vacuum tank to ambient air. Components of the vacuum control system may also include other devices (such as filters, collectors, meters, etc.). Any automatic or manual control system can be used to operate components of the vacuum control system. Other alternatives and variations will be apparent to those skilled in the art in light of this disclosure.

[0082] The vacuum impregnation system 100 also preferably includes a liquid discharge circuit 170 (such as a liquid discharge valve 172) configured to discharge impregnation liquid, condensate and any other liquid from the bottom of the vacuum tank.

[0083] The selection and use of valves, vacuum pumps, compressors, etc. are well known in the field of vacuum impregnation systems and do not require further discussion in this article.

[0084] Exemplary methods and other implementations for operating the vacuum impregnation system 100 Figures 2 to 6 The illustration shows that an exemplary method begins by loading the article 200 to be sealed onto the holder 114 (step 600), loading the holder 114 onto the container 102 or the lid 104 (step 602), and sealing the vacuum container by securing the lid 104 to the container 102 (step 604). Steps 600 and 602 can be performed in any order (i.e., the article 200 can be loaded onto the holder 114 before or after securing the holder 114 to the container 102 or the lid 104). Figure 2 The article shown is fixed to the bracket 114 before the bracket 114 is fixed to the container 102. Figure 3A bracket 114 is shown as an alternative embodiment for fixing to the cover 104. If the bracket 114 is permanently fixed to the vacuum tank, step 602 is satisfied by default. Figure 4 The bracket 114 fixed to the vacuum tank and the cover 104 fixed to the container 102 to form a sealed vacuum chamber 112 are shown.

[0085] In step 606, the inner tank 122 is filled with impregnation liquid 202 to the desired level. Step 606 can be performed before or after sealing the cap 104 to the container 102. For example, Figure 2 This illustrates that the impregnating liquid 202 is at a low level during loading of the support 114 (or the impregnating liquid 202 may be completely absent), and the impregnating liquid 202 can be maintained at this level until the cap 104 seals to the container 102. In contrast, Figure 3 The illustration shows the impregnation liquid 202 filled to the working level before the cap 104 is sealed to the container 102.

[0086] Step 608 is performed after the cap 104 is sealed to container 102. In step 608, a vacuum is created in vacuum chamber 112, such as by operating the first gas control loop 154 ​​to pump ambient air out of vacuum chamber 112. If necessary, one or more purging steps may be performed before step 608 to help remove gases from the ambient air that may interfere with the process. For example, nitrogen may be pumped into vacuum chamber 112 to displace the ambient air before performing step 608.

[0087] Step 608 is preferably performed after filling the inner canister 122 with the impregnation liquid in step 606. This helps prevent foaming of the impregnation liquid 202, which can occur when the liquid is introduced into a vacuum atmosphere, and provides significant improvements due to easier, safer, and / or less frequent cleaning of the vacuum canister. However, it is contemplated that by introducing the impregnation liquid 202 into the area of ​​the inner canister 122, foaming-related problems can be at least partially isolated to the inner canister 122. In this case, most of all cleaning processes will involve cleaning the inner canister 122, and this process can be facilitated by making the inner canister 122 removable (e.g., by mounting the inner canister 122 to the shaft 126 by nut 174 or one or more other fasteners) or by providing a removable liner 122' in the inner canister 122. Therefore, the implementation may optionally perform the vacuum generation step 608 before or simultaneously with the introduction of the impregnation liquid in step 606.

[0088] Next, in step 610, the inner tank 122 is raised by operating the actuator 130 until the article 200 to be vacuum impregnated is immersed in the impregnation liquid 202. The article 200 may be completely immersed, or only to a desired extent if impregnation of the entire article 200 is not required. During immersion, the impregnation liquid surrounds the article and the holes and gaps to be filled, and can penetrate into such holes and gaps to a certain extent.

[0089] Step 610 is performed after step 608 to make it a dry vacuum impregnation method (i.e., a vacuum is generated before the article 200 is impregnated). This is intended to reduce or eliminate inconsistent impregnation of the article at different locations within the vacuum chamber 112, since the generation of vacuum in the holes does not compete with the hydraulic pressure head generated by the impregnation liquid. This allows the vacuum tank to be relatively large in the vertical direction, resulting in a larger throughput for a given capital investment in the processing equipment.

[0090] When article 200 is immersed, the method proceeds to step 612, in which the second gas control circuit 156 is activated to raise the pressure inside vacuum chamber 112 to above atmospheric pressure. Raising the pressure in the sealed container forces the impregnating liquid into the evacuated holes and gaps to provide an improved seal.

[0091] Next, in step 614, the article 200 is removed from the impregnation liquid by operating the actuator 130 to lower the inner tank 122 until the impregnation liquid is below the lowest article 200 on the support 114. During and after this step, residual impregnation liquid 202 on the article 200 can be discharged from the article 200 to the inner tank 122 for reuse or recycling.

[0092] Finally, in steps 616 and 618, the vacuum chamber 112 is vented by operating the third gas control circuit 158, and the article 200 is removed.

[0093] It will be understood that some or all of the aforementioned method steps can be performed based on various operating parameters. Examples of such parameters include: the magnitude of the vacuum generated in step 608, the magnitude of the pressure generated in step 912, the duration of immersion in step 610, and the waiting time before venting the can in step 616. Furthermore, the temperature of the article 200, the atmosphere in the vacuum chamber 112, and the impregnation liquid 202 are all adjustable. The precise expected values ​​or ranges of such variables can be determined using routine experiments.

[0094] The intended implementation is particularly useful when used with a relatively viscous impregnating liquid, which can be selected to have more or less adhesive properties depending on whether the article is a component that may require maintainable disassembly. Preferably, the impregnating liquid is selected to provide a uniform and consistent seal formation, wherein a durable seal is formed between the sealing material and the various materials constituting the component, including both metals and plastics. The impregnating liquid is also preferably provided as an inert polymer dissolved or dispersed in a solvent (preferably water), which eliminates the need for a separate curing step and requires only the evaporation of the residual carrier or solvent (most preferably water) to complete the seal. Those skilled in the art of polymers will understand that an inert polymer means a polymer that lacks sufficient functional groups to impart a particular chemical reactivity to the polymer. As a non-limiting example, suitable inert polymers may include polyacrylates, polyvinyl alcohol, polyurethanes, polyvinyl acetate, etc. The impregnating liquid may optionally include additives known for formulating adhesives and sealants, such as rheology modifiers, wetting agents, anti-aging agents, stabilizers, biostabilizers, and / or color pigments. Generally, depending on the non-Newtonian behavior of the polymer (50-5000 centipoise) solution, the viscosity of viscous impregnated polymer materials ranges from about 50 Pa·s to up to 5000 mPa·s or greater.

[0095] The implementation scheme can be configured to seal holes and gaps in various articles, including articles having both metal and plastic parts. Exemplary articles include, but are not limited to: telecommunications equipment (e.g., radios, cellular phones, etc.); audio equipment (e.g., headphones, speakers, microphones); and other electronic equipment (e.g., computers, processing units, electronic controllers, wire harnesses, electrical connectors, etc.).

[0096] As previously stated, although the invention has been described and illustrated with reference to specific embodiments herein, the invention is not intended to be limited to the details shown. Rather, various modifications to the details may be made within the scope and within the equivalents of the claims and without departing from the invention.

[0097] In this specification, embodiments have been described in a manner that enables the writing of a clear and concise description; however, it is contemplated and understood that embodiments may be combined or separated in various ways without departing from the invention. For example, it will be understood that all preferred features described herein are applicable to all aspects of the invention described herein.

[0098] While preferred embodiments of the invention have been shown and described herein, it will be understood that such embodiments are provided by way of example only. Many variations, modifications, and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Therefore, the appended claims are intended to cover all such variations falling within the spirit and scope of the invention.

Claims

1. A method for operating a vacuum impregnation system, the method comprising: (a) Positioning one or more articles in a vacuum chamber under ambient air pressure; (b) After step (a), seal the vacuum vessel; (c) A certain amount of impregnation liquid is provided in an inner tank located inside the vacuum tank and below the one or more articles; (d) After steps (a) and (b), the internal pressure inside the vacuum vessel is reduced to below the ambient air pressure; (e) After steps (c) and (d), the inner tank is raised so that the one or more articles are at least partially immersed in the impregnation liquid; (f) After step (e), the internal pressure inside the vacuum tank is increased to be higher than the ambient air pressure; (g) After step (f), the inner tank is lowered to a position where the one or more articles are not immersed in the impregnation liquid inside the inner tank; (h) After step (g), the internal pressure inside the vacuum chamber is reduced to ambient air pressure; and (i) After step (h), the vacuum canister is opened and the one or more articles are removed from the vacuum canister.

2. The method of claim 1, wherein step (c) is performed before and / or simultaneously with step (a) or step (b).

3. The method of claim 1, wherein step (c) is performed after step (b).

4. The method of claim 1, wherein step (d) is performed after step (c) is completed.

5. The method of claim 1, wherein the vacuum jar comprises a container and a removable lid, and step (a) comprises attaching a support for holding the one or more articles to the container.

6. The method of claim 1, wherein the vacuum jar comprises a container and a removable lid, and step (a) comprises attaching a support for holding the one or more articles to the lid.

7. The method of claim 1, wherein step (c) comprises pumping the amount of impregnation liquid from the outside of the vacuum tank through a flexible channel and into the inner tank.

8. The method of claim 1, wherein the inner can is attached to a shaft extending through a seal at the bottom of the vacuum can, and step (e) comprises raising the shaft, and step (g) comprises lowering the shaft.

9. The method of claim 8, wherein step (c) comprises pumping the amount of impregnating liquid from the outside of the vacuum tank through a channel extending through the shaft and into the inner tank.

10. The method of claim 1, further comprising (j) after step (i) drying the one or more articles from the vacuum tank in the absence of crosslinking.

11. The method of claim 10, wherein step (j) comprises air drying or heating to convert the impregnating liquid into a solid.

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