Patent Description:
Many industrial applications require the use of discrete, well-defined and uniform coatings applied to predetermined areas. Conformal coating material is used to protect selected components of a circuit board from moisture, dirt, etc. Such coatings are very useful in varied processes, such as conformal coatings on non-uniform or irregular substrates like electronic circuit boards. It is desirable to obtain broad, uniform coatings using a non-contact applicator with sharp, square, cut-on and cut-off edges.

The conformal coating material typically includes a solvent. During the application and curing of the conformal coating material, the solvent evaporates into the closed environment of the coating system and/or curing oven. Exceedingly high levels of solvent pose an increased fire risk and, as such, the evaporated solvent needs to be removed from the system to allow for uninterrupted operation of the system.

Current systems require continuous extraction levels above a preset threshold to avoid reaching a dangerous solvent concentration. This level is often determined based on worst-case evaporation calculations. However, continuous extraction at the same level is energy inefficient. Therefore, there is a need for improved systems and methods for detecting the level of evaporated solvent in the system and for removing excess evaporated solvent in an efficient manner.

A system and a method for venting a solvent in accordance with the prior art is known from <CIT>.

Systems and methods for venting a solvent are disclosed. A system according to the invention is defined in claim <NUM> and a method according to the invention is defined in claim <NUM>.

Aspects of the disclosure will now be described in detail with reference to the drawings, wherein like reference numbers refer to like elements throughout, unless specified otherwise.

Systems and methods are disclosed for efficiently removing evaporated solvent from a coating system, such as a conformal coating system. A system for applying a conformal coating onto a substrate, such as a printed circuit board, may include an applicator that deposits the conformal coating onto the substrate, and an oven that can heat treat the coated substrate. After the conformal coating is applied to the substrate, the substrate may be moved to the oven for treatment. Alternatively, the applicator and the oven may be housed together. In some embodiments, the coating may contain volatile compounds, such as solvents, that are maintained at a safe concentration within the applicator, oven, or both.

A system <NUM> for curing a coating material may include an oven <NUM> and a coating assembly <NUM>. The coating assembly <NUM> has a coating material source <NUM> and an applicator <NUM>. Referring to <FIG>, the oven has an interior volume <NUM> and one or more heating zones <NUM>. Each heating zone <NUM> receives the coated substrate <NUM> and heats the environment within the heating zone <NUM> to a predetermined temperature. The substrate may be moved on a conveyer belt. In one embodiment, each heating zone <NUM> may be an enclosure that is separated from the rest of the oven by physical borders or dividers. In another embodiment, with specific reference to the illustrative embodiment in <FIG>, each heating zone <NUM> may be a region of the oven <NUM> that is not physically divided from the rest of the oven. In some embodiments, the heating zone <NUM> may be defined by the interior volume <NUM> of the oven, such that the heating zone <NUM> is in fluid communication with the interior volume <NUM>.

The temperature in each heating zone <NUM> may be fixed, or it may be adjusted during the heating process. The transition between one heating zone and an adjacent heating zone may be gradual and may include a temperature gradient ranging from the temperature of the first heating zone to the temperature of the second heating zone. In some embodiments, part of the interior volume <NUM> that defines a first heating zone <NUM> may also define a second heating zone <NUM>, such that the heating zones <NUM> overlap.

The system <NUM> also includes a vent <NUM>. The vent <NUM> is connected to the oven <NUM> to allow movement of gases, such as evaporated solvent, inside the oven <NUM> to an environment external to the oven <NUM>. The vent <NUM> includes an opening that defines a passage <NUM> between the interior volume <NUM> of the oven <NUM> and the environment external to the oven <NUM> and, specifically between the heating zone <NUM> and the environment external to the oven <NUM>. In some embodiments, a single vent may be accessible to the plurality of heating zones <NUM>, such that evaporated solvent in any of the plurality of heating zones <NUM> may be moved to the environment external to the oven <NUM>. Alternatively, the oven <NUM> may include a plurality of vents <NUM>, wherein each vent defines a separate passage <NUM> between the interior volume <NUM> and the environment external to the oven <NUM>.

The vent <NUM> has a regulator <NUM> that can be adjusted to vary the rate at which evaporated solvent can flow from the interior volume <NUM> of the oven <NUM> to the environment external to the oven <NUM>. The regulator <NUM> is positioned adjacent the interior volume <NUM> of the oven <NUM>, inside the passage <NUM> defined by the vent <NUM>. In some embodiments, the vent <NUM> may include multiple regulators <NUM> located in the same or in different locations within or adjacent to the vent <NUM>. A regulator <NUM> may include a baffle, a gate, a valve, or another suitable device that can be adjusted to permit or block the passage of the evaporated solvent.

In some embodiments, the regulator <NUM> has an open configuration, a partially open configuration, and a closed configuration. In the open and partially open configurations, the passage <NUM> is substantially unobstructed, and the evaporated solvent can move through the passage in the vent. In the closed configuration, the passage <NUM> is substantially blocked such that the evaporated solvent is blocked within the interior volume <NUM> of the oven <NUM>. In the partially open configuration, the passage <NUM> is obstructed more than in the open configuration but less than in the closed configuration, to allow for intermediate flow of the evaporated solvent.

Referring to <FIG>, the regulator <NUM> may be a vent gate 206a configured to rotate to partially or completely open the regulator <NUM>. The vent gate 206a may have one movable portion or it may have multiple movable portions, as shown in <FIG>. In another embodiment shown in <FIG>, the regulator <NUM> may be a hinged lid 206b positioned on top of the vent <NUM>. The hinged lid 206b swings away from the vent into the open configuration, and returns to cover the vent <NUM> in the closed configuration. When closed, the hinged lid 206b substantially seals the vent <NUM> such that the evaporated solvent is blocked within the interior volume <NUM> of the oven <NUM>.

Referring to <FIG>, the system <NUM> includes a fan <NUM> used to create a negative pressure in the interior volume <NUM> of the oven <NUM>. The fan <NUM> may be positioned within the interior volume <NUM> of the oven <NUM>, within the vent <NUM> as shown in <FIG>, or external to the oven <NUM> as shown in <FIG>. In some embodiments, the system may include multiple fans.

In some embodiments, the fan <NUM> may be disposed within or on a vent <NUM> extending from the coating assembly <NUM>. In other embodiments, the fan <NUM> may be disposed in another portion of the system, such as a HVAC unit in fluid communication with the vent <NUM>. For example, the system <NUM> may be kept inside a closed environment, such as an enclosure <NUM>, and the fan <NUM> may be disposed on a vent <NUM> that connects the inside of the closed environment with the outside environment.

The fan <NUM> and/or regulator <NUM> may be actuated manually by a user, or they may be configured to automatically actuate in response to a program. For example, the evaporated solvent needs to be removed from the system <NUM> as the quantity of the evaporated solvent reaches a threshold level. As such, referring to <FIG>, the system may include a sensor <NUM> that quantifies how much evaporated solvent is inside a closed volume, such as in the coating assembly <NUM> (sensor 210a) or in the interior volume <NUM> of the oven <NUM> (sensor 210b). The system <NUM> may have multiple sensors <NUM> disposed in different volumes of the system.

The sensor <NUM> is a solvent sensor that is configured to detect the quantity of the evaporated solvent of a solvent. The sensor <NUM> can provide real-time levels of evaporated solvent to a controller <NUM>, such as a computer or server, for the generation of alerts or signals to control extraction of the evaporated solvent. The controller <NUM> may be located on the applicator <NUM> or may be external to the system <NUM>. The controller <NUM> may be physically detached from the system <NUM> while maintaining a functional connection to the sensor <NUM> (for example, through wireless means). For example, when a predetermined threshold concentration of evaporated solvent is detected, the suction may be increased by adjusting the speed of the fan <NUM>, adjusting the regulator <NUM> to a partial or completely open position, or by adjusting the HVAC system. Alternatively, if the concentration of evaporated solvent is greater than the predetermined threshold, the system may be shut down.

In some embodiments, the system <NUM> may include a flow meter <NUM> within the coating assembly <NUM>. Referring to <FIG>, the applicator <NUM> may be in fluid communication with a coating source <NUM> and is configured to move coating material (not shown) from the coating source <NUM> for application onto a substrate <NUM>. The amount of coating material moved through the applicator <NUM> to the substrate <NUM> may be quantified with a flow meter <NUM>. In some embodiments, the flow meter <NUM> may be disposed on the applicator <NUM>, for example on the tip <NUM> of the applicator <NUM>, such that it can measure how much coating material passes from the applicator to the substrate. In another embodiment, the flow meter <NUM> may be disposed at the coating material source <NUM> or between the source and the applicator, such that the flow meter <NUM> can quantify the amount of coating material that passes from the source to the applicator. In some embodiments, the flow meter <NUM> may measure the displacement of the coating material within the coating material source <NUM> or the applicator <NUM>. Some systems may have a plurality of flow meters <NUM> positioned at multiple locations within the coating assembly <NUM>.

The flow meter <NUM> can measure one or more parameters of the flow of the coating material. In some embodiments, flow meter <NUM> may measure the volume, the velocity, or the pressure, and/or the duration of the flow. The flow meter <NUM> may be connected to a controller <NUM> configured to receive data from the flow meter <NUM> and perform analysis on the data. The controller <NUM> may also be configured to analyze other parameters of the flow, such as the type of coating material, the characteristics of the applicator <NUM> and/or the oven <NUM>.

In some embodiments, the system <NUM> may include an oven <NUM> or a coating assembly <NUM> as described herein. It will be understood that a system having an oven may interact with a system having a coating assembly, and this disclosure contemplates systems that have either an oven <NUM> or a coating assembly <NUM>, as well as systems that have both an oven <NUM> and a coating assembly <NUM>.

In operation, the system <NUM> may include a dynamic feedback system. With reference to <FIG>, a method <NUM> for curing coating material on a substrate <NUM> is described according to one embodiment. Initially, in step <NUM>, the substrate <NUM> coated with a conformal coating is heat cured in the heating zone <NUM>. While the substrate <NUM> is within the oven <NUM>, the solvent sensor <NUM> continuously measures the quantity of evaporated solvent inside the oven in step <NUM>. The solvent sensor <NUM> may measure the solvent at predetermined time increments, once the oven reaches a preset temperature, or according to a program.

In step <NUM>, the controller <NUM> receives the quantity of evaporated solvent from the solvent sensor <NUM> to determine the concentration of evaporated solvent based on the known volume of the heating zone <NUM> and/or interior volume <NUM>. If the concentration of evaporated solvent reaches a predetermined shutdown threshold, the system <NUM> may be configured to shutdown operation in block 408a. If the concentration of evaporated solvent reaches an action threshold, which is lower than the shutdown threshold, the system <NUM> may actuate the fan <NUM> or HVAC system in step 408b or toggle the regulator <NUM> from the closed configuration to the open configuration or semi-open configuration in step 408c to control suction of the evaporated solvent. If the concentration of evaporated solvent is below the action threshold, the system <NUM> may maintain operating conditions without change.

In one embodiment, the shutdown threshold may be an evaporated solvent concentration of <NUM>% of a Lower Flammable Limit. The action threshold is preferably below the shutdown threshold and may range, for example, between <NUM>% and <NUM>% of Lower Flammable Limit to enable the system <NUM> to decrease the evaporated solvent concentration before shutting down. In some embodiments, the method <NUM> may also include a warning threshold triggering an audible or visual alarm, or an electronic notification to one or more users. The warning threshold may be less than the action threshold, between the action threshold and the shutdown threshold, or above the shutdown threshold.

Referring to <FIG>, a method <NUM> is described using multiple thresholds to control the evaporated solvent concentration before shutdown. In step <NUM>, the concentration of evaporated solvent is determined as described above. If the solvent concentration equals or exceeds a first threshold in step <NUM>, the system <NUM> may toggle the regulator <NUM> from a closed position to a semi-open or to an open position to open the passage <NUM> of vent <NUM>. The open passage <NUM> permits the evaporated solvent to passively move out of the system, or allows air from the HVAC system to enter or exit the volume. If the concentration of solvent then reaches a second threshold that is higher than the first threshold in step <NUM>, the system may actuate the fan <NUM> to actively move the evaporated solvent through the vent <NUM> by turning on the fan <NUM> or increasing the speed of the fan <NUM>. If the evaporated solvent concentration continues to a third, shutdown threshold, the system may be configured to shut down.

The system <NUM> may utilize a flow meter <NUM> or a timer that measures the time the coating material is applied to the substrate <NUM> to estimate the concentration of evaporated solvent. With reference to <FIG>, a method <NUM> for estimating the concentration of evaporated solvent using a flow meter or timer is described. In step <NUM>, coating material is applied to the substrate. In step <NUM>, the flow meter <NUM> measures the quantity of coating material applied to the substrate <NUM> or a timer measure the amount of time that the applicator tip <NUM> is applying the coating material. As described above, the flow meter <NUM> may be disposed at different positions between the coating material source <NUM> and the substrate <NUM>. Without using the flow meter <NUM>, the flow rate of the coating material may be known and multiplied by the time that the applicator tip <NUM> is applying the coating material.

The system <NUM> and/or controller <NUM> also stores additional parameters to estimate the concentration of evaporated solvent in step <NUM>, as described above. In step <NUM>, the system determines whether the estimated concentration of evaporated solvent is greater than or equal to a predetermined threshold, such as the alert threshold, the action threshold, or the shutdown threshold. If the estimated concentration is higher, the system <NUM> may decrease the evaporated solvent concentration or shut down in step <NUM>.

Various modifications or additions to the system <NUM> are contemplated. For example, the system <NUM> may include a filter and/or a scrubber (not shown) such that the evaporated solvent that passes through the vent <NUM> is filtered or scrubbed before being released to the environment according local emission regulations. The substrate <NUM> may alternatively be cured via gas convection or via application of radiation, such as infrared, ultraviolet, or visible radiation.

System <NUM> may also include a transport element <NUM> that transfers the substrate from the coating system to the oven. The transport element may include a conveyor, an inverter or flipper, or another suitable structural feature that is configured to move the substrate through the system. The transfer element <NUM> may be disposed between the coating system and the oven, or it may be disposed within the coating system or the oven. Multiple transfer elements <NUM> may be present in the system, for example adjacent each of the coating system and the oven, such that the multiple transfer elements <NUM> may be positioned adjacent one another to move the substrate from the coating system to the oven and/or out of the oven.

In some embodiments, the transport element may include a solvent sensor <NUM> that can be configured to sense and/or quantify the evaporated solvent and to send a signal to another element of the system. Referring to <FIG>, the transport system <NUM> may be disposed between the coating assembly <NUM> and the oven <NUM> and may include a solvent sensor 210c.

The embodiments disclosed herein offer a number of advantages. Utilizing a solvent sensor to monitor the evaporated solvent concentration or a flow meter to estimate the evaporated solvent concentration enables for dynamic evaporated solvent removal. Such dynamic evaporated solvent removal decreases the fire and/or explosions risks associated with high levels of evaporated solvent, and minimizes the need for a system shutdown to improve system efficiency. In addition, by only removing evaporated solvent as necessary, energy costs associated removal of the evaporated solvent, including energy costs for cooling air fed into the system <NUM>, are reduced.

While the present disclosure depicts exemplary implementations related to application and curing of conformal coatings, it will be understood that the embodiments disclosed throughout this application may be utilized in a variety of other industrial applications. Similar advantages may be appreciated by incorporating one or more of the above embodiments in liquid painting systems for curing paint coatings or for applying coatings to cans or other containers.

For example, <FIG> shows an illustrative embodiment of a system <NUM> for applying liquid paint to drums <NUM>. The system <NUM> has a housing <NUM>, inside which liquid paint is applied to the drums <NUM>. The housing <NUM> may include a vent <NUM> defining a passage <NUM> extending between the interior of the housing <NUM> and the exterior of the housing <NUM>. The system <NUM> may further include one or more sensors <NUM> for quantifying one or more parameters within the system <NUM>. In some embodiments, the system <NUM> may include a flow meter <NUM> to quantify the amount of material applied to the drums <NUM>. The operation of the vents <NUM>, the sensors <NUM>, and the flow meters <NUM> is described throughout this application and may be applied to system <NUM> as well.

Referring to <FIG>, a system <NUM> is shown for applying a paint or coating to beverage containers (e.g. aluminum cans <NUM>). The system <NUM> has a housing <NUM>, inside which the coating and/or paint is applied to the cans <NUM>. The housing <NUM> may include a vent <NUM> defining a passage <NUM> extending between the interior of the housing <NUM> and the exterior of the housing <NUM>. The system <NUM> may further include one or more sensors <NUM> for quantifying one or more parameters within the system <NUM>. In some embodiments, the system <NUM> may include a flow meter <NUM> to quantify the amount of material applied to the cans <NUM>. The operation of the vents <NUM>, the sensors <NUM>, and the flow meters <NUM> is described throughout this application and may be applied to system <NUM> as well.

Claim 1:
A system (<NUM>) for venting a solvent, the system comprising:
an oven (<NUM>) having an interior volume (<NUM>) defining a heating zone (<NUM>), the interior volume (<NUM>) for receiving at least one substrate (<NUM>) coated with a coating material comprising a solvent;
a vent (<NUM>) coupled to the oven (<NUM>), the vent (<NUM>) defining a passage (<NUM>) between the interior volume (<NUM>) and an environment external to the oven (<NUM>) and having a regulator (<NUM>) that can be adjusted to vary a rate at which evaporated solvent can flow from the interior volume (<NUM>) of the oven (<NUM>) to the environment external to the oven (<NUM>), wherein the regulator (<NUM>) is positioned adjacent the interior volume (<NUM>) of the oven (<NUM>), inside the passage (<NUM>) defined by the vent (<NUM>),
a solvent sensor (<NUM>) at least partially located in the interior volume (<NUM>) and configured to measure an amount of the evaporated solvent present in the interior volume (<NUM>);
a fan (<NUM>) in fluid communication with the passage (<NUM>) and configured to remove at least a portion of the evaporated solvent from the interior volume (<NUM>),
characterised in that a speed of the fan (<NUM>) is controlled based on the measured amount of the evaporated solvent present in the interior volume (<NUM>),
wherein, if an evaporated solvent concentration equals or exceeds a first threshold, the system (<NUM>) toggles the regulator (<NUM>) from a closed configuration to a semi-open configuration to open the passage (<NUM>) of the vent (<NUM>),
wherein, if the evaporated solvent concentration then reaches a second threshold that is higher than the first threshold, the system (<NUM>) actuates the fan (<NUM>) to actively move the evaporated solvent through the vent (<NUM>) by turning on the fan (<NUM>) or increasing the speed of the fan (<NUM>), and
wherein, if the evaporated solvent concentration continues to a third, shutdown threshold that is higher than the second threshold, the system (<NUM>) is configured to shut down.