Systems and methods for vacuum impregnation

Abstract

The present invention discloses a vacuum impregnation system and procedure, wherein a part is placed under vacuum, the part is immersed in a polymer impregnation liquid, and positive pressure is applied to the part to introduce the polymer impregnation liquid into the pores of the part, thereby preferably releasing the pressure to atmospheric pressure and curing the polymer impregnation liquid without having an active polymerization step.

Description

Technical Field

[0001] The present invention generally relates to the field of vacuum impregnation systems and procedures, which subject parts to a vacuum, immerse the parts in an impregnation liquid, and apply positive pressure to the parts to introduce the impregnation liquid into the pores of the parts, where the impregnation liquid solidifies. Prior Technology

[0002] Vacuum impregnation systems are used to seal pores and small gaps in objects (such as single parts or assembled parts). This seal helps, for example, reduce or prevent the ingress of water, oil, dirt, and other contaminants into the part or assembly, and helps prevent corrosion of the object. Objects can contain cast metals and other materials, including combinations of metals and plastics. Generally, vacuum impregnation is performed by bringing the object into contact with an impregnating liquid under vacuum, and then, if necessary, applying positive pressure to help move the impregnating liquid into pores and gaps. Vacuum impregnation processes can be classified into two groups: dry vacuum and wet vacuum.

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

[0004] Wet vacuum refers to immersing a part in an impregnation liquid within a vacuum chamber, then applying and maintaining a vacuum until all air is removed from the container and sealant. Wet vacuum presents the challenge of overcoming the hydraulic pressure of the sealant within the vacuum chamber, resulting in less negative pressure in pores and gaps. This has the disadvantage of trapping a limited amount of air in the pores, ultimately leading to poorer 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 pores and gaps within the part.

[0005] Most commonly, the impregnation system uses a low-viscosity monomer solution. After the part is impregnated, the solution is easily removed from the outside of the part by spin or similar mechanical means, leaving liquid in 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, which typically have a viscosity of about 5 mPa·s to about 65 mPa·s (5 centipoise to 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 seal gaps between adjacent metal and plastic parts in certain electronic assemblies (such as cell phone assemblies) during simulated life durability testing.

[0006] To overcome the shortcomings of in-situ polymeric sealing, polymeric impregnation liquids that require no polymerization or crosslinking after impregnation but only drying to form a seal can replace in-situ polymeric monomer solutions. The polymer can be dissolved or dispersed in solvents 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 for drying. Another potential disadvantage is the ineffective sealing of pores and gaps due to shrinkage of the polymer sealant during drying, caused by insufficient polymer solids in the impregnation liquid.

[0007] To address this issue, depending on the non-Newtonian behavior of the polymer (50 centipoise to 3000 centipoise), the applicant selected a viscous (i.e., sticky) polymer material containing higher polymer solids and less solvent, with a viscosity ranging from about 50 Pa·s to up to 3000 mPa·s or more. Viscous polymer solutions or dispersions have been found to provide 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 processes because the head pressure on the liquid solution limits the amount of air that can be removed from pores and gaps, particularly for parts deeper below the liquid surface, where the positive pressure of the liquid and the vapor pressure of any solvent are unfavorable for the vacuum achieved. Combined with the higher viscosity of the polymer impregnating agent, this results in reduced sealing performance. Problems caused by liquid head pressure can be reduced by performing a vacuum impregnation process in a shallow tank, but commercial production of smaller parts will require a large number of relatively large diameter tanks with rated pressure, which will be costly, especially in cases where stainless steel may be required to resist corrosion from certain polymer impregnation liquids.

[0008] The problems associated with wet vacuum processes can be partially solved by using dry vacuum processes. With dry vacuum, container height does not affect seal quality because head pressure does not need to be overcome, and therefore fewer, deeper, smaller diameter tanks can be used for the same production volume. However, dry vacuum processes also have disadvantages. For example, when the viscous impregnating liquid initially enters the vacuum environment of the evacuation tank, it tends to foam violently. This foaming has been observed covering most areas of the vacuum impregnation system, where it dries into a hard coating. Furthermore, unlike thin monomers, the viscous impregnating liquid does not drain well from the sides of the tank at the end of the cycle. Therefore, the foamed impregnating liquid, and any other impregnating liquid that comes into contact with the tank walls during the process, forms a thick, difficult-to-remove deposit on the tank sidewalls after only a few operating cycles. This problem is complicated by the fact that the impregnating liquid is highly viscous and resistant to solvent erosion. Therefore, cleaning the inside of the tank will almost certainly require operator entry into the container, leading to operational complexities such as the need for scheduled downtime and increased demands for operator safety.

[0009] Therefore, the current state-of-the-art technology of vacuum impregnation systems can be further improved. Summary of the Invention

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

[0011] According to one embodiment of the present invention ("Embodiment 1"), a vacuum impregnation system is provided, comprising, substantially consisting of, or consisting of the following: A vacuum chamber, comprising a receiving container and a removable cover, wherein the receiving container and the cover, when the cover is on the receiving container, form a substantially closed vacuum chamber; A rack, which is fixed to or removably supported inside the vacuum chamber and configured to hold one or more objects thereon; An inner tank, movably mounted to the receiving container and configured to hold a certain amount of impregnation liquid therein, the inner tank being movable in a vertical direction between a first position in which one or more objects are not immersed in the impregnation liquid and a second position in which one or more objects are at least partially immersed in the impregnation liquid; and A vacuum and pressure control system, comprising one or more gas control loops, wherein the one or more gas control loops are in fluid communication with the vacuum chamber when the cover is on the receiving container.

[0012] Sample 2. Vacuum impregnation system as in Sample 1, wherein the rack is removably supported inside the vacuum chamber by at least one accessory.

[0013] Sample 3. A vacuum impregnation system as described in any of the preceding samples, wherein the material rack is fixed to the cover or the receiving container.

[0014] Sample 4. A vacuum impregnation system as described in any of the preceding samples, wherein the inner tank is mounted on a shaft extending through the seal at the bottom of the receiving container.

[0015] Sample 5. A vacuum impregnation system as described in any of the preceding samples, wherein the inner groove is removably mounted on the shaft.

[0016] Sample 6. A vacuum impregnation system as described in any of the preceding samples, wherein the shaft includes a linear sliding element.

[0017] Sample 7. A vacuum impregnation system as described in any of the preceding samples, further comprising an actuator attached to the shaft and configured to move the inner groove between the first position and the second position.

[0018] Sample 8. A vacuum impregnation system as described in any of the preceding samples, further comprising a fluid control loop extending from the inner tank to the impregnation liquid source.

[0019] Sample 9. A vacuum impregnation system as described in any of the preceding samples, wherein the fluid control loop includes a flexible passage extending from the inner tank to a fluid port in the receiving container.

[0020] Sample 10. A vacuum impregnation system as described in any of the preceding samples, wherein the fluid control loop includes a passage extending through the shaft.

[0021] 11. A vacuum impregnation system as described in any of the preceding embodiments, 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 a selectively openable vent.

[0022] Sample 12. A vacuum impregnation system as described in any of the preceding samples, wherein the inner tank is coated with a non-stick coating.

[0023] Sample 13. A vacuum impregnation system as described in any of the preceding samples, wherein the inner tank includes a removable inner liner.

[0024] Sample 14. A vacuum impregnation system as described in any of the preceding samples, wherein the inner tube is a reusable or disposable inner tube made of metal or plastic.

[0025] Sample 15. A vacuum impregnation system as described in any of the preceding samples, wherein the inner tank includes a removable inner circumferential belt positioned inside the inner tank.

[0026] Sample 16. A vacuum impregnation system as described in any of the preceding samples, 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.

[0027] According to another embodiment of the present invention ("Embodiment 17"), a method for operating a vacuum impregnation system is provided, the method comprising the following steps, substantially consisting of the following steps or consisting of the following steps: (a) Positioning one or more objects in a vacuum chamber under ambient pressure; (b) After step (a), seal the vacuum chamber; (c) A certain amount of impregnation liquid is provided in an inner tank located inside the vacuum tank and below the one or more objects; (d) After steps (a) and (b), the internal pressure inside the vacuum chamber is reduced to below the ambient pressure; (e) After steps (c) and (d), the inner tank is raised to immerse at least partially the one or more objects in the impregnation liquid; (f) After step (e), the internal pressure inside the vacuum chamber 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 objects are not immersed in the immersion liquid within the inner tank; (h) After step (g), the internal pressure inside the vacuum chamber is reduced to ambient pressure; and (i) After step (h), the vacuum chamber is opened and the one or more objects are removed from the vacuum chamber.

[0028] 18. The method of any of the preceding states, wherein step (c) is performed before and / or simultaneously with step (a) or step (b).

[0029] State 19. The method of any of the aforementioned states, wherein step (c) is performed after step (b).

[0030] State 20. The method of any of the aforementioned states, wherein step (d) is performed after step (c) is completed.

[0031] Sample 21. The method of any of the preceding samples, wherein the vacuum tank includes a receiving container and a removable cover, and step (a) includes attaching a rack holding the one or more objects to the receiving container.

[0032] Sample 22. The method of any of the preceding samples, wherein the vacuum tank includes a receiving container and a removable cover, and step (a) includes attaching a rack holding the one or more objects to the cover.

[0033] 23. The method of any of the preceding embodiments, wherein step (c) includes pumping the amount of impregnating liquid from outside the vacuum tank through a flexible passage and pumping it into the inner tank.

[0034] Version 24. The method of any of the preceding versions, wherein the inner groove is attached to a shaft extending through the seal at the bottom of the vacuum groove, and step (e) includes raising the shaft, and step (g) includes lowering the shaft.

[0035] Sample 25. The method of any of the preceding samples, wherein step (c) includes pumping the amount of impregnating liquid from outside the vacuum tank through a passage extending through the shaft and pumping it into the inner tank.

[0036] 26. The method of any of the aforementioned states further includes (j) drying the one or more objects from the vacuum chamber without crosslinking after step (i).

[0037] Sample 27. The method of any of the preceding samples, wherein step (j) includes air drying or heating to convert the impregnating agent liquid into a solid.

[0038] In one embodiment, the dry vacuum impregnation system includes a tank-within-a-tank structure, wherein the impregnating polymer is contained in a top-open inner tank disposed within a pressure-resistant outer tank, the outer tank having a closed lower portion and an upper portion terminating with a sealable opening. The inner tank is positioned below the upper portion of the outer tank, and the parts to be impregnated are introduced into the upper portion through the sealable opening. Instead of moving the impregnating polymer between containers, the inner tank containing the polymer is movably positioned within the outer tank, and in use, the inner tank is moved upward to surround the parts to be coated until the parts are immersed in the impregnating polymer. In this way, foaming of the impregnating polymer due to turbulence between the reservoir and the vacuum impregnation tank, and over-foaming caused by introducing the polymer into a vacuum tank, are significantly reduced.

[0039] With the polymer solution contained at the bottom of its traverse in the inner tank, the parts to be sealed are preferably lowered into the outer tank by a lift or similar means, suspending the parts above the polymer liquid, typically on a rack or other support. Next, the top of the outer tank is closed, sealing the pressure-resistant outer tank, and air is evacuated from the pressure-resistant outer tank (containing the orifices / gap of the parts) of the vacuum impregnation system. The inner tank then moves upward to immerse the parts in the polymer solution and release the vacuum, which helps move the polymer liquid into the gaps and orifices. The outer tank is then pressurized to above atmospheric pressure, forcing additional viscous polymer into the orifices / gap of the parts. After a selected time (approximately 30 to 300 seconds), the pressure is released and returned to atmospheric pressure, the inner tank is lowered, and excess polymer drips from the outer surface of the parts and the rack back into the inner tank. Raise the rack, place a collection tray for excess polymer below the rack if necessary, then remove the rack and transport it to the cleaning station (where excess polymer is removed from the surface of the part) and then to the drying station (where the polymer is allowed to dry), which converts the viscous polymer liquid into a solid form (whereby it has elastomeric properties) to seal the pores and gaps of the object.

[0040] It is worth noting that when using dry vacuum, the vacuum impregnation vessel does not need to have a large area occupied by multiple shallow grooves to accommodate the head pressure issues of the wet vacuum process. Therefore, deeper grooves with smaller diameters can be used without adversely affecting the sealing quality. Simple Explanation of the Diagram

[0041] Figure 1 is a schematic diagram of an exemplary vacuum impregnation system. Figure 2 illustrates the embodiment of Figure 1 in the first operating state. Figure 3 illustrates an alternative embodiment of the exemplary impregnation system in the first operating state. Figure 4 illustrates the embodiment of Figure 1 in the second operating state. Figure 5 illustrates the embodiment of Figure 1 in the third operating state. Figure 6 illustrates an exemplary method for operating a vacuum impregnation system. In the diagram, the same element symbols indicate the same feature. Implementation

[0042] The embodiments described herein relate to a vacuum impregnation system and a method for operating the vacuum impregnation system. It will be understood that the embodiments discussed herein are illustrative, and other embodiments may cover various different forms or combinations of features described herein.

[0043] Figure 1 illustrates a first exemplary embodiment of a vacuum impregnation system 100. The system 100 includes a vacuum chamber formed by a receiving container 102 and a cover 104. The receiving container 102 is configured as the lower portion of the vacuum chamber and is generally fluid-tight. The cover 104 is configured as the upper portion of the vacuum chamber and is also generally fluid-tight. The receiving container 102 terminates at its upper end with an upward opening 106, and the cover 104 has a similarly shaped downward opening 108. The cover 104 is securely attached to the receiving container 102 to form a generally fluid-tight and pressure-tight vacuum chamber 112. One or both of the openings 106 and 108 are surrounded or contained by an O-ring 110 or other(s) seals, which may be provided on a radially extending flange to assist in forming a generally fluid-tight enclosure. As used in this article, "bulk fluid seal" means that when all operating passages and openings are closed, no gas or liquid, or only a nominal amount of gas or liquid that does not affect the operation of the system, can pass through the structure.

[0044] The receiving container 102 and the cover 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, the receiving container 102 and the cover 104 may together be formed in a spherical or other shape. The vacuum chamber can be configured to accommodate the desired operating pressure and vacuum, and to withstand the expected operating temperature. For example, the vacuum chamber can be rated for operation within a range from 10 mm Hg vacuum to 20 atmospheres, or more preferably from 20 mm Hg vacuum to 10 atmospheres. The vacuum chamber can also be rated for operation at 5°C to 200°C, and more preferably from 5°C to 100°C.

[0045] System 100 also includes a rack 114 (or multiple racks), configured to be positioned within a vacuum chamber 112, fixed to or removably supported within the vacuum chamber. The rack 114 or multiple racks may be fixed to one or both of a receiving container 102 and a cover 104. The rack 114 is preferably removably supported and / or secured within the vacuum chamber. For example, the receiving container 102 may include an inner lip 116 extending radially inward from its inner wall surface 118, and the rack 114 may include an outer lip 120 extending radially outward from the rack 114 to engage the inner lip 116 and hold the rack 114 at a predetermined vertical position within the vacuum chamber 112. Other embodiments may use other mechanisms, such as hooks or the like, to secure the rack 114 to the receiving container 102 or the cover 104.

[0046] The connecting mechanism can be configured for automatically mounting the rack 114 and removing it from the vacuum chamber 112. For example, the inner lip 116 and outer lip 120 can be configured to support the rack 114 in the vertical direction, but allow some radial and rotational movement to compensate for inaccuracies in the operation of the loading equipment (e.g., a crane or ceiling lift). If needed, mechanisms such as bolts or clamps can be provided for securing the rack in position in all directions to prevent any movement of the rack 114 once it is in place. Other alternatives and variations will be appreciated by those skilled in the art in light of the invention.

[0047] In other embodiments, the rack 114 may be permanently attached to the receiving container 102 or the cover 104. For example, the rack 114 may be welded into place or secured by fasteners that do not allow removal of the rack during normal operation and cleaning procedures. In this case, removable retainers, supports, baskets, and the like (described further below) may be used to position the parts in the rack for immersion and, where appropriate, transportation.

[0048] The rack 114 is also configured to hold one or more objects to be vacuum impregnated and to allow the impregnation liquid to contact the objects. For example, the rack 114 may include a wire basket or a series of nested wire baskets supporting the objects from the bottom, or hooks capable of holding one or more corresponding openings in the objects. The rack 114 may also be configured to suspend objects or objects without immersing the rack 114 in the impregnation liquid. For example, each object may be suspended from the rack 114 by means of an intermediate disposable connector (such as a strand or a ring of plastic material). In view of the invention, other alternatives and variations will be appreciated by those skilled in the art.

[0049] System 100 further includes an inner tank 122, which is generally closed at its lower end to retain a certain amount of impregnation liquid, but has an open top 124 that is sized and shaped to receive the rack 114 and / or objects held or suspended from the rack. For example, the inner tank 122 may include a cylindrical chamber with a diameter slightly smaller than the diameter of an adjacent portion of the inner wall surface 118 of the receiving 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 tube 122' (such as a reusable or disposable inner tube of metal or plastic material), which is intended to facilitate periodic cleaning of the inner tank 122 and allow for the selection of cheaper materials for manufacturing the inner tank 122 and the receiving container 102. For example, for surfaces not in direct contact with the polymer-impregnated liquid (which may be corrosive), a lower grade of steel (such as carbon steel, aluminum, or other suitable metals that do not interfere with the purpose of this invention) can be used instead of stainless steel.

[0050] The inner tank 122 is movably mounted to the receiving container 102 such that it can move vertically between a first position in which the object held by the rack is not immersed in the immersion liquid in the tank and a second position in which the object is at least partially (and preferably fully) immersed in the immersion liquid. The operation of the inner tank 122 is described in more detail below.

[0051] The inner groove 122 can be movably mounted to the receiving container 102 using any suitable mechanism. In the illustrated example, the inner groove 122 is mounted on a shaft 126 extending through a seal 128 at the bottom of the receiving 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 may comprise a polished stainless steel cylinder extending through an opening penetrating the bottom of the receiving container 102 to mount one or more mechanical or gland seals in the opening, and extending radially to contact the shaft 126 to form a sliding seal 128. The seal 128 may comprise any suitable configuration of a scraper, sealing lip, compression ring, O-ring, V-ring, wedge, packing, or the like, as known in the field of hydraulic seals. In this case, the shaft 126 is a linear sliding member that moves axially along its length without needing to rotate about its axis. In other cases, shaft 126 may include a lead screw with an internal thread that engages the bottom of receiving container 102, or have other configurations.

[0052] Actuator 130 is attached to shaft 126 and configured to move inner groove 122 between a first (lowered) position and a second (raised) position. In the illustrated example, actuator 130 includes a hydraulic or pneumatic piston 132 and cylinder 134 assembly, which is powered by pressurizing the cylinder chamber, as is known in the art. In this case, piston 132 is attached to shaft 126 by rigid connection 136. Therefore, operating actuator 130 moves piston 132 upward, thereby moving inner groove 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 may be fixed in place, and cylinder 134 may be connected to shaft 126. As another example, shaft 126 may be shaped to be directly fitted into a corresponding hydraulic or pneumatic cylinder. As another example, the connector 136 may include one or more mechanisms, such as chains and sprockets, belts and pulleys, gears, transmissions, levers, linkages, or the like, 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 power source. The specific characteristics of the actuator 130 and its connection to the shaft 126 are not critical to the invention, and many variations will be understood in light of the invention.

[0053] The vacuum impregnation system 100 also includes a fluid control circuit 138 configured to supply impregnation liquid to the inner tank 122. The fluid control circuit 138 includes any suitable configuration of valves, passages, and / or pumps for supplying impregnation liquid to (and, where appropriate, from) the inner tank 122. For example, the fluid control circuit 138 may include a pump 140 and an impregnation liquid valve 142 connected in series fluidly to an impregnation liquid source 144 (e.g., a tank or supply passage).

[0054] The fluid control loop 138 can be connected to the inner tank 122 via various configurations of the fluid passage. In the example of FIG1, a flexible passage 146 extends from the inner tank 122 to a fluid port 148 that travels through the receiving container 102. The fluid port 148 can be configured with any suitable fitting (e.g., a pipe or the like with or without threaded connections), as is well known in the field of pressure vessel design. The flexible passage 146 may include a flexible hose or the like and is sized to allow the inner tank 122 to move between a first position and a second position without impeding the movement of the inner tank 122 or obstructing the hose, and preferably has abrasion resistance 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 appreciated by those skilled in the art in light of the invention.

[0055] As also shown in Figure 1, the fluid control circuit 138 can alternatively be connected to the inner tank 122 via a passage 150 extending through the shaft 126. This eliminates the need to provide a flexible passage 146 within the tank environment, but a flexible passage 152 may be required to connect the shaft passage 150 to other parts of the fluid control circuit 138.

[0056] Embodiments using flexible passage 146 or shaft 150 to deliver impregnation liquid to inner tank 122 both provide the option of selectively removing impregnation liquid from inner tank 122 by flushing in the countercurrent direction or pumping. This can facilitate returning impregnation liquid to a storage tank for later use, preparing inner tank 122 for cleaning, or provide other advantages.

[0057] However, in other embodiments, the fluid control circuit 138 may be configured to deliver the impregnating liquid only to the inner tank 122. For example, the fluid control circuit 138 may deliver the impregnating 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 receiving container 102 at a position above the open top 124 when the inner tank 122 is in a first position. 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 circuit 138 may also be configured to pour the impregnating liquid into the inner tank 122 through the upper end 106 of the receiving container 102 before attaching the cap 104. Other alternatives and variations will be apparent to those skilled in the art in light of the invention.

[0058] It is also envisioned that multiple inner grooves 122 may be used in some embodiments. These multiple grooves 122 may facilitate the vacuum impregnation of a number of objects or the vacuum impregnation of a small batch of objects using different impregnation liquids without filling the entire volume of a single inner groove 122. The multiple inner grooves 122 may move together (e.g., attached to the same shaft 126 or provided as a discrete subdivision of a single uniform structure), or may move individually (e.g., mounted on separate shafts and having separate operating systems).

[0059] The inner tank 122 can also be removable, allowing for cleaning without personnel entering the receiving container and facilitating continued processing of parts using a replacement tank. The inner tank 122 can also be replaced with tanks of different sizes or filled to different liquid levels for vacuum immersion of different objects or combinations of objects.

[0060] The inner tank 122 may be fitted with a removable inner circumferential belt positioned approximately inside the inner tank at the surface of the impregnating liquid (e.g., the air / impregnating agent interface). The belt forms a flat ring that presses against the inner surface of the inner tank 122 and may be, for example, a spring-loaded metal ring. The belt isolates the inner tank from the impregnating liquid at the air / impregnating agent interface and can collect polymer deposits generated on the belt surface during treatment, thereby facilitating easy removal of the deposits. This feature may be used in place of or in combination with the inner cylinder 122'.

[0061] The vacuum impregnation system 100 also includes a vacuum control system that is 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 ​​for reducing the gas pressure inside the vacuum chamber 112 to be lower than the ambient pressure outside the vacuum chamber; a second gas control loop 156 for increasing the gas pressure in the vacuum chamber 112 to be higher than the ambient pressure outside the vacuum chamber; and a third gas control loop 158 for equalizing the pressure inside the vacuum chamber 112 with the ambient pressure outside the vacuum chamber.

[0062] Gas control loops 154, 156, and 158 may be configured with any suitable device to provide the desired functionality. For example, in the illustrated embodiment, the first gas control loop 154 ​​may include a first valve 160 connecting a vacuum tank to a vacuum pump 162, the second gas control loop 156 may include a second valve 164 connecting a vacuum tank to a compressor 166, and the third gas control loop may include a third valve 168 connecting a vacuum tank to ambient air. Components of the vacuum control system may also include other devices such as filters, liquid traps, gauges, and the like. Any automatic or manual operating control system may 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 invention.

[0063] The vacuum impregnation system 100 also preferably includes a liquid drain circuit 170 (such as a liquid drain valve 172), which is configured to drain impregnation liquid, condensate and any other liquid from the bottom of the vacuum tank.

[0064] The selection and use of valves, vacuum pumps, compressors and the like are well known in the field of vacuum impregnation systems and do not require further discussion in this document.

[0065] Figures 2 through 6 illustrate exemplary methods for operating the vacuum impregnation system 100 and other embodiments. The exemplary procedure begins with loading the object 200 to be sealed onto the rack 114 (step 600), loading the rack 114 onto the receiving container 102 or the cover 104 (step 602), and sealing the vacuum chamber by securing the cover 104 to the receiving container 102 (step 604). Steps 600 and 602 can be performed in any order (i.e., the object 200 can be loaded onto the rack 114 before or after securing the rack 114 to the receiving container 102 or the cover 104). Figure 2 shows the object secured to the rack 114 before it is secured to the receiving container 102. Figure 3 shows the rack 114 secured to the cover 104 as an alternative embodiment. If the rack 114 is permanently attached to the vacuum chamber, step 602 is satisfied by default. Figure 4 shows the rack 114 securely attached to the vacuum tank and the cover 104 securely attached to the receiving container 102 for forming a sealed vacuum chamber 112.

[0066] In step 606, the inner tank 122 is filled to the desired level with impregnation liquid 202. Step 606 can be performed before or after sealing the cap 104 to the receiving container 102. For example, Figure 2 shows impregnation liquid 202 at a low level (or not at all) during loading of the rack 114, and the impregnation liquid 202 can be maintained at this level until the cap 104 is sealed to the receiving container 102. In contrast, Figure 3 shows impregnation liquid 202 filled to the working level before sealing the cap 104 to the receiving container 102.

[0067] Step 608 is performed after the cap 104 is sealed to the receiving container 102. In step 608, a vacuum is created in the vacuum chamber 112, such as by operating the first gas control circuit 154 to pump ambient air out of the vacuum chamber 112. If necessary, one or more flushing steps may be performed before step 608 to help remove gases from the ambient air that may interfere with the procedure. For example, nitrogen may be pumped into the vacuum chamber 112 to replace the ambient air before performing step 608.

[0068] Step 608 is preferably performed after filling the inner tank 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 a significant improvement by facilitating easier, safer, and / or less frequent cleaning of the vacuum tank. However, by introducing the impregnation liquid 202 into the area of ​​the inner tank 122, the problem associated with foaming can be isolated, at least to some extent, from the inner tank 122. In this case, most of the cleaning procedure will concern cleaning the inner tank 122, and this procedure can be facilitated by making the inner tank 122 removable (e.g., by attaching it to the shaft 126 with nut 174 or (some) other fasteners) or by providing a removable inner cylinder 122' in the inner tank 122. Therefore, embodiments may perform the vacuum generation step 608, either before or simultaneously with the introduction of the impregnation liquid in step 606.

[0069] Next, in step 610, the inner tank 122 is raised by operating the actuator 130 until the object 200 to be vacuum-impregnated is immersed in the impregnation liquid 202. The object 200 may be fully immersed or, if not required to be impregnated entirely, only to the desired extent. During immersion, the impregnation liquid surrounds the object and the spaces and gaps to be filled, and can penetrate these pores and gaps to a certain extent.

[0070] Step 610 is performed after step 608 to make this a dry vacuum impregnation process (i.e., a vacuum is created before immersion of the object 200). This is intended to reduce or eliminate inconsistent impregnation of the object at different locations within the vacuum chamber 112, as the vacuum created in the pores does not counteract the pressure of the hydraulic head generated by the impregnation liquid. This allows the vacuum tank to be relatively large in the vertical direction, resulting in a greater throughput for a given capital investment in the processing equipment.

[0071] When the object 200 is immersed, the program moves to step 612, in which the second gas control circuit 156 is operated to raise the pressure inside the vacuum chamber 112 to above atmospheric pressure. Raising the pressure in the sealed receiving container causes the impregnating liquid to enter through evacuated orifices and gaps to provide a modified seal.

[0072] Next, in step 614, the inner tank 122 is lowered by operating the actuator 130 until the immersion liquid is below the lowest item 200 on the rack 114, and the item 200 is removed from the immersion liquid. During and after this step, any residual immersion liquid 202 on the item 200 can be drained from the item 200 into the inner tank 122 for reuse or recycling.

[0073] Finally, in steps 616 and 618, the vacuum chamber 112 is emptied by operating the third gas control circuit 158, and the object 200 is removed.

[0074] It will be understood that some or all of the aforementioned procedural 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 612, the duration of immersion in step 610, the waiting time before emptying the tank in step 616, and so on. Additionally, the temperature of the object 200, the atmosphere in the vacuum chamber 112, and all of the immersion liquid 202 can be adjusted. The precise expected values ​​or ranges of these variables can be determined through experimental trials.

[0075] The intended embodiments are particularly useful when used with relatively viscous impregnating liquids, which may be selected to have more or less adhesive properties depending on whether the object is an assembly that requires disassembly for maintenance. Preferably, the impregnating liquid is chosen to provide a uniform and consistent seal formation, wherein a durable seal is formed between the sealing material and a wide variety of materials constituting the assembly, 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 (preferably water) to complete the seal. An inert polymer will be understood by those skilled in polymer technology to mean a polymer that lacks sufficient groups to impart a particular chemical reactivity to the polymer. Suitable inert polymers may include (by non-limiting examples) polyacrylates, polyvinyl alcohol, polyurethanes, polyvinyl acetate, and the like. The impregnation liquid may contain additives known for formulating adhesives and sealants, such as rheology modifiers, wetting agents, anti-aging agents, stabilizers, bio-stabilizers, and / or color pigments. Generally, depending on the non-Newtonian behavior of the polymer (50 centipoise to 5000 centipoise) solution, viscous impregnation polymer materials have a viscosity ranging from about 50 Pa·s to up to 5000 mPa·s or higher.

[0076] The embodiments can be configured to seal pores and gaps in a variety of objects, including objects having both metal and plastic parts. Exemplary objects include, but are not limited to: telecommunications equipment (e.g., radios, cellular telephones, etc.); audio equipment (e.g., headphones, speakers, microphones); and other electronic equipment, such as computers, processing units, electronic controllers, wire harnesses, electrical connectors, and the like.

[0077] As previously mentioned, although the invention has been illustrated and described herein with reference to specific embodiments, the invention is not intended to be limited to the details shown. In fact, various modifications to the details may be made within the scope and within the equivalents of the claims and without departing from the invention.

[0078] In this specification, embodiments have been described in a manner that allows for a clear and concise description; however, it is anticipated and will be 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 forms of the invention described herein.

[0079] While preferred embodiments of the invention have been shown and described herein, it will be understood that these 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 that fall within the spirit and scope of the invention.

[0080] 100: Vacuum Impregnation System 102: Collect the container 104: Cover 106: Opening / Top 108: Opening 110: O-ring 112: Vacuum Chamber 114: Material rack 116: Inner lip margin 118:Inner wall surface 120: Outer lip margin 122: Inner groove 122': Inner tube 124: Open Top 126: Shaft 128: Seals 130: Actuator 132: Piston 134: Cylinder 136: Connector 138: Fluid control loop 140: Pump 142: Impregnated liquid valve 144: Source of impregnation liquid 146: Flexible pathway 148: Fluid Port 150:passage 152: Flexible pathway 154: First gas control loop 156: Second gas control loop 158: Third Gas Control Loop 160: First valve 162: Vacuum pump 164: Second valve 166: Compressor 168: Third Valve 170: Liquid drain circuit 172: Liquid drain valve 174: Nut 200:Object 202: Impregnation liquid / Impregnation solution 600: Steps 602: Steps 604: Steps 606: Steps 608: Steps 610: Steps 612: Steps 614: Steps 616: Steps 618: Steps

Claims

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

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

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

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

5. The method of claim 1, wherein the vacuum tank includes a receiving container and a removable cover, and step (a) includes attaching a rack holding the one or more objects to the receiving container.

6. The method of claim 1, wherein the vacuum tank includes a receiving container and a removable cover, and step (a) includes attaching a rack holding the one or more objects to the cover.

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

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

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

10. The method of claim 1, further comprising (j) drying the one or more objects from the vacuum chamber without crosslinking after step (i).

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

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