Patent Application
20180050357
This application pertains to spray guns and the use thereof and, more particularly, to a method and apparatus for producing a gravity feed by means of a hollow needle and a single stage or two stage nozzle.
Liquid paints have become more and more important in recent years in various fields of applications including, vehicle coating and vehicle refinish coating. Vehicle refinish coating compositions are typically applied onto a substrate, i.e. an automobile vehicle body or body parts, using a manual spray gun and then cured to form the final coating layer
A known vehicle refinish spray gun includes an attached or remotely coupled pressure cup or pump system that delivers a liquid paint stream into the nozzle duct of the spray gun. Gravity feeding of the liquid paint was not possible because the spray gun utilized angular atomization which, when triggering, builds up an area of increased pressure (ΔP+) in front of the fluid tip and in the nozzle duct, as a result, will not permit a gravity feed. In addition, pressure feed or pump feed liquid paint dosing systems are very expensive and not user-friendly when using small amounts of liquid paints (e.g. 0.3 to 1 liters). Cleaning is also an issue, and expensive residual paint in the paint tubes from the feeding systems represent a major cost for the end user.
Therefore, it would be desirable to provide a user-friendly, gravity feed, liquid paint-cup-compatible spray paint system incorporating a single or two stage nozzle for use in the field of manual liquid paint applications. It would further be desirable that the spray paint system include a hollow needle coupled to an atomizing air duct for transporting a part of the atomizing air to a certain position in the nozzle duct that changes the area of increased pressure (ΔP+) back to an area of lower pressure (ΔP−).
This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.
In accordance with an embodiment, there is provided spray gun comprising a spray gun body, an air cap, a fluid spray nozzle having a fluid tip, a hollow needle, at least one air distribution channel for atomizing air, and at least one air distribution channel for fan air, wherein the fluid spray nozzle and the air cap are configured to direct an atomization air flow at an angle of 10 to 75 degrees relative to a pre-atomized coating composition jet, into the pre-atomized coating composition jet.
In accordance with a further embodiment, there is provided a fluid spray nozzle/air cap assembly for directing an atomization air flow at an angle of 15 to 60 degrees relative to a pre-atomized coating composition jet into a pre-atomized coating composition jet, comprising a duct, an atomizing air channel, and a hollow needle coupled via the duct to the atomizing air channel for transporting 50-150 li/min of the atomizing air into the spray nozzle, the fluid spray nozzle and the air cap providing an atomizing air pressure to fan air pressure ratio of substantially 0.5 to 1.0.
In accordance with a still further embodiment, there is provided a method for applying a layer of a water-based coating composition onto a substrate with a spray gun. The method comprises directing an atomization air flow at an angle of substantially 15 to 60 degrees through an atomizing air channel, relative to a pre-atomized coating composition jet, into the pre-atomized coating composition jet, transporting, with a hollow needle that is coupled via a duct to the atomizing air channel, substantially 50-150 li/min of the atomizing air into a fluid spray nozzle; providing an atomizing air pressure to fan air pressure ratio of substantially 0.5 to 1.0 via the fluid spray nozzle and the air cap, and applying at least one layer of the water-based coating composition onto a substrate, wherein the water-based coating composition is applied with an atomizing air pressure to fan air pressure ratio of substantially 0.1 to 10.
The embodiments described herein are directed to a spray gun, specifically a manual spray gun, particularly suited for applying a layer of a water-based coating composition onto a substrate, the spray gun comprising a spray gun body, an air cap, a fluid spray nozzle duct having a fluid tip that includes a hollow needle, at least one air distribution channel for the atomizing air, and at least one air distribution channel for the fan air, and a hollow needle that is connected to an atomization air duct, transporting a certain atomization air volume to the nozzle duct at a well-defined position in the nozzle duct when fully triggering the spray gun.
This atomization air volume, substantially 50 to 150 li/min, preferably substantially 80-120 li/min. will create a pressure drop in the nozzle duct and in front of the nozzle tip, assuring a vacuum in the gravity cup. The vacuum is measured in a range of substantially 20-500 PA (Pascale) depending on the diameter of the hollow needle/nozzle tip, the air volumes through the needle, and the atomizing air pressure at fluid tip originated by the angular atomization.
Spray guns in accordance with the prior art vacuum measured substantially 40-400 PA using specified atomizing air (AA) pressure between substantially 2-3 bar pressure at the heel of the gun. Guns tested included the Sata RP4000 jet, Iwata WS400, Devilbiss GTI Pro, Devilbiss GTI PRO lite, and the Sata 3000 HVLP
Furthermore, other desirable features and characteristics of the system and method will become apparent from the following detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.
Embodiments of the subject matter will hereinafter be described in conjunction with the following figures, wherein like numerals denote like elements, and:
The features and advantages of the present invention will be more readily understood, by those of ordinary skill in the art, from reading the following detailed description. It is to be appreciated that certain features of the invention, which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. In addition, references in the singular may also include the plural (for example, “a” and “an” may refer to one, or one or more) unless the context specifically states otherwise.
Water-based coating compositions are coating compositions, wherein water is used as a solvent or thinner when preparing and/or applying the coating composition. Usually, aqueous coating compositions contain about 20% to 80% by weight of water, based on the total amount of the coating composition and optionally, up to about 15% by weight, preferably, below about 10% by weight of organic solvents, based on the total amount of the coating composition.
The spray gun of the embodiment described herein or which can be suitable in the methods described herein is particularly suited as a manual (or hand-held) spray gun. A manual spray gun is a spray gun which is used manually by a human, i.e. a coating composition is manually sprayed with the spray gun by a human. A manual spray gun is not a spraying device used in or as a spraying robot or a spraying machine or robot or handled by a spraying machine or spraying robot. Manual spray guns are typically used for applying coating compositions in vehicle refinishing, particularly in vehicle repair coating in refinish body shops. However, the spray gun of the present invention can also be used in a spraying robot or a spraying machine or can be handled by a spraying robot or a spraying machine.
Atomizing air (AA) is defined as the airflow or air volume that breaks the liquid paint jet, which will be used hereinafter synonymously with coating composition jet, coming from the fluid tip of the fluid spray nozzle, into small droplets. Fan air (FA) is defined as the airflow or air volume that pushes the atomized paint jet into a desired paint jet form, such as a spherical form, and preferably an elliptical cone.
The spray gun in accordance with an embodiment and which can be used in the method of the embodiment is operable by using high air volume and high air pressure, measured at the air cap outlet.
Air volumes of, for example, substantially 50 liters/minute (l/min) to 600 l/min, preferably substantially 100l/min to 600l/min, and more preferably substantially 200l/min to 500 l/min, measured at the air cap outlet, can be used. Atomizing air volume and fan air volume can be separately in the range of substantially 50l/min to 600l/min, and preferably substantially 100l/min to 500l/min. A respective input air volume is selected accordingly.
The atomizing air pressure can, for example, be in the range of substantially 0.5 bar to 5.0 bar, preferably substantially 1.0 bar to 5.0 bar, still more preferably substantially 2.0 to 4.0 bar, measured at the air cap outlet. The fan air pressure can be, for example, in the range of substantially 0.5 bar to 5.0 bar, preferably substantially 1.0 bar to 5.0 bar, and still more preferably substantially 2.0 bar to 4.0 bar, measured at the air cap outlet. Accordingly, an input air pressure of, for example, substantially 2.0 to 12.0 bar is needed. The respective input air pressure can be generates by a turbine compressor.
The spray stream or coating composition jet may be produced by using a gravity cup. Even if compressed air is preferably used and referred to herein throughout, other pressurized carriers, such as compressed gas other than air or a compressed gas mixture, can also be used.
The spray gun and the method of the embodiments described herein has a fluid spray nozzle and an air cap which are both configured to direct an atomization air flow at an angle of substantially 10-75 degrees, preferably substantially 15-60 degrees, and more preferably substantially 30-45 degrees (relative to the coating composition jet) into the coating composition jet. Stated differently, the fluid spray nozzle and the air cap are both configured such that the angle formed by the central axis of the coating composition jet and the central axis of the atomization air flow is substantially 10-75 degrees, preferably substantially 15-60 degrees, and still more preferably substantially 30-45 degrees. The central axis of the coating composition jet is at a ninety degree angle relative to the fluid tip surface or laminar to the fluid tip opening.
Accordingly, the fluid spray nozzle is configured such that it has the form of a substantially 10-75 degree, preferably substantially a 15-60 degree, and still more preferably substantially a 30-45 degree cone terminating to a substantially 10-75 degree, preferably substantially 15-60 degree, and still more preferably a substantially 30-45 degree angular fluid tip. Accordingly the air cap is formed with a central substantially 10-75 degree, preferably substantially 15-60 degree, and still more preferably substantially 30-45 degree angular air aperture (opening). The profile of the fluid spray nozzle is a substantially 10-75 degree, preferably substantially 15-60 degree, and still more preferably 30-45 degree frustum, terminating at the substantially 10-75 degree, preferably substantially 15-60 degree, and more preferably substantially 30-45 degree angular fluid tip, through which the water-based coating composition is discharged (see
During operation of the spray gun a first flow of atomizing air is transported through the hollow needle and causes a pre-atomization of the coating composition jet in the nozzle. A second flow of atomization air emerges through the gap between the fluid spray nozzle and the air cap. This atomizing airflow hits the pre-atomized paint jet, i.e., the coating composition jet, coming out of the fluid tip of the nozzle (which has a conical form—see
The other substantially 50-90%, more preferred substantially 65-75% of the total atomization air volume is directed at an angle of substantially 10-70 degrees, preferably substantially 15-60 degrees, and more preferably substantially of 30-45 degrees (relative to the coating composition jet) into the pre-atomized paint jet. The fluid spray nozzle and air cap can contain additional bores to direct the remaining part of the atomization air volume.
Generally the fluid spray nozzle and the air cap of a spray gun form a unified system, i.e. a specific fluid spray nozzle requires a specific air cap configured to match; for example, the opening of the air cap has to be adjusted according to the diameter of the fluid tip of the nozzle.
The fluid spray nozzle and the air cap of the spray gun, together with the air distribution channels, are configured to provide an atomizing air pressure to fan air pressure ratio (AA/FA ratio) of substantially 0.1 to 10, preferably substantially 0.5 to 1.0, and more preferably substantially of 0.6 to 0.9, measured at the air cap outlet. The AA/FA ratio can be, for example, 2 bar:3 bar to 2.5 bar:3 bar. The design of the fluid spray nozzle and the air cap can be configured in different ways in order to ensure the desired AA/FA ratio. The fluid spray nozzle and the air cap contain at least one air channel for the atomizing air and at least one air channel for the fan air. According to one embodiment the diameter of the air channels can be selected such that the desired AA/FA ratio can be adjusted in the operation status of the spray gun. According to a further embodiment means can be included for regulating the air flow volumes (and accordingly the air pressure) in the separate air channels at given air channel diameters. Air flow volumes can be regulated, for example, by air valves. Also, according to yet a further embodiment, both of the above measures, the air channel diameter and the regulation of the air flow volume by respective means, can be used. The selection of appropriate air channel diameters and air flow volume regulating means can be made by a person skilled in the art.
In addition, the fluid spray nozzle or the air cap or both may contain bores to direct the atomization or the fan air flow. The number, diameter, and position of the respective bores may be selected by a person skilled in the art so as to achieve the desired air volume and air pressure.
The manual spray gun in accordance with the present embodiment comprises the spray gun body, an air cap at the front of the spray gun body, a fluid spray nozzle and a hollow needle. The air cap is formed with horns in order to supply the fan air. The spray gun comprises at least two air distribution channels, one for the atomizing air and another for the fan air. According to one embodiment, the compressed air enters the spray gun body via an inlet air channel, e.g. a central inlet air channel. The inlet air channel is separated into the at least one atomizing air channel and at least one fan air channel.
According to a further embodiment, the incoming compressed air may directly be divided at the air inlet into at least one atomization air stream and at least one fan air stream. The air distribution channels are configured accordingly. Preferably, the spray gun comprises a compressed air distribution system; i.e. it comprises at least one compressed air inlet channel and two separate air distribution channels—one for the atomization air and one for the fan air. The spray gun body preferably comprises means dividing the incoming air into a first air flow that provides atomizing air around the fluid spray nozzle and in the hollow needle and into a second air flow that provides the fan air to the horns of the air cap. One or more air channels for the atomizing and the fan air may be present.
Separation and regulation of the compressed input air into atomizing air and fan air can be realized by means of air valves independently regulating the atomizing and fan air volume (and accordingly the air pressure).
According to a further embodiment, the spray gun can additionally have pressure valves and digital read-out on the separate air channels, regulating separately the atomizing air flow and fan air flow to set the desired ratio AA/FA, measured at the air cap outlet. The fluid spray nozzle may have a fluid tip opening diameter of substantially 0.1 to 5 mm or substantially 0.7 to 2.5 mm.
The spray gun body may have additional multiple parts and controls, as typically used in manual spray guns; for example, a flow regulator for regulating the flow of the coating composition, and other mechanisms necessary for proper operation of a manual spray gun known to those skilled in the art. Typically, multiple channels, connectors, connection paths, and mechanical controls can be assembled within the spray gun body.
The previously described design of the fluid spray nozzle, the air cap, and hollow needle, in combination with at least one atomizing air channel and the at least one fan air channel, permit adjustment of the desired AA/FA pressure ratio and direct the atomization air flow at the desired angle into the pre-atomized coating composition jet.
The present embodiments descried herein also relates to a fluid spray nozzle/air cap/hollow needle assembly, wherein A) the fluid spray nozzle and the air cap are configured to direct an atomization air flow at an angle of substantially 10 to 75 degrees, preferably substantially 15 to 60 degrees, and more preferably substantially 30 to 45 degrees, relative to the pre-atomized coating composition jet, into the pre atomized coating composition jet, and B) the fluid spray nozzle/the air cap/the hollow needle are configured to provide an atomizing air pressure to fan air pressure ratio of substantially 0.1 to 10, and preferably substantially 0.5 to 1.0.
The details, embodiments, and preferred embodiments of the fluid spray nozzle, the air cap, and the hollow needle of the fluid spray nozzle/air cap/hollow needle assembly are the same as described above for the fluid spray nozzle, the air cap, and hollow needle as part of the spray gun. The fluid spray nozzle/air cap assembly can be used in any type of spray gun, for example in a manual spray gun, and also in a spraying robot, a spraying machine, or any other spraying device.
In an embodiment, a layer of a water-based coating composition is applied onto the substrate by the above described spray gun, with an atomizing air pressure to fan air pressure ratio of substantially 0.1 to 10, preferably substantially 0.5 to 1.0, and more preferably substantially 0.6 to 0.9.
The spray gun and the fluid spray nozzle/air cap/hollow needle assembly and the method of use thereof can specifically be used for applying water-based coating compositions. Typical water-based coating compositions comprise binders, optionally cross-linkers, and a liquid carrier. The liquid carrier is water and may comprise in addition one or more organic solvents. Binders are, for example, compounds with functional groups with active hydrogen. These compounds can be oligomeric or polymeric binders. In order to ensure sufficient water dilutability of the binders, they are modified to render them hydrophilic, e.g., they can be anionically modified by incorporation of acid groups. The water-based coating compositions may contain cross-linkers, for example, polyisocyanates with free isocyanate groups. Examples of polyisocyanates are any number of organic di- or higher functional isocyanates with aliphatically, cycloaliphatically, araliphatically and/or aromatically bound free isocyanate groups. The polyisocyanate cross-linkers are those commonly used and commercially available in the paint industry and are described in detail in the literature.
The water-based coating compositions may contain pigments, solid pigments as well as effect pigments, fillers, and/or usual coating additives. Examples of usual coating additives are light stabilizers, for example, based on benztriazoles and HALS (hindered amine light stabilizer) compounds, flow control agents based on (meth)acrylic homopolymers or silicon oils, rheology-influencing agents, such as, highly disperse silicic acid or polymeric urea compounds, thickeners, such as, cross-linked polycarboxylic acid or polyurethanes, anti-foaming agents, and wetting agents.
The water-based coating compositions to be applied with the spray gun and the fluid spray nozzle/air cap assembly can be any kind of paints such as waterborne clear coats, water-borne top coats, water-borne base coats, and water-borne primers.
The water-based coating composition may be applied onto a pre-coated substrate. Suitable substrates are metal and plastics substrates, in particular, the substrates known in the automotive industry, such as for example iron, zinc, aluminium, magnesium, stainless steel or the alloys thereof, together with polyurethanes, polycarbonates or polyolefines. In the case of a multilayer coating with a water-based base coat composition and water-based clear coat composition, the clear coat layer may be applied onto the base coat layer either after drying or curing or wet-on-wet, optionally after briefly flashing off. They water-based coating compositions may comprise a one-component or two-component coating. After the layer of the water-based coating composition has been applied, it may initially be flashed off to remove water and optionally present organic solvent. Curing may then proceed at ambient temperature or thermal curing may proceed at temperatures of, for example, substantially 40 to 140° C., and preferably at substantially 40 to 60° C.
The spray gun and the fluid spray nozzle/air cap assembly for applying water-based coating compositions and the method can preferably be used in vehicle repair coating, but also in an original vehicle production line painting as well as for coating large vehicles and transportation vehicles, such as trucks, busses, and railroad cars. However, the spray gun can also be used for applying water-based coating compositions onto other substrates in other fields of application; for example, onto wood, plastic, leather, paper and other metal substrates as well as onto woven and nonwoven fabrics.
In accordance with an embodiment, the spray gun comprises a spray gun body 12, (e.g.
The atomizing air pressure and air volume stream as well as the fan air pressure and air volume stream can be regulated by the nozzle and air cap design. The atomizing air pressure and the fan air pressure can be regulated by configuring relative sizes of the atomization air distribution channel 30 and the fan air distribution channel 26 (e.g.,
The fluid spray nozzle and the air cap can be assembled to form the fluid spray nozzle and air cap assembly via conventional mechanisms, such as matching screw tracks, clippers, or other mechanisms to assemble the parts. The fluid spray nozzle may comprise a spray needle 22 that slides along the rotational axis Z-Z′ of the fluid spray nozzle in the directions shown by the arrow 32 between a closed position and an open position to close or open the fluid tip orifice 20 inside the fluid spray nozzle (
The air cap opening inner-surface 62 is a surface inside the air cap towards the fluid spray nozzle immediately around the air cap opening 66 and can be the entire (
The atomization air flow is directed through an atomizing air passage 83 a space formed by the air cap opening inner-surface 62 of the air cap (
The fluid spray nozzle 18 can have a total external nozzle surface angle 76 (e.g.
The air cap 14 can further comprise two or more fan air horns 28 (e.g.,
The fluid spray nozzle and air cap assembly is free from any structure disrupting or changing the atomization air flow 24 at the atomization air flow angle 84 (e.g.,
The air cap can have an air cap rim 70 immediately around the air cap opening 66 (
The atomization air flow angle 84 can be measured between the projected atomization air flow 24 and the rotational axis Z-Z′ of the fluid spray nozzle on a perspective cross-section plane 88 intersecting the rotational axis Z-Z′ and parallel to the rotational axis Z-Z′ (
Coating compositions suitable for using the spray gun in accordance with the embodiments described herein can be any coating compositions that are suitable for spraying with a spray gun. The coating composition can be a solvent borne coating composition that comprises from substantially 10% to 90% of one or more organic solvents, or a waterborne coating composition that comprises from substantially 20% to 80% of water based on the total weight of the coating composition.
The coating composition can be a “two-pack coating composition”, also known as a 2K coating composition, with two components of the coating composition stored in separate containers and sealed to increase the shelf life of the components of the coating composition during storage. The coating composition can be a “one-pack coating composition”, also known as a 1K coating composition, such as a radiation curable coating composition or a coating composition contains cross linkable components and blocked crosslinking components such as blocked isocyanates that can be deblocked under certain deblocking conditions.
The coating composition can be a mono-cure or a dual cure coating composition. A mono-cure coating composition can be cured by one curing mechanism. In one example, a mono-cure coating composition can contain one or more components having acrylic double bonds that can be cured by UV radiation in which the double bonds of the acrylic groups undergo polymerization to form a cross-linked network. In another example, a mono-cure coating composition can be cured by chemical crosslink and contain crosslinking groups and cross linkable groups that can react to form a cross-linked network. A dual-cure coating composition is a coating composition that can be cured by two curing mechanisms, such as UV radiation and chemical crosslink.
Examples of a hollow needle can include those shown in
Hollow needle devices may be provided with an extension such as is shown at 91 in
A single stage nozzle is one in which the inner nozzle surface 93 is configured to have an internal surface at one angle; i.e. oriented at a single angle (e.g. 78 in
While at least one exemplary embodiment has been presented in the foregoing detailed description, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the present disclosure in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the present disclosure as set forth in the appended claims and their legal equivalents.
This application is a U.S. National-stage entry under 35 U.S.C. §371 based on International Application No. PCT/US2015/019931, filed on Mar. 11, 2015 which was published under PCT Article 21(2) and is incorporated in its entirety herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2015/019931 | 3/11/2015 | WO | 00 |
