Device to prevent moisture from being absorbed from the soldering flux contained in a big bag® up to the soldering head

Abstract

Compact device for preventing moisture absorption of welding flux contained in a big bag® until its introduction into the hot air transport network, characterized by: - ​​an inflatable sleeve (A) inserted at the outlet of the big bag® and connected to a pipe that transports the flux to the distribution box, - the welding flux delivery pipe receives: ° A first vibrator (D) on the supply pipe which loosens the flux inside the pipe, ° a sealed valve (B) placed more or less in the middle of the pipe, which releases the flux from the big bag, ° A control mechanism (H) connected to a level sensor (G) which triggers the opening of the valve, ° A loosening grid (F) coupled to a second vibrator (E) which continuously feeds the flux box with a fine mist of powder. Figure for the abbreviation [Fig 1].

Description

Title of the invention: Device for preventing moisture absorption in soldering flux

[0001] The invention relates to a system for preventing the reabsorption of moisture from the soldering flux during transport from the big bag (oven-dried by the manufacturer and used cold) to the soldering head. The released flux is then heated according to a technological principle similar to the device for transporting soldering flux to the soldering head without moisture reabsorption, which was the subject of a patent application under No. FR2312240. The difficulty encountered in this new configuration of soldering flux distribution by big bag® is that the flux is not reprocessed on-site, but purchased in big bags® in a new (and therefore dry) but cold state. This leads to a problem: when the flux is released from the big bag®, it forms clumps that cool the air and create a risk of moisture reabsorption. Two problems arise:

[0002] The first point is that the compaction of the flux depends on its physical nature (particle size, shape of components, different materials, etc.), and there are many fluxes that behave differently in terms of compaction. It was therefore necessary to ensure a technological solution capable of satisfying the topology of compaction formation according to the physical nature of the fluxes (composition). Flux manufacturers provide no information in this regard.

[0003] A second problem arose concerning the need to heat the stream to a temperature above 100°C, the temperature below which moisture reabsorption is possible. While the device described in patent no. FR2312240 avoids cooling and therefore prevents moisture reabsorption in a hot steamed stream (released immediately in a hot state), this device becomes ineffective with a cold stream.

[0004] State of knowledge: It is appropriate to mention the various known technological devices that come closest to the present object, and to recall the scientific laws that govern both the physical nature of the welding flux and the absorption of moisture.

[0005] From a technological standpoint, it is necessary to distinguish three types of known technologies in the field of flow transport:

[0006] The first concerns conventional devices such as those developed by the companies "ESAB®" and "Lincoln Electric®": which have developed a technology based on the principle of pushing welding flux without worrying about moisture absorption during transport, see below the figure of the device marketed by Esab®. Note that the latter (like that of Lincoln Electric®) dispenses to address the issue of moisture reabsorption, the devices only serve to transport the flow to its destination.

[0007] Next, it is necessary to recall the device for transferring the welding flux from the oven to the welding head, as introduced by the present applicant in a first device, "Cerf," which was the subject of patent No. FR1501661. This device is characterized by: -Guillotine valves (a and c) which ensure the opening of the curing and storage modules in a precise order towards the transfer box, - A network of tubes (b) that links the guillotine valves (a and c) and supplies the transfer box (j), - A transfer box (j) inclined at 45° C to prevent the flux from remaining in the box, - A controller (m) with special programming collecting information from both the welding head and the curing and storage modules, synchronizing the opening and closing actions of the hatches and the air intake from the turbine, regulating the opening times of the valves (a and c) and blower according to the length of the flux supply pipes to the welding head, the elevation difference and the flow rate of the flux to the welding head.

[0008] Furthermore, each guillotine valve (a and c) of the transport module was composed of: a feed tube (h) in the upper part, a support plate (d) of the casing fixed to the feed tube (h), the pouring funnel (o) which distributes the released welding flux, a second connecting tube (f) placed between the feed tube (h) and the guillotine (i) to manage thermal expansion and contribute to the air and dust tightness of the valve, a compression seal (e) positioned between the support plate (d) and the connecting tube (f) in order to ensure a perfect seal, and a guillotine (i).

[0009] This technology does not solve the problem of moisture reabsorption, since the only requirement of the patent relates to the temperature of the flux during transport to the welding head, without the issue of moisture reabsorption during this transport being managed.

[0010] The third known technological device is patent application No. FR2312240 filed by our company, based on the principle of maintaining the temperature of the solder flux above 100°C during its transport, using the prior storage of the solder flux in ovens (the subject of the Cerf® device). Let us recall the principles of this Cerf® patent, which is characterized by the fact that this device for transporting reprocessed solder flux guarantees compliance with welding standards in a nuclear environment, in particular by preventing moisture absorption during transport from the oven to the welding head. This device is governed by the principle of maintaining a flux temperature of at least 100°C during said transport. The purpose is to phase-shift the moisture in the flow. The device developed in 2022 is mechanically identical to the one described in French patent FR 1501661. However, this new device differs from the one described in French patent FR 1501661 in that it is characterized by: - an air heater (a) placed upstream of the transfer box (index J of patent FR1501661), heater equipped with a control system (b) and a temperature probe (c) at the inlet of the flow distribution box, - a second sub-assembly provided with insulation (g) and a heating cable (h) over the entire length of the piping between the flow distribution box and the head hopper (e), a temperature probe (d) at the inlet of the head hopper (e), and a control system (f) controlled by the temperature probe (d), - a third sub-assembly consisting of a motorized fresh air intake valve (k) at the inlet of the filter (j) associated with a control system (1) controlled by a temperature probe (i) at the inlet of the filter (j).

[0011] The problem posed with regard to the subject matter of the present patent is that this latter technology FR2312240, while relevant on hot solder flux, cannot be applicable in the case of solder flux released at room temperature.

[0012] From a scientific point of view, two subjects are relevant to our field of investigation, namely: Carrier's law and the physical nature of powders.

[0013] Carrier's Law refers to the "Carrier" diagram. This diagram allows us to understand the laws governing the evolution of air humidity as a function of temperature. Note in this diagram the concept of relative humidity (indicated as a percentage of volume), while the concept of absolute humidity is expressed in grams of water per kg of dry air:

[0014] Absolute humidity: The absolute humidity of an air mass represents the quantity in grams of water vapor [g vapor / kg dry air] present in a given volume of dry air (lm3), and its value remains constant even if the air temperature varies, provided it remains above the dew point temperature (the dew point temperature is the temperature at which the water vapor contained in the air begins to condense). The vapor contained in an air mass is invisible, but if dry air becomes saturated with humidity beyond a certain limit, fog and condensation appear; the water then forms droplets suspended in the air, and the air is said to be saturated.

[0015] Relative humidity: Relative humidity (RH) is expressed as a percentage (%) and corresponds to the ratio between the amount of water contained in the air (absolute humidity) and the maximum amount it can hold at a given temperature before condensation. Temperature variations directly influence relative humidity. so that relative humidity decreases when the temperature rises and increases when the temperature falls.

[0016] According to Carrier's law diagram, in order to reduce the amount of water contained in the material (here, the welding flux), it is necessary to: cool the air to a temperature below its dew point, then condense the water vapor present in the air, which is then separated from the air. Under these conditions, the cooled, dried air must be reheated to return to its initial temperature.

[0017] Regarding the physical behavior of welding flux: These fluxes exhibit very different physical behaviors (temperature resistance, temperature variation within the same mass due to their composition, particularly their particle size, abrasion, transport capacity, and varying degrees of fragility) depending on their composition, which constrains the design of the equipment that processes them. However, to ensure weld quality, they must be composed of a set of small particle sizes combined with fines. Furthermore, since these welding fluxes are composed differently, their gravitational properties vary considerably depending on the flux formulation. These different characteristics limit our scope of study, as it is necessary to both: - to bring these transported welding fluxes to a temperature of over 100°C during transport from the big bag® to the welding head hopper, in order to prevent moisture absorption during transport, - release the flow regularly to ensure consistent heating capable of releasing the flow at over 100°C and thereby preventing any moisture reabsorption.

[0018] However, there is a constant pattern of behavior observed, on three points:

[0019] The first point is that all soldering fluxes are highly absorbent, and this is especially true of agglomerated fluxes, which are the most commonly used. It is therefore important that the equipment used to handle them during processing, storage, or transport does not allow for any absorption of moisture.

[0020] They also have a thermal insulation property which considerably constrains the homogeneity of the temperature treatment, in that this property prevents the diffusion of temperature in the mass of flux to be treated.

[0021] They slope at 45 degrees, which also constrains the design of the equipment, both in its thermal design (locations and temperature loads, dimensions of mechanical equipment), and for a perfect flow without residual flux remaining in the equipment.

[0022] All of this knowledge does not enable a person skilled in the art to solve a device capable of preventing the reabsorption of moisture from the welding flux at ambient temperature during the transport of the big bag® to a welding head.

[0023] Presentation of the invention: The invention relates to a compact device for preventing the reabsorption of moisture from welding flux contained in a big bag® until its introduction into the hot air transport network, a network identified in patents FR1501661 and, more specifically, in its latest developments, by patent FR2312240. The device is characterized by the latter patent in its connection between the big bag® containing the welding flux and the distribution box (C), as described in the previous patents. This connection is characterized by: - an inflatable sleeve (A) inserted at the outlet of the big bag® and connected to a pipe that carries the flux to the distribution box, this inflatable sleeve being designed to ensure airtightness, - the welding flux drain pipe receives: ° A first vibrator (D) on the supply tubing to prevent clogging and to loosen the flow inside the tubing, ° a sealed valve (B) placed more or less in the middle of the tubing, which releases the flow from the big bag, ° A control system (H) connected to a level sensor (G) which triggers the opening of the valve according to the principle that if there is no flow present in the tubing at the location of the sensor, the control system opens the sealed valve, ° A decompaction grid (F) coupled to a second vibrator (E) which continuously feeds the flow box with a fine spray of powder - in order to constitute a continuous cloud of powder (and not masses of released flux) allowing the hot air flow contained in the transport system indicated in patent FR2312240 not to be cooled.

[0024] The invention is based on the principle of a continuous supply of welding flux in a cloud of powders, as opposed to a supply of flux by bulk masses. Thus, the introduction of the powders into the hot air transport system to the welding head ensures a temperature greater than or equal to 100°C inside the hot air circuit, thereby preventing moisture absorption. It should be noted that this is a requirement in the regulations for nuclear equipment.

[0025] Preferably, this device can be introduced into a compact assembly with the technology of invention patent FR2312240, and will be used for small maintenance and equipment operations, operations requiring compact tools.

[0026] [Fig. 1] General view of the device introduced into the welding flux transport device according to patent application FR2312240.

[0027] Glossary: A) Inflatable cuff, B) Watertight valve, C) Timing box, D) first vibrator, E) second vibrator, F) decompaction grid, G) Level probe, H) Control

Claims

[Claim 1] Demands Compact device for preventing moisture absorption of welding flux contained in a big bag® until its introduction into a hot air transport network, characterized by: - an inflatable sleeve (A) introduced at the outlet of the big bag® and connected to a tube which ensures the transport of the flow to a distribution box, this inflatable sleeve being intended to ensure airtightness against ambient air, - the flux drop tube receives: ° A first vibrator (D) on the supply tubing to prevent clogging and to loosen the flow inside the tubing, ° a watertight valve (B) placed on the tubing, which releases the flow from the big bag, ° A control system (H) connected to a level sensor (G) which triggers the opening of the valve according to the principle that if there is no flow present in the tubing at the location of the sensor, the control system opens the sealed valve, ° A decompaction grid (F) coupled to a second vibrator (E) which continuously feeds a flow box with a fine spray of powder - in order to constitute a continuous cloud of powder (and not masses of released flux) so as not to cool the hot air flow contained in the transport system.

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