System and method for vacuum impregnation

Abstract

A vacuum impregnation system and process for applying a vacuum to a part, immersing the part in a polymer impregnation liquid, applying positive pressure to the part to introduce the polymer impregnation liquid into the part's pores, relieving the pressure to atmospheric pressure, and preferably solidifying the polymer impregnation liquid without an active polymerization step.

Description

Technology Field

[0001] The present invention generally relates to the field of a vacuum impregnation system and process in which a vacuum is applied to a part, the part is immersed in an impregnation liquid, positive pressure is applied to the part to introduce the impregnation liquid into the pores of the part, and the impregnation liquid is solidified therein. Background Technology

[0002] Vacuum impregnation systems are used to seal pores and small gaps in articles, such as single parts or assembled parts. Such sealing is useful for helping to reduce or prevent, for example, the entry of water, oil, soil, and other contaminants into the parts or assemblies, and for preventing corrosion of the articles. Articles may include cast metals and other materials, including combinations of metal and plastic materials. Generally, vacuum impregnation is performed by applying a vacuum to the article, bringing the article into contact with an impregnation liquid, and then applying positive pressure to help move the impregnation liquid into the pores and gaps. Vacuum impregnation processes can be classified into two groups: dry vacuum and wet vacuum.

[0003] Dry vacuum impregnation means that a part is placed in a sealed chamber containing a gaseous environment, such as ambient air, when a vacuum is applied to remove the gaseous phase from the chamber, including pores and gaps within the article; subsequently, while the vacuum is maintained, a sealant is transferred from a reservoir into the sealed chamber; and when the vacuum is released, the sealant is drawn into the pores, and the unused sealant is returned to the reservoir. Dry vacuum impregnation may include the step of applying a positive pressure, generally about 4-7 bar (400-700 kPa), after the vacuum is released so that the sealant can penetrate into the pores, and the step of maintaining the pressure for a selected time.

[0004] Wet vacuum means that a part is immersed in an impregnation liquid in a vacuum chamber and then maintained until a vacuum is applied and all air is removed from the container and the sealant. Wet vacuum presents a challenge in overcoming the hydraulic head pressure of the sealant, which reduces the negative pressure on the pores and gaps within the vacuum chamber. This has the disadvantage of trapping a finite amount of air within the pores, which can ultimately lead to poorer sealing quality. In the second step, the vacuum is released, and the article is left in the sealant at atmospheric pressure to allow the sealant to penetrate into the pores and gaps within the article.

[0005] Most commonly, the impregnation liquid is a low-viscosity monomer solution that, after impregnating the part, is easily removed from the outside of the part by rotation or similar mechanical means, while the liquid remains within the pores and gaps. Subsequently, in a subsequent processing step, the low-viscosity monomer solution is in-situ ( on site ) are polymerized. Low-viscosity monomer materials have been at least partially commercially successful because they are easier to push into the pores and gaps of parts. Conventional monomer materials include, for example, methacrylate monomers having a viscosity typically of about 5 mPa·s to about 65 mPa·s (5-65 centipoise) at 23°C. These are thermosetting materials that are polymerized and crosslinked into hard polyacrylate solids. For various reasons, these in-situ polymerized seals have been found to tend to fail in the seal gap between adjacent metal and plastic parts on certain electronic device assemblies, such as mobile phone assemblies, in simulated life endurance tests.

[0006] In an effort to overcome the drawbacks of in-situ polymerized seals, polymer impregnation liquids that require only drying and do not require polymerization or crosslinking after impregnation to form a seal can replace monomer solutions that are polymerized in-situ. The polymer can be dissolved or dispersed in a solvent, such as water. One disadvantage of polymer / solvent impregnation liquids prepared to have a viscosity similar to that of a monomer solution by adding a certain amount of solvent is the energy / time required to dry them. Another possible disadvantage is the ineffective sealing of pores and gaps due to shrinkage of the polymer sealant upon drying caused by a lack of sufficient polymer solids in the impregnation liquid.

[0007] To address these issues, the applicant selected a concentrated (i.e., viscous) polymer material containing higher polymer solids and less solvent, having a viscosity in the range of about 50 Pa·s to 3000 mPa·s (50-3000 centipoise) or higher, depending on the non-Newtonian behavior of the polymer. Concentrated polymer solutions or dispersions have been found to provide improved sealing performance and do not require crosslinking, but they result in other disadvantages. For example, concentrated polymer solutions are less suitable for use in wet vacuum processes because the hydrostatic pressure on the liquid solution limits the extent to which air can be removed from pores and gaps, particularly for parts located below the liquid surface where the positive pressure of the liquid and the vapor pressure of any solvent act against the vacuum being drawn in. Combined with the higher viscosity of the polymer impregnating agent, this results in reduced sealing performance. While problems caused by liquid hydrostatic pressure can be reduced by performing the vacuum impregnation process in shallow tanks, the commercial production of small parts will require a number of relatively large-diameter rated pressure tanks, which will incur enormous costs, especially if stainless steel is required to resist corrosion caused by specific polymer impregnation liquids.

[0008] The problems associated with using a wet vacuum process can be resolved to some extent by using a dry vacuum process. With a dry vacuum, since there is no hydrostatic pressure to overcome, the vessel height does not affect the sealing quality; consequently, fewer, deeper, small-diameter tanks can be used for the same production volume. However, the dry vacuum process also has disadvantages. For example, when the concentrated impregnation liquid first enters the vacuum environment of the exhaust tank, vigorous foaming tends to occur. This foam has been observed to cover a large area of ​​the vacuum impregnation system, where it dries into a hard coating. Furthermore, unlike dilute monomers, the concentrated impregnation liquid does not drain well from the sidewalls of the tank at the end of the cycle. Consequently, the foamed impregnation liquid and any other impregnation liquid in contact with the tank walls during the process form thick, difficult-to-remove deposits on the sidewalls of the tank after only a few operating cycles. This problem is exacerbated by the fact that the impregnation liquid is highly adhesive and also resistant to solvent attack. Therefore, cleaning the interior of a tank will almost certainly require a worker to enter the vessel, which results in operational complexity such as the need to schedule downtime and increased requirements to ensure worker safety.

[0009] Therefore, the technical status of the vacuum impregnation system can be further improved.

[0010] The present applicant's invention relates to solving one or more of the disadvantages described above by using a dry vacuum impregnation system and a dry impregnation process as disclosed herein.

[0011] According to one aspect of the present invention ("Aspect 1"),

[0012] A vacuum tank comprising a receptacle and a removable lid, wherein when the lid is on the receptacle, the receptacle and the lid generally form a sealed vacuum chamber;

[0013] A rack fixed or removablely supported inside a vacuum chamber and configured to hold one or more items thereon;

[0014] An inner tank movably mounted on a receptacle and configured to hold a certain amount of impregnation liquid therein, wherein the inner tank is vertically movable between a first position in which one or more articles are not immersed in the impregnation liquid and a second position in which 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 circuits in fluid communication with a vacuum chamber when the lid is on the receptacle

[0016] A vacuum impregnation system comprising, essentially composed of, or composed of is provided.

[0017] A side 2. A vacuum impregnation system according to side 1, wherein the rack is removablely supported inside a vacuum chamber by at least one attachment.

[0018] Aspect 3. A vacuum impregnation system in which, in any one of the above aspects, the rack is fixed to a lid or receptacle.

[0019] A side 4. A vacuum impregnation system in which, in any one of the above sides, the internal tank is mounted on a shaft extending through a seal portion at the bottom of the receptacle.

[0020] A side 5. A vacuum impregnation system in which, in any one of the above sides, an internal tank is removablely mounted on a shaft.

[0021] Aspect 6. A vacuum impregnation system in which, in any one of the above aspects, the shaft includes a linear slider.

[0022] A vacuum impregnation system comprising, in any one of the above sides, an actuator attached to a shaft and configured to move an internal tank between a first position and a second position.

[0023] A side 8. A vacuum impregnation system that, in any one of the above sides, further comprises a fluid control circuit extending from an internal tank to a source of impregnation liquid.

[0024] Aspect 9. A vacuum impregnation system wherein, in any one of the above aspects, the fluid control circuit comprises a flexible passage extending from an inner tank to a fluid port within a receptacle.

[0025] A side 10. A vacuum impregnation system in which, in any one of the above sides, a fluid control circuit includes a passage extending through a shaft.

[0026] A vacuum impregnation system, wherein in any one of the above aspects, the vacuum control system comprises one or more of a first gas control circuit communicating with a vacuum pump, a second gas control circuit communicating with a source of pressurized gas, and a vent that can be optionally opened.

[0027] A side 12. A vacuum impregnation system in which, in any one of the above sides, the inner tank is coated with a non-stick coating.

[0028] Aspect 13. A vacuum impregnation system in which, in any one of the above aspects, the inner tank comprises a removable inner liner.

[0029] Aspect 14. A vacuum impregnation system in any one of the above aspects, wherein the liner is a liner of a metal or plastic material that is reusable or disposable.

[0030] A side 15. A vacuum impregnation system in which, in any one of the above sides, the inner tank comprises a removable inner perimeter band located within the inner tank.

[0031] A side 16. A vacuum impregnation system in which, in any one of the above sides, a band comprises a flat ring that is pressed against the inner surface of an inner tank and isolates the inner tank from the impregnation liquid at the air / impregnation agent interface.

[0032] According to another aspect of the present invention (“Aspect 17”), a method of operating a vacuum impregnation system comprising, essentially consisting of, or consisting of the following steps is provided:

[0033] (a) A step of placing one or more articles inside a vacuum tank at ambient air pressure;

[0034] (b) After step (a), a step of sealing the vacuum tank;

[0035] (c) a step of providing a certain amount of impregnation liquid into an inner tank located inside a vacuum tank and also located below one or more articles;

[0036] (d) After steps (a) and (b), a step of reducing the internal pressure inside the vacuum tank to below the ambient air pressure;

[0037] (e) After steps (c) and (d), a step of raising the inner tank so that one or more articles are at least partially immersed in the impregnation liquid;

[0038] (f) After step (e), a step of increasing the internal pressure inside the vacuum tank to exceed the ambient air pressure;

[0039] (g) After step (f), lowering the inner tank to a position where one or more articles are not immersed in the impregnation liquid inside the inner tank;

[0040] (h) After step (g), a step of reducing the internal pressure inside the vacuum tank to the ambient air pressure; and

[0041] (i) After step (h), a step of opening the vacuum tank and removing one or more items from the vacuum tank.

[0042] Aspect 18. A method in which, in any one of the above aspects, step (c) is performed before and / or simultaneously with step (a) or step (b).

[0043] Aspect 19. A method in which, in any one of the above aspects, step (c) is performed after step (b).

[0044] Aspect 20. A method in which, in any one of the above aspects, step (d) is performed after step (c) is completed.

[0045] Aspect 21. A method wherein, in any one of the above aspects, the vacuum tank comprises a receptacle and a removable lid, and step (a) comprises attaching a rack holding one or more articles to the receptacle.

[0046] Aspect 22. A method wherein, in any one of the above aspects, the vacuum tank comprises a receptacle and a removable lid, and step (a) comprises attaching a rack holding one or more articles to the lid.

[0047] Aspect 23. A method in which, in any one of the above aspects, step (c) comprises pumping a certain amount of impregnating liquid from outside the vacuum tank into the inner tank through a flexible passage.

[0048] Aspect 24. A method in which, in any one of the above aspects, an inner tank is attached to a shaft extending through a seal at the bottom of a vacuum tank, step (e) includes raising the shaft, and step (g) includes lowering the shaft.

[0049] Aspect 25. A method in which, in any one of the above aspects, step (c) comprises pumping a certain amount of impregnating liquid from outside the vacuum tank into an inner tank through a passage extending through a shaft.

[0050] Aspect 26. A method comprising, in any one of the above aspects, further comprising, after step (i), a step of drying one or more articles from a vacuum tank (j) without a crosslinking step.

[0051] Aspect 27. In any one of the above aspects, the method wherein step (j) comprises air drying or heating to convert the impregnating agent liquid into a solid.

[0052] In one embodiment, a dry vacuum impregnation system comprises a tank-in-tank structure in which an impregnation polymer is contained in an upper-open inner tank disposed within a pressure-resistant outer tank having a closed bottom and a top terminated at a sealable opening. The inner tank is positioned below the top of the outer tank, and a part to be impregnated is introduced therein through the sealable opening. Instead of moving the impregnation polymer from one tank to another, the inner tank containing the polymer is movably positioned within the outer tank, and in use, the inner tank moves upward to surround the part to be coated until the part is submerged in the impregnation polymer. In this way, foaming of the impregnation polymer caused by the turbulence of the polymer between the reservoir tank and the vacuum impregnation tank, and excessive foaming caused by introducing the polymer into the tank under vacuum, are significantly reduced.

[0053] With the inner tank containing the polymer solution in the lower part of the zone, the part to be sealed is preferably lowered into the outer tank by a hoist or the like, and the part is suspended above the polymer liquid, typically on a rack or other support. Then, the top of the outer tank is closed, the pressure-resistant outer tank is sealed, and a vacuum is applied to exhaust air from within the pressure-resistant outer tank of the vacuum impregnation system, including the pores / gaps of the part. Then, the inner tank is moved upward to immerse the part in the polymer solution, and the vacuum is released to move the polymer liquid into the gaps and pores. Then, the outer tank is pressurized to above atmospheric pressure, which pushes additional concentrated polymer into the pores / gaps of the part. After a selected time, about 30 to 300 seconds, the pressure is released and returned to atmospheric pressure, and the inner tank is lowered, so that the excess polymer drips from the outer surface of the part and re-enters the inner tank. The rack is raised, a catch tray for optional excess polymer is placed under the rack, and then the rack is removed and moved to a cleaning station where excess polymer on the surface of the part is removed, and from there to a drying station where the polymer is dried, which seals the pores and gaps of the article by converting the viscous polymer liquid into a solid form having optional elastomer properties.

[0054] In particular, when dry vacuum is used, the vacuum impregnation vessel does not need to have the large space occupied by multiple shallow tanks to address the hydrostatic pressure problem of the wet vacuum process. Therefore, deeper tanks with smaller diameters can be used without negatively affecting the sealing quality. Brief explanation of the drawing

[0055] Figure 1 is a schematic diagram of an exemplary vacuum impregnation system. FIG. 2 illustrates an embodiment of FIG. 1 in a first operating state. FIG. 3 illustrates an alternative embodiment of an exemplary impregnation system in a first operating state. FIG. 4 illustrates an embodiment of FIG. 1 in a second operating state. FIG. 5 illustrates an embodiment of FIG. 1 in a third operating state. Figure 6 illustrates an exemplary method for operating a vacuum impregnation system. In drawings, the same reference number indicates the same feature. Specific details for implementing the invention

[0056] The embodiments described herein relate to a vacuum impregnation system and a method of operating the vacuum impregnation system. The embodiments discussed herein are exemplary, and it should be understood that other embodiments may encompass combinations of various different aspects or features described herein.

[0057] FIG. 1 illustrates a first exemplary embodiment of a vacuum impregnation system (100). The system (100) comprises a vacuum tank formed by a receptacle (102) and a lid (104). The receptacle (102) is configured as the lower part of the vacuum tank and is generally fluid-sealed. The lid (104) is configured as the upper part of the vacuum tank and is also generally fluid-sealed. The receptacle (102) terminates at an upward opening (106) at its upper end, and the lid (104) has a similar-shaped downward opening (108). The lid (104) can be fixed to the receptacle (102) to form a vacuum chamber (112) that is generally fluid and pressure-sealed. One or both openings (106, 108) may be surrounded by or include an O-ring (110) or other seal(s), which may be provided on a radially extending flange to assist in the formation of a generally fluid-sealed enclosure. As used herein, “generally fluid-sealed” means that when all operating passages and openings are closed, no gas or liquid can pass through the structure, or only a very small amount of gas or liquid that does not affect the operation of the system can pass through the structure.

[0058] The receptacle (102) and lid (104) may preferably be formed in the shape of a conventional pressure vessel having cylindrical sidewalls that terminate at a dome-shaped, hemispherical, conical, or semi-elliptical head. However, the receptacle (102) and lid (104) may form a spherical shape as a whole, or other shapes. The vacuum tank may be configured to accommodate the desired operating pressure and vacuum as well as withstand the expected operating temperature. For example, the vacuum tank may be rated to operate at an internal pressure in the range of a vacuum of 10 mm Hg to a positive pressure of 20 atmospheres, or more preferably at a vacuum of 20 mm Hg to a positive pressure of 10 atmospheres. The vacuum tank may also be rated to operate at 5°C to 200°C, more preferably at 15°C to 100°C.

[0059] The system (100) also includes a rack (114) (or a plurality of racks) configured to be fixed within a vacuum chamber or removablely supported within a vacuum chamber and positioned within a vacuum tank within a vacuum chamber (112). The rack (114) or racks may be fixed to one or both of the receptacle (102) and the lid (104). The rack (114) is preferably removablely supported and / or fixed within a vacuum tank. For example, the receptacle (102) may include an inner lip (116) extending radially inward from the inner wall surface (118) of the receptacle, and to engage with the inner lip (116) and maintain the rack (114) in a predetermined vertical position within the vacuum chamber (112), the rack (114) may include an outer lip (120) extending radially outward from the rack (114). In other embodiments, other mechanisms such as hooks may be used to secure the rack (114) to the receptacle (102) or lid (104).

[0060] A connecting mechanism may be configured for the automated installation and removal of the rack (114) from the vacuum chamber (112). For example, the inner and outer ribs (116, 120) support the rack (114) in a vertical direction, but may be configured to allow some degree of radial and rotational movement to account for inaccuracies in the operation of loading equipment (e.g., a crane or ceiling hoist). If desired, a mechanism, such as a bolt or clamp, may be provided to fix the position of the rack in all directions to prevent any movement of the rack (114) when the rack (114) is in place. Other alternatives and variations will be apparent to a person skilled in the art in light of the present disclosure.

[0061] In another embodiment, the rack (114) may be permanently attached to the receptacle (102) or the lid (104). For example, the rack (114) may be welded in place or secured by fasteners that are not intended to allow removal of the rack during normal operation and cleaning procedures. In this case, as further described below, a removable holder, support, basket, etc., for impregnation and optional movement may be used to position parts on the rack.

[0062] The rack (114) is also configured to hold one or more articles to be vacuum impregnated and to allow the impregnation liquid to come into contact with the articles. For example, the rack (114) may include a mesh basket or a series of stacked mesh baskets that support the articles from below, or one or more hooks that may hold corresponding openings within the articles. The rack (114) may also be configured to suspend articles or articles without the rack (114) being immersed in the impregnation liquid. For example, each article may be suspended from the rack (114) by an intermediate disposable connector, such as a strand or loop of plastic material. Other alternatives and variations will be apparent to a person skilled in the art in light of the present disclosure.

[0063] The system (100) further comprises an inner tank (122), which is closed at the bottom to hold a certain amount of impregnating liquid, but has an open top (124) that is dimensioned and shaped to accommodate a rack (114) and / or an article held by or suspended from the rack. 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 receptacle. The inner tank (122) may have a coating of a so-called non-stick material, e.g., polytetrafluoroethylene (PTFE), and / or may comprise a removable inner liner (122'), such as a liner of a metal or plastic material that is reusable or disposable, which is expected to facilitate periodic cleaning of the inner tank (122) and enable the selection of less expensive materials for the fabrication of the inner tank (122) and the receptacle (102). For example, for surfaces that do not come into direct contact with a polymer-impregnated liquid that may be corrosive, stainless steel may be replaced with a lower grade steel, such as carbon steel, aluminum, or other suitable metal, which does not interfere with the purpose of the present invention.

[0064] The inner tank (122) is movably mounted on the receptacle (102) so as to be able to move vertically between a first position in which the article held by the rack is not immersed in the impregnation liquid in the tank and a second position in which 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.

[0065] The inner tank (122) may be movably mounted to the receptacle (102) using any suitable mechanism. In the illustrated example, the inner tank (122) is mounted on a shaft (126) that extends through a seal (128) at the bottom of the receptacle (102). The shaft (126) and the seal (128) may have any suitable configuration to provide a pressure-sealed or pressure-resistant seal. For example, the shaft (126) may comprise a polished stainless steel cylinder that extends through an opening through the bottom of the receptacle (102), wherein one or more mechanical or gland seals are mounted within the opening and extend radially to contact the shaft (126) to form a sliding seal (128). The sealing portion (128) may include any suitable arrangement such as a wiper, sealing lip, compression ring, O-ring, V-ring, wedge, packing material, etc., as is known in the technical field of hydraulic sealing. In this case, the shaft (126) does not necessarily need to rotate about the axis of the shaft and is a linear slider that moves axially along the length of the shaft (126). In other cases, the shaft (126) may include a lead screw that engages with an internal thread within the lower part of the receptacle (102) or may have other configurations.

[0066] The actuator (130) is attached to the shaft (126) and configured to move the inner tank (122) between a first (lower) position and a second (up) position. In the illustrated example, the actuator (130) comprises a hydraulic or pneumatic piston (132) and cylinder (134) assembly, which generates thrust by pressurizing the cylinder chamber as is known in the art. In this case, the piston (132) is attached to the shaft (126) by a rigid connector (136). Thus, the operation of the actuator (130) moves the inner tank (122) from the first position to the second position by moving the piston (132) upward. It will be readily understood that this configuration can be modified in various ways. For example, the piston (132) may be fixed in place and the cylinder (134) may be connected to the shaft (126). As another example, the shaft (126) may be shaped as a piston that fits directly into a corresponding hydraulic or pneumatic cylinder. As another example, the connector (136) may include one or more mechanisms, such as a chain and sprocket, a belt and pulley, a gear, a transmission, a lever, a linkage, etc., to convert the motion of the piston (132) into the motion of the shaft (126). It will also be understood that the actuator (130) may alternatively include an electric motor or any other source of power motion. The specific nature of the actuator (130) and its connection to the shaft (126) is not important to the present invention, and many variations will be understood in light of the present disclosure.

[0067] The vacuum impregnation system (100) also includes a fluid control circuit (138) configured to provide an impregnation liquid to an internal tank (122). The fluid control circuit (138) includes any suitable arrangement of valves, passages, and / or pumps for transporting the impregnation liquid to (and optionally from) the internal tank (122). For example, the fluid control circuit (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 passage).

[0068] The fluid control circuit (138) may be connected to the inner tank (122) by various arrangements of fluid passages. In the example of FIG. 1, the flexible passage (146) extends from the inner tank (122) to a fluid port (148) passing through the receptacle (102). The fluid port (148) may be any suitable arrangement of tubular fittings (e.g., pipes with or without spiral connectors) as known in the art of pressure vessel design. The flexible passage (146) may include a flexible hose, etc., and is dimensioned so that the inner tank (122) can move between a first and second position without hindering the movement of the inner tank (122) or blocking the hose, and is also preferably wear-resistant to prevent damage from repeated contact with other parts. While steel-braided pressure-rated hoses or other suitable hoses may be used for this purpose, other alternatives will be apparent to those skilled in the art in light of the present disclosure.

[0069] Additionally, as illustrated in FIG. 1, the fluid control circuit (138) may alternatively be connected to the internal tank (122) by a passage (150) extending through the shaft (126). This eliminates the need to provide a flexible passage (146) within the tank environment, but may require a flexible passage (152) to connect the shaft passage (150) to other parts of the fluid control circuit (138).

[0070] Both embodiments using a flexible passage (146) or shaft (150) to transfer the impregnation liquid to the inner tank (122) provide an option to selectively remove the impregnation liquid from the inner tank (122) by draining or pumping it in a reverse direction. This may be advantageous for returning the impregnation liquid to a reservoir for future use, preparing the inner tank (122) for cleaning, or providing other benefits.

[0071] Nevertheless, in another embodiment, the fluid control circuit (138) may be configured to deliver the impregnation liquid only to the inner tank (122). For example, the fluid control circuit (138) may deliver the impregnation liquid through the open top (124) of the inner tank (122). In one such embodiment, the fluid control circuit (138) may include an outlet nozzle attached to the inner wall surface (118) of the receptacle (102) at a position above the open top (124) when the inner tank (122) is in the first position. In this case, the impregnation liquid may be pumped through the nozzle and poured or sprayed into the inner tank (122), but cannot be removed by backflow. The fluid control circuit (138) may also be configured to pour the impregnation liquid into the inner tank (122) through the top part (106) of the receptacle (102) before the lid (104) is attached. Other alternatives and variations will be apparent to those skilled in the art in light of the present disclosure.

[0072] In addition, in some embodiments, it is considered that a plurality of internal tanks (122) may be used. These plurality of tanks (122) may be useful for performing vacuum impregnation of several articles using different impregnation liquids, or for performing vacuum impregnation of a smaller batch of articles without the need to fill the entire volume of a single internal tank (122). The plurality of internal tanks (122) may be movable together (e.g., attached to the same shaft (126) or provided as separate subdivisions of a single integrated structure), or may be movable individually (e.g., mounted on separate shafts and having separate operating systems).

[0073] Additionally, the inner tank (122) may be removable, for example, for cleaning without the entry of personnel into the receptacle, and to facilitate continuous processing of parts using a replacement tank. The inner tank (122) may also be replaceable with a tank having different dimensions or filled to different levels in order to vacuum impregnate different articles or combinations of articles.

[0074] The inner tank (122) may be equipped with a removable inner circumference band located within the inner tank, around the surface of the impregnation liquid, for example, the air / impregnation agent interface. The band forms a flat ring that is pressed against the inner surface of the inner tank (122) and may also be, for example, a spring-loaded metal ring. The band isolates the inner tank from the impregnation liquid at the air / impregnation agent interface and facilitates easy removal of deposits by collecting polymer deposits generated on the surface of the band during processing. These features may be used instead of or in combination with the liner (122').

[0075] 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 circuit (154) used to reduce the gas pressure inside the vacuum chamber (112) to less than the ambient pressure outside the vacuum tank, a second gas control circuit (156) used to increase the gas pressure inside the vacuum chamber (112) to more than the ambient pressure outside the vacuum tank, and a third gas control circuit (158) used to make the pressure inside the vacuum chamber (112) equal to the ambient pressure outside the vacuum tank.

[0076] The gas control circuits (154, 156, 158) may include any suitable arrangement of equipment to provide the desired function. For example, in the illustrated embodiment, the first gas control circuit (154) may include a first valve (160) connecting the vacuum tank to a vacuum pump (162), the second gas control circuit (156) may include a second valve (164) connecting the vacuum tank to a compressor (166), and the third gas control circuit 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, liquid traps, gauges, etc. Any automated or manual-operated control system may be used to operate the components of the vacuum control system. Other alternatives and variations will be apparent to those skilled in the art in light of the present disclosure.

[0077] The vacuum impregnation system (100) also preferably includes a liquid discharge circuit (170) and a liquid discharge valve (172) configured to discharge, for example, impregnation liquid, condensate, and any other liquid from the bottom of the vacuum tank.

[0078] The selection and use of valves, vacuum pumps, compressors, etc., are known in the relevant technical field of vacuum impregnation systems and do not require further detailed discussion herein.

[0079] An exemplary method for operating a vacuum impregnation system (100) and other embodiments is illustrated in FIGS. 2 through 6. An exemplary process begins by loading an article (200) to be sealed onto a rack (114) (step (600)), loading the rack (114) onto a receptacle (102) or a lid (104) (step (602)), and also sealing the vacuum tank by securing the lid (104) to the receptacle (102) (step (604)). Steps (600) and (602) may be performed in any order (i.e., the article (200) may be loaded onto the rack (114) before or after the rack (114) is secured to the receptacle (102) or the lid (104). FIG. 2 illustrates the article being secured to the rack (114) before the rack (114) is secured to the receptacle (102). FIG. 3 illustrates an alternative embodiment in which the rack (114) is fixed to the lid (104). When the rack (114) is permanently attached to the vacuum tank, step (602) is satisfied with the initial setup. FIG. 4 illustrates the rack (114) being fixed to the vacuum tank and the lid (104) being fixed to the receptacle (102) to form a sealed vacuum chamber (112).

[0080] In step (606), the inner tank (122) is filled with impregnation liquid (202) to a desired level. Step (606) may be performed before or after the lid (104) is sealed to the receptacle (102). For example, FIG. 2 illustrates a low level of impregnation liquid (202) during loading of the rack (114) (or may be completely absent), and the impregnation liquid (202) may be maintained at this level until the lid (104) is sealed to the receptacle (102). In contrast, FIG. 3 illustrates the impregnation liquid (202) filled to a working level before the lid (104) is sealed to the receptacle (102).

[0081] Step (608) is performed after the lid (104) is sealed to the receptacle (102). In step (608), a vacuum is created in the vacuum chamber (112) by, for example, operating the first gas control circuit (154) to pump ambient air out of the vacuum chamber (112). If desired, one or more purge steps may be performed before step (608) to help remove gases in the ambient air that may interfere with the process. For example, nitrogen may be pumped into the vacuum chamber (112) to replace the ambient air before performing step (608).

[0082] Step (608) is preferably performed after the inner tank (122) has been filled with the impregnation liquid in step (606). This helps prevent foaming of the impregnation liquid (20) that may occur when the liquid is introduced into a vacuum environment, and also provides a significant improvement by facilitating easier / easier, safer / safer, or less frequent cleaning of the vacuum tank. However, it is considered that by introducing the impregnation liquid (202) into the boundaries of the inner tank (122), the problem associated with foaming can be isolated to at least some extent to the inner tank (122). In this case, most of the cleaning process is to clean the inner tank (122), and this process can be facilitated by making the inner tank (122) removable (e.g., by mounting it to the shaft (126) by a nut (174) or other fastener(s), or by providing a removable liner (122') to the inner tank (122). Accordingly, the embodiment may optionally perform the vacuum generation step (608) before or simultaneously with introducing the impregnation liquid in step (606).

[0083] 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, if impregnation of the entire article (200) is not required, may be immersed only to the desired extent. When immersed, the impregnation liquid surrounds the article and the pores and gaps to be filled, and may enter these pores and gaps to some extent.

[0084] Performing step (610) after step (608) makes this a dry vacuum impregnation process (i.e., a vacuum is created before immersing the article (200)). This is expected to reduce or eliminate inconsistent impregnation of the article at different locations within the vacuum chamber (112) because the creation of a vacuum in the pores does not compete with the hydrostatic pressure generated by the immersion liquid. This allows the vacuum tank to be made relatively large in the vertical direction, resulting in a larger processing volume for a given capital investment in the processing equipment.

[0085] With the article (200) immersed, the process moves to step (612), where the second gas control circuit (156) is operated to raise the internal pressure of the vacuum chamber (112) above atmospheric pressure. Raising the pressure within the closed receptacle pushes the impregnating liquid into the exhausted pores and gaps, providing an improved seal.

[0086] 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 rack (114). During and after this step, any remaining impregnation liquid (202) on the article (200) can be drained from the article (200) into the inner tank (122) and reused or recirculated.

[0087] Finally, in steps (616) and (618), the vacuum chamber (112) is exhausted by operating the third gas control circuit (158), and the article (200) is removed.

[0088] It will be understood that some or all of the above process steps may be performed according to various operating parameters. Examples of such parameters include: the magnitude of the vacuum created in step (608), the magnitude of the pressure generated in step (612), the immersion period in step (610), the waiting time before exhausting the tank in step (616), etc. Additionally, the temperature of the article (200), the atmosphere within the vacuum chamber (112), and the impregnation liquid (202) may be adjusted. Precise target values ​​or ranges for these variables may be determined through routine experimentation.

[0089] The embodiment is expected to be particularly useful when used with a relatively viscous impregnation liquid, and the impregnation liquid may be selected to have more or less adhesive properties depending on whether the article is an assembly that may require disassembly for maintenance. Preferably, the impregnation liquid is selected to provide a uniform and consistent seal formation, with a durable seal being formed between the sealing material and the very diverse materials constituting the assembly, including both metals and plastics. The impregnation 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. An inert polymer will be understood by those skilled in the art of polymers to mean a polymer lacking sufficient functional groups to impart specific chemical reactivity to the polymer. Suitable inert polymers may include, as non-limiting examples, polyacrylates, polyvinyl alcohols, polyurethanes, polyvinyl acetates, etc. The impregnation liquid may optionally include additives known to be used in the formulation of adhesives and sealants, such as rheology aids, wetting agents, anti-aging agents, stabilizers, bioinhibitors, and / or coloring pigments. Generally, the thickened impregnation polymer material has a viscosity in the range of about 50 Pa.s to 5000 mPa.s or more, depending on the non-Newtonian behavior of the polymer (50-5000 centipoise) solution.

[0090] Embodiments may be configured to seal pores 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., radio, mobile phone, etc.); audio equipment (e.g., headphones, speakers, microphones); and other electronic equipment, such as computers, processing units, electronic controllers, wiring harnesses, electrical connectors, etc.

[0091] As previously mentioned, although the present invention has been illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details presented. Rather, various modifications to the details may be made within the scope and range of the claims equivalents and without departing from the invention.

[0092] In this specification, embodiments are described in a manner that allows for a clear and concise specification; however, it is intended 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.

[0093] Although preferred embodiments of the present invention have been presented and described herein, it should be understood that such embodiments are provided merely as examples. A number of variations, changes, and substitutions will occur to those skilled in the art without departing from the spirit of the invention. Accordingly, the appended claims are intended to include all such variations that fall within the spirit and scope of the invention.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 delete Claim 8 delete Claim 9 delete Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 delete Claim 14 delete Claim 15 delete Claim 16 delete Claim 17 A method of operating a vacuum impregnation system comprising the following steps: (a) placing one or more articles inside a vacuum tank at ambient air pressure; (b) sealing the vacuum tank after step (a); (c) providing a certain amount of impregnation liquid into an inner tank located inside the vacuum tank and also below one or more articles; (d) reducing the internal pressure inside the vacuum tank to less than ambient air pressure after steps (a) and (b); (e) raising the inner tank after steps (c) and (d) so that one or more articles are at least partially immersed in the impregnation liquid; (f) increasing the internal pressure inside the vacuum tank to more than ambient air pressure after step (e); (g) lowering the inner tank to a position where one or more articles are not immersed in the impregnation liquid inside the inner tank after step (f); (h) reducing the internal pressure inside the vacuum tank to ambient air pressure after step (g); and (i) opening the vacuum tank and removing one or more articles from the vacuum tank after step (h). Claim 18 In paragraph 17, a method in which step (c) is performed before and / or simultaneously with step (a) or step (b). Claim 19 In paragraph 17, a method in which step (c) is performed after step (b). Claim 20 A method in which, in paragraph 17, step (d) is performed after step (c) is completed. Claim 21 A method according to claim 17, wherein the vacuum tank comprises a receptacle and a removable lid, and step (a) comprises attaching a rack holding one or more articles to the receptacle. Claim 22 A method according to claim 17, wherein the vacuum tank comprises a receptacle and a removable lid, and step (a) comprises attaching a rack holding one or more articles to the lid. Claim 23 A method according to claim 17, wherein step (c) comprises pumping a certain amount of impregnating liquid from outside the vacuum tank into the inner tank through a flexible passage. Claim 24 A method according to claim 17, wherein an inner tank is attached to a shaft extending through a seal at the bottom of a vacuum tank, step (e) comprises raising the shaft, and step (g) comprises lowering the shaft. Claim 25 A method according to claim 24, wherein step (c) comprises pumping a certain amount of impregnating liquid from outside the vacuum tank into an inner tank through a passage extending through a shaft. Claim 26 A method according to claim 17, further comprising, after step (i), a step of drying one or more articles from a vacuum tank (j) without a crosslinking step. Claim 27 In paragraph 26, the method comprises step (j) air drying or heating to convert the impregnating agent liquid into a solid.

Images