Patent Application
20240342744
The present invention relates to a method of applying a coating material to a concave surface of an article, and an application system for use in coating a concave surface of an article with a coating material.
It is known to apply a coating material to a surface of a preform of a base material so that final product (which may be at least the preform with the coating material applied) has properties and/or characteristics that are not possible with the material of the preform alone.
By way of example, it is known to apply a coating of wax to paperboard so that the wax-coated paperboard has a resistance to water. In this example, the wax can be coated by a spray-coating process that broadly involves heating wax to a temperature above its solid-to-liquid transition temperature, and spraying the liquid wax onto the surface of the paperboard. The temperature of the paperboard is below the solid-to-liquid transition temperature of the wax, so that the wax hardens on contact.
Spray-coating processes are beneficial for relatively flat surfaces, where there is minimal variation of the relative positions of the spray nozzles and the target surface during the coating process. This enables the coating material to be applied with a predictable relatively uniform thickness. However, spray-coating processes are less suitable for coating materials onto a curved target surface. To this end, achieving a uniform thickness of a coating material on a target surface that has portions with small radii, and/or varied radii by spray-coating processes is difficult and time-consuming. These difficulties are exacerbated for concave target surfaces. In addition, where only part of a surface of a preform is to be coated, the surface outside of that part must be masked to prevent overspray coating in unwanted regions of the surface.
By way of another example, it is known to apply a coating of wet glaze (typically minerals and metal oxides in an aqueous suspension) onto surfaces of unfired ceramic material. During fired, the glaze solids fuse with one another and with the ceramic material to create an impervious coating on the ceramic material. One method of coating wet glaze involves dipping the ceramic into a bath of the wet glaze. As the ceramic is withdrawn from the bath, excess wet glaze is allowed to flow off the target surface. The rheology of the wet glaze that facilitates this type of dip coating is such that achieving a uniform thickness in the final coating is difficult to obtain. Thus, the result is that in practice coating material is applied to some parts of the target surface in excess, in order to obtain a minimum desired thickness of coating material across the target surface. As will be appreciated, this process leads to wasted application of the coating materials.
A similar coating process for concave surfaces, such as the inner surface of ceramic bowl, involves filling the concavity with the wet glaze, and then tipping/pouring out the excess. Where only a concave surface of a preform is to be coated, the tipping/pouring phase can lead to wet glaze flowing to unwanted regions of the preform surface.
It will be appreciated that spray-coating, dipping and pouring processes can be employed with other coating materials, and also with preforms formed of other base materials.
There is a need to address the above, and/or at least provide a useful alternative.
There is provided a method of applying a coating material to a generally concave surface of an article, the article further having a rim around the concave surface, and a cavity that is defined between the concave surface and the rim, the method involving:
The method can further involve using an application system having a nozzle with a tip end and at least one lumen extending through the nozzle to an opening at the tip end, and
Positioning the nozzle can involve locating the tip end of the nozzle with the opening proximate the concave surface.
In some examples, the method can involve withdrawing the nozzle while simultaneously discharging liquid coating material into the cavity. In some alternative examples, the method involves keeping the nozzle stationary while discharging liquid coating material into the cavity.
Extracting the first amount of the discharged liquid coating material can involve applying a negative pressure differential to the lumen of the nozzle, to thereby draw the first amount of the discharged liquid coating material from the cavity via the nozzle.
Positioning the nozzle can involve positioning the tip end of the nozzle at a predetermined position relative to the concave surface. The predetermined position can be at a predetermined vertical separation from a lowest part of the concave surface having regard to the orientation of the article during the filling and extraction steps, and the nozzle is stationary at the predetermined position while discharging liquid coating material into the cavity, and/or while extracting the first amount of liquid material coating.
In some alternative examples, the nozzles of the application system include a delivery nozzle, and an extraction nozzle that has a tip end and at least one lumen extending through the extraction nozzle to an opening at the tip end, and the method further involves:
Inserting the tip end of the extraction nozzle into the discharged liquid coating material can involve positioning the tip end of the extraction nozzle at a predetermined position relative to the concave surface. The predetermined position can have the tip end of the extraction nozzle at a predetermined vertical separation from a lowest part of the concave surface, having regard to the orientation of the article during the filling and extraction steps.
In some examples, the extraction nozzle is stationary at the predetermined position while extracting the first amount of discharged liquid material coating.
The method can involve inserting the tip end of the extraction nozzle into the discharged liquid coating material to thereby displace coating material upwardly and towards the rim of the cavity. In at least some examples, the method involves discharging a predetermined volume of liquid coating material into the cavity, the predetermined volume being less than the volumetric capacity of the cavity.
In some alternative examples, the step of drawing liquid coating material through the extraction nozzle commences prior to the extraction nozzle arriving at the predetermined position.
In some examples, while discharging liquid coating material into the cavity, the tip end of the delivery nozzle is spaced vertically from the surface level of the discharged liquid coating material. The method can involve withdrawing the delivery nozzle from the cavity while discharging liquid coating material. In some particular instances, while discharging liquid coating material into the cavity, the tip end of the delivery nozzle is positioned at or above the rim of the article.
The method can involve removing the delivery nozzle from the cavity after liquid coating material is discharged into the cavity, and prior to extracting the first amount of liquid coating material from the cavity.
In certain examples, the cavity is to be at least partially filled with a predetermined volume of liquid coating material prior to the extracting step, and the step of discharging liquid coating material into the cavity further involves measuring the volumetric flow of liquid coating material through the nozzle, and controlling the discharge of liquid coating material based on the measured volumetric flow.
In certain other examples, the step of discharging liquid coating material into the cavity involves discharging the liquid coating material for a predetermined period of time.
The application system can include a sensor for sensing the level of the liquid coating material that is within the cavity and relative to a datum associated with one of: the position of the article, or a support bed on which the article is positioned during the discharging step,
The application system can alternatively include a trigger device that has a port, and that in use has two states and is configured to change between those two states in response to the presence of liquid coating material, the port of the device being located at a predetermined position relative to the tip end of the discharge nozzle,
The method can further include a dwell time after liquid coating material is discharged into the cavity, and prior to commencing extraction of the first amount of the liquid coating material,
The application system can include a support bed with one or more location formations, such that the support bed is to support the article with the concave surface facing upward and located in a predetermined position by the location formations, and the method further involves loading the article onto the support bed prior to discharging the liquid coating material into the cavity.
The method can additionally involve applying a locating force to the article to thereby bias the article against the support bed formation.
There is also provided an application system for use in coating a generally concave surface of an article with a coating material, the article further having a rim around the concave surface, and a cavity that is defined between the concave surface and the rim, the application system comprising:
In one example, the coating material transport subsystem further comprises:
The coating material transport subsystem can further comprise:
Preferably, the application system includes:
In some examples, the location formations include concave nesting formations that complement convex surface portions on the underside of the article,
Preferably, the support bed has a datum plane, and the concave nesting formations are located to a lower side of the datum plane,
In some examples, the application system is configured such that when the nozzles are in the deployed position, the nozzles project through the datum plane. Alternatively or additionally, the application system is configured such that when the nozzles are in the deployed position, the tip ends are disposed at a predetermined insertion depth from the datum plane in a direction that is normal to the datum plane. In certain examples, the predetermined insertion depth is adjustable.
The nozzle support chassis can include limit stops that at least partially define the deployed position, and that also limit the movement of the nozzles in away from the elevated position. Preferably, the limit stops are adjustable to enable adjustment of the deployed position.
The support bed and/or nozzle support chassis can include guides that constrain the movement of the nozzle support chassis. Preferably, the guides constrain the movement of the nozzle support chassis in directions that are transverse to the movement of the nozzles between the elevated and deployed positions.
Preferably, the nozzles are mounted on the nozzle support chassis in one or more linear rows.
In certain examples, each nozzle includes at least one discharge lumen that is interconnected with the first flow path, and at least one extraction lumen that is interconnected with the second flow path.
Alternatively or additionally, the coating material transport subsystem can be configured such that at least some of the lumens of each nozzle are interconnected with both the first and second flow paths, whereby liquid coating material can be discharged from, and drawn into the respective lumens.
In some examples, the nozzles include:
In some examples, the nozzles include:
The delivery and extraction nozzles can be mounted on the nozzle support chassis, and arranged such that:
In one arrangement, the delivery nozzle array has a single row of delivery nozzles, and the extraction nozzle array has a single row of extraction nozzles,
Preferably, the row of delivery nozzles is linear, and the row of extraction nozzles forms is linear.
In certain examples, the nozzle support chassis comprises a first frame on which the delivery nozzles are mounted, and a second frame on which the extraction nozzles are mounted,
The application system can further include a support bed translation mechanism that is configured to move the support bed along a process path,
Alternatively or additionally, the support bed translation mechanism is configured to index the support bed along the process path in at least one direction through a set of two or more predetermined positions,
The arrays of delivery nozzles and extraction nozzles can be arranged so that, in use the of the application system, and while the support bed is located at each of the predetermined positions, delivery nozzles are to discharge liquid coating material into the cavities of a group of articles and the extraction nozzles are to draw liquid coating material from the cavities of another distinct group of articles.
Alternatively, the arrays of delivery nozzles and extraction nozzles can be arranged so that, in use the of the application system, and while the support bed is located at each of the predetermined positions, delivery nozzles are to discharge liquid coating material into the cavities of a group of articles and the extraction nozzles are to draw liquid coating material from the cavities of that same group of articles.
In at least some instances, the support bed has an array of concave nesting formations that are arranged in the datum plane into linear rows and columns.
The rows of the array of concave nesting formations are preferably parallel with the rows of the delivery and extraction nozzles.
Preferably, each nozzle is mounted on the nozzle support chassis to align centrally with one of the columns in the array of concave nesting formations.
Nozzles of the application system that are to be at least partially immersed in the liquid coating material (or otherwise inserted into the discharged liquid coating material) while drawing liquid coating material into at least some of the nozzles from externally of the respective nozzle can be constructed to have outer surfaces with a surface energy that is lower than that of the liquid coating material.
The application system can include a support bed temperature management subsystem that enables the temperature of the support bed to be maintained at a predetermined temperature. The predetermined temperature is to be below the liquid-solid phase transition temperature of the coating material. Preferably, the predetermined temperature is adjustable.
The application system can include a locating subsystem to facilitate supporting the article against the concave nesting formations, the locating subsystem being arranged to apply a force against the article when loaded onto the support bed to urge the article into contact with the concave nesting formations.
In one form, the locating subsystem can include clamping system with one or more jaws, wherein the clamping system is configured to clamp a portion of the article between the support bed and the jaws.
Alternatively or additionally, the locating subsystem can include a vacuum system that includes vacuum tubes extending through the support bed and open into the concave nesting formations, wherein the clamping system is configured to draw air from above the concave nesting formations, and thereby apply a suction force against the article.
The coating material transport subsystem includes one or more flowmeters that are configured to measure the flow rate of liquid coating material that is discharged from the respective openings of the nozzles. In at least some examples, the coating material transport subsystem is arranged with one of the flowmeters associated with a respective one of the nozzles to measure the flow rate that is discharged from the opening of that respective nozzle. The coating material transport subsystem can also be configured to measure the flow rate of liquid coating material that is drawn into the nozzles from externally of the nozzles.
The coating material transport subsystem can include one or more sensors for sensing the level of the liquid coating material that is within the cavity of the article and relative to a datum associated with one of: the position of the article on the support bed, the nozzle support chassis, and/or the support bed, wherein the application system is configured to:
Preferably, the sensors use ultrasonic energy, or electro-magnetic energy to sense the level of the liquid coating material. In one form, the sensors can be laser sensors.
The coating material transport subsystem can include a solenoid valve associated with each discharge nozzle, and the application system is configured to close each solenoid valve to thereby cease discharge of liquid coating material from the respective nozzle when the sensed level of liquid coating material reaches the predetermined proximity to the rim of the article into which liquid coating material is discharged from the respective nozzle.
Alternatively or additionally, the coating material transport subsystem can include:
In one example, each trigger device includes a venturi mechanism.
In order that the invention may be more easily understood, embodiments will now be described, by way of example only, with reference to the accompanying drawings, in which:
With respect to this particular example, the coating material applied to the concave surface 3 (the coating is indicated by reference number 9 in
For simplicity in the description that follows, a method of applying a coating material will be described with reference to the blank 1 and/or the vessel 5 (except where the context more suitably refers to an article), and similarly with respect to the application system 10. In an example, the coating material can be a wax, which at typical room temperatures is a solid, and at elevated temperatures changes to a liquid phase. It is known that at least some waxes change from their solid phase to their liquid phase progressively through a range of temperatures. A nominal solid-to-liquid transition temperature is the temperature above which substantially all of the wax is in liquid form. For further simplicity of the description that follows, wax is used as an illustrative example of the coating material.
The application system 10 has a reservoir within which to contain the wax W in a liquid form. The reservoir, which in this example is in the form of a tank 12, has a raw wax feed inlet 14, and a heater 16 and agitator 18 to keep the wax W within the tank 12 in a liquid state and above its solid-to-liquid transition temperature.
The application system 10 includes a support bed 20 with location formations on an upper surface. The location formations are shaped such that in use of the application system 10 the blank 1 locates to a predetermined position on the support bed with the concave surfaces 3 oriented upwardly with respect to the support bed 20.
In the illustrated example, the blank 1 has the general form of a contoured sheet material of approximately constant sheet thickness. The underside of the blank 1 has a convex surface portions that are complementary of the concave surfaces 3. Further, the location formations of the support bed 20 are in the form of concave nesting formations 22 that are evident from
The support bed 20 has a datum plane PD, which in this particular example is coincident with the upper peripheral edges of the concave nesting formations 22. The concave nesting formations 22 are located to a lower side of the datum plane PD.
The application system 10 includes a set of nozzles 24. As indicated in
The tank 12 is in fluid communication with the nozzles 24 via a coating material transport subsystem. As described in further detail below, in use of the application system 10 the coating material transport subsystem delivers liquid wax W from the tank 12 to lumens 28 of some of the nozzles 24 for discharge via the respective openings 30. Further, in use of the application system 10 the coating material transport subsystem draws liquid wax W into some of the nozzles 24 from externally of those respective nozzles 24. Thus, the application system 10 is operable to discharge liquid wax W into the cavities 7 of the blank 1, and extract a first amount of the discharged liquid wax W from the cavities 7, thereby leaving a residual amount of the liquid wax W within those cavities 7.
By filling each cavity 7 with liquid wax W to a level that is at, just below the rim 6, and then extracting some of the discharged liquid wax W back out of the cavity 7, a thin layer of wax W (being the residual amount of liquid wax W) remains on the concave surface 3. By then maintaining the blank 1 with the residual amount of liquid wax W on the concave surface 3 to cool, that residual amount of liquid wax W cures and a coating of solid wax W forms on the concave surface 3.
It will be appreciated that the process described above results in the surface of the web 4 being bare material of the blank 1. This has certain benefits to the final product, and/or benefits to the manufacturer in various factors. With respect to the vessel 5 (which is trimmed from the blank 1 after the wax W is applied by the application system 10), it will be apparent from the description and from
It will also be appreciated that the conditions that are appropriate for the liquid coating material to cure are dependent on the actual coating material, its characteristics, and the nature of the change/transformation that is required to achieve that cure. By way of example, for coating materials that are wax-based, and similar materials where curing involves a liquid-to-solid phase change, the process may involve enabling heat from the article and liquid coating material to transfer to other medium, such as to gases in the surrounding environment (to facilitate convective heat transfer), and/or to solid materials that are in contact with the article (to facilitate conductive heat transfer). In another example, for coating materials for which curing involves an endothermic chemical reaction, and/or involves a heat induced internal structural change in the coating material, the process may involve baking the article and liquid coating material at an elevated temperature.
In this particular example, the nozzles 24 are arranged into a set of delivery nozzles 24d, and a set of extraction nozzles 24c, as shown in
The application system 10 includes a nozzle support chassis 36 on which the nozzles 24 are mounted. A reciprocation mechanism (not shown) is configured to move the nozzle support chassis 36, and thus also the nozzles 24. The reciprocation mechanism moves the nozzle support chassis 36—and thus also the nozzles 24—relative to the support bed 20 between a deployed position, and an elevated position. In use of the application system 10, when in the deployed position, the tip ends of the nozzles 24 are located within the cavities 7 of the blank 1. Further, the tip ends of the nozzles 24 are located below the datum plane PD, and the nozzles project through the datum plane PD. When the nozzles 24 are in the elevated position, the tip ends of the nozzles 24 are spaced above the support bed 20. Further, in the elevated position, the tip ends are spaced above the datum plane PD.
The application system 10 also has a support bed translation mechanism (not shown) that is configured to move the support bed 20 along a process path. The process path is indicated in
Further, when moving the support bed 20 along the process path PF the application system 10 controls the support bed translation mechanism to halt the movement of the support bed 20 to allow the nozzles 24 to reciprocate from the elevated position to the deployed position. To this end, the support bed translation mechanism is configured to index the support bed 20 along the process path PF through a set of predetermined positions. Each predetermined position corresponds with the concave nesting formations 22 being located such that the nozzles 24 are movable from the elevated positions to the deployed positions within cavities 7 of the blank 1.
The coating material transport subsystem includes a set of conduits (shown schematically in
In the example illustrated in
In this example, the coating material transport subsystem includes a bypass flow path 44 that interconnects the first and second flow paths 32, 34 in a manner that bypasses the nozzles 24. To this end, the bypass flow path 44 has a first end at which branches off the first flow path 32 between the outflow pump 38 and the separation of the first flow path 32 to the delivery nozzles 24d. A second end of the bypass flow path 44 merges with the second flow path 34 between the return-side pump 40 and the tank 12. An overpressure valve 46 is positioned in the bypass flow path 44.
When the blank 1 is loaded into the support bed 20, the underside of the blank 1 is preferably in direct contact with the upper surface of the support bed 20. This has several benefits in the operation of the application system 10, and in the formation of the coating 9 on the concave surfaces 3, as described in further detail below.
It will be appreciated that in
Once the blank 1 is loaded into the support bed 20, the support bed 20 is indexed along the process path PF for application of the coating of wax W.
The application system 10 then operates the reciprocation mechanism to move the nozzles 24 into their deployed positions, as shown in
In this particular example, the application system 10 has the set of delivery nozzles 24d that are arranged in a row that extends transversely to the process path PF. In addition, the set of extraction nozzles 24e are also arranged in a row that extends transversely to the process path PF. The rows of delivery and extraction nozzles 24d, 24e are spaced apart in the direction of the process path PF by the separation of adjacent rows of concave nesting formations 22 in the support bed 20, as will be apparent from
In operation of the application system 10 of this example, once the liquid wax W discharged into fill the cavities 7 in one row of the blank 1 reaches the desired level, the application system 10 then:
It will be appreciated that in the above phases of operation, the extraction nozzles 24e are being moved into cavities 7 that contain the liquid wax W. In some examples, the return-side pump 40 can be operated to continuously draw fluid (that is, gas, or liquid wax W) into the extraction nozzles 24e and then into the second flow path 34; at least while the extraction nozzles 24e are in positions away from the elevated position. In this way, as soon as the extraction nozzles 24e contact the liquid wax W within the cavities 7 (and prior to the extraction nozzles 24e reaching the deployed positions), the coating material transport subsystem commences extracting the first amount of liquid wax W from the cavities 7.
When the first amount of liquid wax W is extracted from each cavity 7, the residual amount of wax W will remain on the concave surface 3. The residual amount of wax W is then ready to cure, although it will be understood that in practice the curing process of the liquid wax W may have already commenced prior to all of the first amount of liquid wax W being extracted. The application system 10 is then ready to again operate the support bed translation subsystem to index the support bed 20 forward along the process path PF.
In this way, in use of the application system 10, the cavities 7 of the blank 1 are filled with liquid wax W that is discharged from the delivery nozzles 24d, and the first amount of liquid wax W is drawn back from within those cavities 7 via the extraction nozzles 24e for return to the tank 12.
From
The outflow pump 38 can be continuously operated to mitigate the wax W curing within the conduits of the first flow path 32. Accordingly, when the solenoid valves 42 close to halt the discharge of liquid wax W from the delivery nozzles 24d, the fluid pressure in the conduits of the first flow path 32 will rise. The overpressure valve 46 is set to open when the solenoid valves 42 are closed, so as to divert flow of liquid wax W to bypass the delivery nozzles 24d to merge with the second flow path 34, whereupon the wax W will be returned to the tank 12.
As will be appreciated, for application systems that are for use in application of coating materials that are in solid form at atmospheric conditions and in liquid form at elevated temperature, components of the application system will be heated to keep the coating material in liquid form. To this end, in the example of
The application system 10 can include a support bed temperature management subsystem that enables the temperature of the support bed 20 to be maintained at a predetermined temperature. In this example, resistive heating elements 48 are disposed in the support bed 20 to schematically illustrate part of the support bed temperature management subsystem. The heating elements 48 are controlled by the support bed temperature management subsystem to heat the support bed 20. Preferably, the predetermined temperature is to be below the liquid-solid phase transition temperature of the wax W. In this way, the rate of cooling of the wax W in the regions of the cavities 7 that are immediately adjacent the concave surfaces 3 is controllable, and thus the thickness of the coating 9 can be controlled. It will be understood that the components and performance of the support bed temperature management subsystem is dependent on many factors, including the properties (including the temperature) of liquid coating material that is discharged into the cavities 7, the support bed 20, and the environment within which the application system 10 operates. In some application systems, it may desirable or necessary for the support bed temperature management subsystem to alternatively or additionally have cooling circuits to cool the support bed 20.
It will be appreciated that the quantity of liquid wax W within the tank 12 will deplete in use of the application system 10. Accordingly, the quantity of liquid wax W in the tank 12 is replenished via the raw wax feed inlet 14.
The coating material transport subsystem includes flowmeters 52 in the first flow path 32. Each flowmeter 52 is in series with one of the delivery nozzles 24d, and measures the flow rate of wax W that is discharged from the opening of that respective nozzle 24d. More particularly, the flowmeter 54 measures the flow rate of liquid wax W flowing into the delivery nozzle 24d, and from that data the volume of discharged liquid wax W can be inferred.
In this example, the predetermined condition associated with filling the cavity 7 that is used by the application system 10 to close the solenoid valves 42 can be the volume of liquid wax W that is discharged into the respective cavity 7, as determined using data obtained from the flowmeter 52.
The coating material transport subsystem can optionally include flowmeters 54 in the second flow path 34. Each flowmeter 54 is in series with one of the extraction nozzles 24e, and measures the flow rate of wax W that is drawn into the respective extraction nozzle 24e from externally of that nozzle 24c. Data obtained by the flowmeters 54 can be used to assess whether or not the first amount of liquid wax W has been extracted from each cavity 7 via the extraction nozzle 24c.
As indicated above, following application of the coating 9 to the twenty concave surfaces 3 of the blank 1, the blank 1 is cut to form twenty vessels 5, one of which is shown in
The above described process to coat the concave surfaces 3 has the benefit that there is no need to mask the web 4 before applying the liquid wax W. Consequently, masking application and removal steps are obviated, with savings in material and processing time. Further, there is minimal waste in needless application of coating material. It will also be recognised that the above described process can minimize the generation of airborne droplets of liquid coating material. Consequently, the process can be used in applying liquid coating materials that are highly volatile, and/or present other dangers when airborne.
The nozzle 124 can be connected within an application system such that flow of liquid coating material through the two lumens 128, 129 can be selectively used at different phases of the coating application process. For example, when drawing liquid coating material out of a filled cavity, both lumens 128, 129 can be utilized for an initial period, which provides for high flowrate during the initial extraction. Subsequently, as the liquid coating material level approaches/reaches level of the annular opening 131, the annular lumen 129 can be closed off, thus allowing a slower flowrate that enables more complete extraction of the first amount of liquid coating material in the final extraction.
Alternatively or additionally, liquid coating material can be discharged via the annular lumen 129, and extracted via the central lumen.
As shown in
In addition, by virtue of the increased material volume of the side walls of the nozzle 224, the nozzle 224 can retain heat, which can mitigate liquid coating material curing on the outer surface 225 of the nozzle 224. In some examples, the application system can include heating elements to supply heat to the nozzles 224.
The principal difference between nozzle 324 compared with the nozzle 124 is the larger offset of the annular opening 331 from the central opening 330. When the nozzle 324 is in the deployed position and within the cavity 7 of a vessel 5 (as shown in
In use of the application system 310 to coat a concave surface of the vessel 5 with a coating material, the nozzle 324 is used both in discharging wax W into the cavity 7, and in extracting the first amount of wax W out from within the cavity 7, thereby leaving the residual amount of wax W coating the concave surface.
The application system 310 includes a valve 360. The first flow path 332 terminates at a first port of the valve 360, and the second flow path 334 starts from a second port of the valve 360. A third port of the valve 360 leads directly to the central lumen 328 of the nozzle 324.
The annular lumen 329 is connected via a vacuum line 366 to a vacuum pump 362. A trigger device, which in this embodiment is in the form of a venturi device 364, is positioned in the vacuum line 366. The venturi device 364 is interconnected with the stem of the valve 360, such that the operating state of the valve 360 is governed by the venturi device 364. Thus, the annular opening 331 is effectively a port to the venturi device 364.
The venturi device 364 has a first state when there is a first gas pressure in the vacuum line 366. This first state corresponds with the annular opening 331 being vented to atmosphere. The valve 360 has a first operating state when the venture device 364 is in its first state. In this first operating state, the valve 360 has the first and third ports open, and the second port is closed. Accordingly, wax W is able to flow from the tank 312 through the central lumen 328 of the nozzle 324 for discharge into the cavity 7.
The venturi device 364 has a second state when there is a second gas pressure in the vacuum line 366 that is lower than the first gas pressure. When the annular opening 331 is obstructed, for example by the annular opening 331 being covered by wax W, the gas pressure within the vacuum line 366 drops below atmosphere, and the venturi device 364 changes to its second state. The valve 360 has a second operating state when the venture device 364 is in its second state. In this second operating state, the valve 360 has the second and third ports open, and the first port is closed. Accordingly, wax W is drawn into the central lumen 328 from externally of the nozzle 324 and returned to the tank 12.
The valve 360 also forms a junction within the coating material transport subsystem. To this end, the valve 360 includes a fourth port that is permanently open to a bypass flow path 344. The bypass flow path 344 merges with the second flow path 334 between the return-side pump 340 and the tank 312. An overpressure valve 346 is positioned in the bypass flow path 344. In the event of an excess pressure within either the first or second flow paths 332, 334, the overpressure valve 346 opens to allow wax W to divert and return to the tank 312.
The vessel 405 includes a punt 470 that is positioned within a central portion of the base 402b with respect to the 405. Notwithstanding that the punt 470 creates a convexity with respect to the cavity 407 side of the base 402b, it will be apparent from
A nozzle 424 of an application system is used in extracting a first amount of the discharged wax W from the cavity 407.
The nozzle 424 has a central lumen 428 that opens at a central opening 430, and an annular lumen 429 that opens at an annular opening 431. The outer surface 425 of the nozzle 424 is shaped to substantially complement the shape of the concave surface 403. In this example, the central lumen 428 is positioned within the nozzle 424 such that the central opening 430 aligns with the centre of the punt 470 when the nozzle 424 is in the deployed position. Further, the annular lumen 429 is spaced radially from the central lumen 428 such that the annular opening 431 is aligned with the annular sump 472.
In this particular example, after the predetermined volume of wax W has been discharged into the cavity, the nozzle 424 is inserted into the discharged wax W. This action displaces liquid wax W upwardly within the cavity 407. In other words, liquid wax is displaced towards the rim 406 of the cavity 407, within the space between the side wall 402a and the nozzle 424, thus coating the side wall 402a to the rim 406.
Further, simultaneously with moving the nozzle 424 into the deployed position, liquid wax W is drawn from the cavity 407 through the central and annular lumens 428, 429 and into the second flow path of the coating material transport subsystem. In doing so, the first amount of liquid wax W is extracted from the cavity 407, leaving the residual amount to coat the concave surface 403.
The shape of the outer surface 425 of the nozzle 424 is such that the central opening 430 is rearward of the annular opening 431 with respect to the insertion direction of the nozzle 424. In other words, the portion of the outer surface 425 that is radially inward of the annular opening 431 has a slight concavity. To mitigate the possibility of air being trapped against the portion of the outer surface 425 that is radially inward of the annular opening 431, negative pressure may be applied to the central lumen 428 for a period before negative pressure is applied to the annular lumen 429. In this way, any trapped air can be extracted from the space between the nozzle 424 and the base 402b.
It will be appreciated that the exemplary application procedure that is described in connection with
The nozzle 424 itself may be constructed such that the outer surface 425 has a surface energy that is lower than the surface energy of the liquid wax W. This construction mitigates liquid wax W adhering to the outer surface 425 during application of the wax W. In some examples, the nozzle 424 may be formed from a material that has a low surface energy, may have a surface layer of a material that has a low surface energy, and/or the outer surface may be finished to minimize the surface energy.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021902187 | Jul 2021 | AU | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/AU2022/050749 | 7/15/2022 | WO |
