Methods and equipment for controlling the temperature of solid particles and an interstitial medium

Abstract

Methods and equipment for controlling the temperature of particles in polishing processes using solid particles and / or solid particles with an electrolyte inside a container. The method includes a step in which a gas is circulated through the environment between the particles located inside the container. The method may also include a simultaneous or prior step of adjusting the chemical composition of the particles or of the environment. The equipment includes means for injecting a gas, which in some cases is injected from the bottom of the container, the means fro injecting a gas including an aero-flotation device and, optionally, also a moisturizing device for suspending droplets of a liquid in the gas.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application relates to and claims the benefit and priority to International Application No. PCT / ES2024 / 070343, filed Jun. 3, 2024, which claims the benefit and priority to Spanish Patent Application No. P202330447, filed Jun. 2, 2023, each of which is each incorporated herein by reference in its entirety.OBJECT OF THE INVENTION

[0002] The invention relates to methods and equipment for controlling the temperature of particles in polishing processes by means of solid particles, which provide advantages and features to the function for which it is intended and which are described later on in detail. The object of the present invention relates to a method applicable to polishing processes or surface treatment of materials by means of solid particles, particularly relevant in electropolishing systems by means of solid particles loaded with an electrolyte and located inside a container, with the aim of controlling the temperature of the particles. During the polishing or electropolishing process by means of solid particles, a lack of temperature control may occur either due to the Joule effect generated during conduction of electrical current through the particles or the part to be polished, or due to friction or a combination of both effects. These temperature fluctuations can affect both the results of the surface treatment and the degradation of the solid particles, thereby reducing their useful life, affecting the conductivity and therefore the effectiveness of the treatment, which may no longer be homogeneous and / or repetitive.FIELD

[0003] The field of application of the present invention falls within the industry sector dedicated to surface treatment, encompassing the industrial sector dedicated to the treatment of metal surfaces, with applications in any field, and particularly covering electropolishing processes by means of solid particles.BACKGROUND

[0004] Methods for polishing surfaces in which the parts to be treated are polished by friction and / or through conductive particles incorporated into a container are known in the state of the art.

[0005] For example, document PCT / ES2017 / 070247 discloses a “Method for smoothing and polishing metals via ion transport by means of free solid bodies, and solid bodies for carrying out said method”, which, after the connection of the parts to be treated to the positive pole (anode) of a current generator, includes the friction of the part with a set of particles made up of free electrically conductive solid bodies charged with a negative electrical charge and the introduction of said parts into a container or tank, in friction with a set of particles that are incorporated into said container and that contact electrically with the negative pole (cathode) of the current generator.

[0006] One problem associated with said method is that during the polishing process by means of solid particles containing an electrolyte inside a container or tank, the particles vary their temperature due to physical phenomena that occur during the surface treatment process, such as conduction of current or friction forces.

[0007] This variation in temperature may alter the result of the treatment and degrade the solid particles, causing a decrease in their useful life. Furthermore, a change in temperature also affects qualities such as conductivity, and therefore the polishing process, which depends on the conductivity of the process, is not homogeneous and / or repetitive. This means that, depending on the temperature of the particles, the polishing process is one or another, which may not be acceptable for the desired result in certain products.

[0008] Therefore, an objective of the present invention is the development of a method and equipment for controlling the temperature of particles.

[0009] The existence of temperature control systems in polishing systems, either by liquid recirculation or by direct contact by means of heat exchangers, is known. By applying these methods in a polishing system by means of solid particle friction and / or conductive solid particles, it is not possible to achieve sufficient thermal control to ensure optimal, homogeneous, constant and repetitive results. By applying thermal regulation by recirculating the product through a circuit through which heat is exchanged, as can be found in conventional electropolishing systems. In this case, there is a problem associated with the inability to pump the particles, since they are not inside a fluid that does not meet the features for the assembly to be pumpable. Given the difficulty in recirculation and the high probability of clogging the recirculation system, thermal control using this method is not possible.

[0010] The systems that the following invention applies to are defined by discrete media in the form of particles and do not exhibit physical continuity between the elements. When attempting to carry out thermal control, introducing a resistive or conductive element that acts as a heat exchanger, either as a heat pump or refrigeration machine, by immersion into the system, the greatest difficulty encountered by the particles to transfer heat when compared to other liquid systems involves an ineffective and highly heterogeneous system. In the event that the solid particles are some types of ceramic or polymer materials, the efficiency of the thermal control process is reduced since they have a low thermal conductivity.

[0011] In the same way as previously described, thermal control by means of a heat exchanger system located at the periphery of the container is inefficient, since an excessive thermal gradient would be obtained from the center to the periphery thereof.

[0012] The present invention aims to provide a method and mechanism with efficient temperature control that can be carried out prior to, during or after the surface treatment, and which overcomes the difficulties set out above.DESCRIPTION OF THE INVENTION

[0013] The present invention proposes a method applicable to polishing processes by means of solid particles and / or solid particles with an electrolyte, which purpose is to control the temperature of the polishing means. The present invention aims to generate the circulation of a gas through the interstitial environment between particles with the ability to adjust the temperature of both the interstitial medium and the particles. Furthermore, by circulating a gas through the interstitial environment between particles, it offers the possibility of adjusting the chemical composition of the particles and / or their environment by including micro-droplets of some liquid suspended in said gas.

[0014] An uncontrolled increase in the temperature produced in the process due to the Joule effect during conduction of current, which may degrade the particles, thereby reducing their useful life, and / or affecting the conductivity and therefore the effectiveness of the treatment, which may no longer be homogeneous and / or constant, for example, may be avoided by means of temperature control. In other situations, the temperature of the particles and / or their environment may be raised above the environmental conditions by means of temperature control, in order to find a more thermodynamically efficient condition that promotes greater particle kinetics or better polishing results.

[0015] The method and the aero-flotation equipment that are used for controlling the temperature of particles and their environment in polishing processes by means of solid particles proposed by the invention are configured to address the issues discussed above.

[0016] The aero-flotation equipment may be defined as a mechanism by means of which the gas, with which the solid particles will be thermally controlled, is injected from the bottom of the container and with a homogeneous distribution in the injection pressure throughout the injection base.

[0017] As noted above, an embodiment of the invention proposes a method applicable to polishing processes by means of solid particles with an electrolyte therein and housed in a container, which purpose is to control the temperature of the polishing means, in some cases, preventing an uncontrolled increase in the temperature produced in the process due to, for example, the Joule effect that occurs during conduction of current, which may degrade the particles, thereby reducing their useful life, or affecting their conductivity and therefore the effectiveness of the treatment, which may no longer be homogeneous and / or constant.

[0018] In other embodiments of the invention, the objective of the method for controlling temperature is to increase the temperature of the particles and / or their environment above the environmental conditions in order to increase the thermodynamic efficiency of the process and promote greater kinetics, accelerating the surface treatment and / or obtaining better finishes.

[0019] Furthermore, in dry electropolishing systems by means of conductive solid particles, moisture, pH or the amount of acid or the presence of moderating liquids are also an important factor to ensure the conductivity of the dry electropolishing particles. Especially dry particles or particles with a low acid concentration do not offer as much conductivity as wet particles or particles with a higher acid concentration. It has been observed how temperature can disturb the initial chemical conditions mentioned above, which means that temperature control has a direct impact on the results of the surface treatment.

[0020] An embodiment method according to the present invention includes the circulation of a gas, in some cases preferably air, from the bottom of the container, such that it controls the temperature of the particles, further contemplating the possible application of hydration or impregnation of said particles in contact with the gaseous environment to avoid the reduction in moisture caused by said aero-flotation, either by spraying a liquid, such as water, onto the particles or injecting the gas with a high moisture or moistening content.

[0021] Furthermore, in a particular embodiment of the invention, aero-flotation equipment applicable to, for example, the bottom of a container of a polishing system by means of solid particles is used to carry out said temperature control method by means of, for example, injection of gas and hydration or impregnation of some liquid.

[0022] One method comprises a step in which circulation of a gas is forced through the container, such that the gas circulates through the medium located between the particles, causing heat exchange through convection or other mechanisms between the gas and the particles and their environment, resulting in an adjustment of the working temperature. Based on the temperature difference between the gas and the interstitial medium containing the particles, it is possible to regulate the resulting temperature of the particles and the interstitial medium. It is possible to dynamically regulate the temperature of the circulation gas based on the reading of a sensor or thermocouple in contact with the particles, and thus dynamically adjust the working temperature.

[0023] The forced circulation of the gas in the interstitial medium is obtained in some cases by means of an injection process, in other cases by means of aspiration, and in others, a combination of both effects.

[0024] As mentioned previously, the inlet of gas into the container with the particles is preferably carried out from the bottom. In other configurations, circulation of the gas is forced by means of perimeter injection along different heights in a container with any type of polygonal section. In another configuration, the gas is expelled through an element integral with the fastening system of the part, and which serves to move it within the polishing means, either focused on it or focused in other directions. In another configuration, recirculation is forced on the surface of the container containing the particles.

[0025] In one embodiment using aero-flotation equipment, circulation of the gas through the particles is carried out from the lower part or bottom of the container, so that the gas rises and acts on the particles, cooling them. In addition to the thermal adjustment of the medium between the particles by means of convection, the gas injection process from the bottom of the container results in an increase in the partial pressure of said gas that is interposed in the medium between particles, which modifies the rheology of the particles and the pressure they exert when coming in contact with the part. All of this results in an additional reduction in the heat generated during polishing, modifying the aerodynamics of the polishing process and thus preventing the occurrence of defects on the part to be treated and improving the final polishing result. Greater fluidity of the assembly, thanks to this embodiment, promotes greater ease for the particles to adapt to the entire geometry of the part to be polished that moves inside the container, which prevents the occurrence of areas with a lesser surface finish due to downwind or turbulence. In turn, having a higher partial pressure of the gas injected into the interstitial space decreases the pressure exerted by the particles on the surface of the part, which results in a lower level of final attainable roughness.

[0026] In one embodiment the gas is injected into a lower chamber through channels, preferably micro-perforated, and from this lower chamber it enters into the container with the particles through a membrane that closes the top of the chamber. Thus, entry into the entire lower surface of the container is ensured and, therefore, temperature is controlled throughout the container.

[0027] Preferably, the gas injected into the system is generated by a compressed gas compressor. The method described in the invention is not limited to the fact that in another embodiment it is possible to recirculate the gas by suction carried out, for example, by a vacuum pump. Thus, in a preferred embodiment of the invention, the equipment for controlling the temperature of particles in polishing processes by means of solid particles comprises means for injecting gas from the bottom of the container.

[0028] In one embodiment, preferably intended for polishing processes in a gaseous environment, the gas injection means comprises an aero-flotation device which, in turn, comprises a chamber made of PVC, or another material, in the form of a frame, suitable to fit in the bottom of the container, inside of which it has a blowing manifold with channels, preferably micro-perforated, that connect to an inlet duct for the gas driven under pressure from a compressor, and a very fine mesh membrane that closes the chamber at the top, which acts as a means for homogenizing the gas that passes therethrough towards the container. With this, when the chamber is filled, the membrane receives pressure and generates a cushion of gas throughout the base of the container that, when passing through, rises homogenized in the form of microspheres of gas that cool the particle content in the container.

[0029] Since it is a polishing process in which a gas is forced to circulate between the interstitial environment of the particles, this process can be carried out by injecting the gas with the help of a device that causes an aero-flotation effect, thanks to which a flow of cold gas is generated to displace the hot gas that, at the same time, produces heat exchange with the particles.

[0030] It is important to note that, since it is a polishing process in a gaseous environment, the gas, which can be any other gas, dries the particles and causes an endothermic reaction that captures the heat of the particles, thus lowering the temperature but also removing moisture from them. To counteract this reduction in moisture caused by the injection of gas, since, as mentioned in previous sections, moisture is also an important factor to ensure the conductivity of the particles and if they are especially dry, they do not offer as much conductivity as the wet particles, the method object of the invention preferably contemplates a simultaneous or prior step of hydrating the particles. In one embodiment the step of hydrating the particles is carried out simultaneously with the injection of gas by spraying a liquid, such as water, onto the particles in the container or tank, by means of injectors oriented towards the inside of the container, preferably located on the container.

[0031] In another embodiment hydration is carried out by injecting the gas, such as air, with a high moisture content. Therefore, a secondary objective of the invention is to provide methods and equipment for controlling the temperature of particles by injecting gas that, at the same time, ensures correct control of electrochemical conditions, such as moisture, pH, additives thereof to avoid an excess or deficit of conductivity and / or galvanic capacity when the process is carried out in a gaseous environment. For this, preferably, prior to injecting gas into the container, the gas is injected into a vessel with a liquid, preferably water, the gas passes through the vessel with the liquid, gaining moisture, and then it is injected into the container containing the particles.

[0032] In another embodiment, said hydration process can be complemented with an acid dissolved in a polar liquid, such as water, in such a way that it also allows its pH to be controlled, the acid being, for example, sulfuric acid, sulphonic acid, hydrochloric acid, hydrofluoric acid, phosphoric acid, nitric acid.

[0033] In another embodiment, the liquid suspended in the gas is a non-conductive additive or element, such as some type of oil, which acts as a moderator of the conductivity or the electrochemical interaction between the particles and the part, preventing, for example, the occurrence of uncontrolled chemical attacks on the part. Said additives can be non-polar liquids such as short aliphatic chains. The moderating liquids can incorporate surfactants in their presence that modify the interactive capacity between particles and between the particles and the surface to be treated.

[0034] Furthermore, in one embodiment, the equipment for controlling the temperature of particles in polishing processes by means of solid particles in a gaseous environment further comprises a device for hydrating the compressed gas that is injected into the aforementioned aero-flotation device which, preferably, comprises a column filled with a liquid, such as water, through which the gas is circulated prior to its injection into the chamber at the bottom of the container, so that it is hydrated, since it is converted into gas with a high moisture content or the other types of liquids described above.

[0035] In one embodiment, at the bottom of the liquid column, where the end of the gas inlet duct is inserted into the same, the incorporation of a filter is provided to generate micro gas bubbles that, when they rise, capture micro-droplets of liquid, altering their composition, such as increasing their moisture content and directing the gas towards the container.

[0036] There are gases other than air that can be used to carry out the invention. Inert gases, without having the capacity to react thermodynamically or electrochemically with the part, such as nitrogen (N), argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), carbon dioxide (CO2) or any combination thereof, can be used.

[0037] It is possible to use other types of gases that have a high convective capacity, in combination with properties such as viscosity, vapor pressure or heat capacity, although they may react with the particles or the part to be treated; such as acetylene, hydrogen sulfide, ammonia, carbonic anhydride, sulfurous anhydride, ethane, ethylene, isobutane, methane, nitric oxide, nitrous oxide, oxygen, propane, etc.

[0038] In some embodiments, such as those described above, in which work is carried out with different gases or with different liquids suspended in the gases, work is carried out in a sealed chamber and in a controlled atmosphere. The different partial pressures, moisture, vapor pressure, and dew point temperature of the atmosphere, among other thermodynamic properties, can be modified in order to obtain better control or stability of the chemical conditions in which the particles are located.DESCRIPTION OF THE DRAWINGS

[0039] To complement the description being made and to make the features of the invention more readily understandable, drawings are attached to the present specification as an integral part thereof, in which the following is depicted in an illustrative and non-limiting manner.

[0040] FIG. 1 shows a schematic top plan view of a container used in a polishing process by means of solid particles, in which an example of an aero-flotation device comprising equipment for controlling the temperature of the solid particles. In FIG. 1 the container is shown incorporated in an outer cooling jacket.

[0041] FIGS. 2-A and 2-B show respective section views according to the section A-A indicated in FIG. 1, of a container with an aero-flotation device, represented in the rest phase and in operating phase, respectively.

[0042] FIG. 3 shows a schematic perspective view of an example aero-flotation device.

[0043] FIG. 4 shows a schematic perspective view of an example chamber of the aero-flotation device shown in FIG. 3.

[0044] FIG. 5 shows a schematic perspective view of an example network of gas channels of the aero-flotation device shown in FIG. 3, the network of gas channels being configured to be incorporated inside the chamber of FIG. 4.

[0045] FIG. 6 shows a schematic perspective view of an example membrane of the aero-flotation device shown in FIG. 3, the membrane being configured to close the top of the chamber of FIG. 4.

[0046] FIGS. 7-A and 7-B show respective schematic and section views of an example hydration device for suspending micro-droplets of liquid in the gas, represented in the rest phase and in the operating phase, respectively.EMBODIMENTS OF THE INVENTION

[0047] In view of the aforementioned figures, and in accordance with the numbering adopted, a non-limiting exemplary embodiment of the equipment for controlling the temperature of particles in polishing processes by means of solid particles of the invention is shown, which comprises what is described in detail below.

[0048] As shown in the figures, the equipment under consideration, particularly applicable to polishing processes by means of solid particles and / or solid particles with an electrolyte inside a container (1), comprises means for injecting gas (3), such as air, from the bottom of the container (1). More specifically, in one embodiment, the gas injection means (3) comprise at least an aero-flotation device (4) which, in turn, comprises a chamber (40) suitable to fit in the bottom of the container (1), a gas blowing manifold (41), incorporated inside the chamber and connected to a gas inlet duct (42), and a membrane (43) that closes the chamber (40) at the top so that, when filled with pressurized gas, it generates a cushion of gas throughout the base or bottom of the container (1) that, when passing through the membrane (43), rises in the form of homogeneous chambers of gas (8), thermally adjusting the particle content and their environment (2) in the container (1), as shown in FIGS. 2-A and 2-B.

[0049] In one embodiment, as shown in FIG. 4, the chamber (40) of the aero-flotation device (4) has a lower base (400) with a perimeter partition (401) that, as a support ring, adapts to the shape of the bottom of the container (1), for example circular, and defines a central housing (402) for accommodating the blowing manifold (41), the assembly being closed at the top by the membrane (43).

[0050] In a one embodiment, the chamber (40) is a part made of PVC, although other non-conductive or conductive materials may be used. The use of a non-conductive material is preferred.

[0051] Preferably, as shown in FIG. 5, the blowing manifold (41) is formed by a circuit of micro-perforated rubber tubes (410) that, joined together by means of two or three-way interconnections (411), form a perimeter frame, where one of said interconnections (411) connects to the gas inlet duct (42), and several central branches with closed distal ends, so that the gas only emerges through the micro-perforations. Said perforations have a diameter measuring between 10 μm and 10 mm, preferably between 100 μm and 2 mm, more preferably between 500 μm and 1 mm. The gas entering through the inlet duct (42) is injected under pressure from a gas compressor not represented.

[0052] Furthermore, the membrane (43) that closes the chamber (40) at the top is preferably an AISIS 316 fine mesh of 100 μm on a support made of plastic material, for example, PVC (polyvinyl chloride) or PVDF (polyvinylidene fluoride), or made of rubber material, such as NBR (nitrile butadiene rubber).

[0053] FIGS. 7-A and 7-B show how, in one embodiment, the equipment of the invention further comprises a hydration device (5) to increase the moisture in the compressed gas (3) prior to it being injected into the aero-flotation device (4). A possible hydration device (5) comprises, for example, a column (50), which defines a container closed at the top with a lid (51) and which is filled with some liquid, preferably water, through which gas (8), preferably air, is circulated through a gas inlet tube (52), which outlet mouth (520), or outlet opening of the dry gas (8), is located at the bottom of the column (50), and a gas outlet tube (53), which inlet mouth (530), or inlet opening of the hydrated gas (8″), is located at the top of the column (50), above the liquid level.

[0054] Thus, the gas once moistened (8′) is injected from the outlet tube (53), once connected to the inlet duct (42), towards the aero-flotation device (4).

[0055] In one embodiment, at the outlet mouth (520) of the inlet tube (52) of non-moistened gas (3) at the bottom of the column (50) with the liquid, the incorporation of a filter (54) is provided to generate micro bubbles.

[0056] Optionally, the container (1), as shown in FIGS. 1 and 2-A, 2-B, is incorporated inside a cooling jacket (6) that surrounds it externally and has a cooling fluid inlet (61) at the bottom and a cooling fluid outlet (62) at the top.

[0057] Having sufficiently described the nature of the present invention, as well as how to implement it, it is not considered necessary to further explain it so that any person skilled in the art can understand its scope and the advantages derived from it.

Claims

1. A method for surface treating a metal part through ion transport using electrically conductive solid particles, the method comprising:electrically coupling the electrically conductive solid particles to a first pole of a current generator, the solid particles being located within an interstitial medium inside a container;electrically coupling the surface of the metal part to a second pole of the current generator;causing friction between the surface of the metal part and the solid particles;altering a temperature of the solid particles by injecting a gas into the container such that the gas circulates in the interstitial medium and between the solid particles inside the container.

2. The method of claim 1, wherein the solid particles are loaded with an electrolyte.

3. The method of claim 1, wherein the altering of the temperature of the solid particles by injecting a gas into the container occurs during the surface treating of the metal part.

4. The method of claim 1, wherein the circulating gas is air.

5. The method of claim 1, wherein the gas injected into the container has a temperature below a temperature of the interstitial medium.

6. The method of claim 1, wherein the gas injected into the container has a temperature below a temperature of the solid particles.

7. The method of claim 1, wherein the gas is injected into the container from a lower part or a bottom of the container.

8. The method of claim 7, wherein the gas is injected into the container by an aero-flotation device.

9. The method of claim 1, further comprising suspending micro-droplets of a liquid within the circulating gas.

10. The method of claim 9, wherein the suspending micro-droplets of a liquid within the circulating gas comprises spraying polar liquid into the circulating gas.

11. The method of claim 10, wherein the spraying of polar liquid is carried out by one or more injectors located inside the container.

12. The method of claim 1, further comprising hydrating the gas prior to the gas being injected into the container.

13. Equipment for surface treating a metal part through ion transport by use of electrically conductive solid particles located within an interstitial medium inside a container, the equipment comprising means to circulate a gas originating from outside the container into the interstitial medium and between the solid particles inside the container.

14. The equipment of claim 13, wherein the means for circulating a gas comprises at least one aero-flotation device that comprises:a chamber located at or near a bottom of the container;a gas blowing manifold that includes one or more perforated tubes incorporated inside the chamber and connected to a gas inlet duct; anda fine mesh membrane that closes a top of the chamber;the aero-flotation device being configured to generate a cushion of gas above the membrane upon a pressurized gas being introduced into the gas inlet duct.

15. The equipment of claim 14, wherein the chamber has a lower base with a perimeter partition that functions as a support ring and adapts to the shape of the bottom of the container, and defines a central housing for accommodating the blowing manifold.

16. The equipment of claim 14, wherein the chamber is made of a material that is not electrically conductive.

17. The equipment of claim 13, further comprising a hydration device configured to incorporate micro-droplets of a liquid into the gas prior to the gas being circulated through the interstitial medium and between the solid particles inside the container.

18. The equipment of claim 17, wherein the hydration device comprises:a column filled with the liquid;a gas inlet tube that includes an outlet mouth located in a lower part of the column; anda gas outlet tube that includes an inlet mouth located at an upper part of the column, above the liquid level.

19. The equipment of claim 18, wherein the outlet mouth of the inlet tube includes a filter.

20. The equipment of claim 13, wherein the container is incorporated inside a cooling jacket that includes a cooling fluid inlet and a cooling fluid outlet.

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