Spray gun for liquid compositions

Abstract

Spray gun (100) suitable for applying a liquid composition, such as a slurry mortar, to a surface.

Description

[0001] Spray gun for liquid compositions

[0002] Technical field of the invention

[0003] The present invention relates to a device for applying liquid compositions to a surface.

[0004] Background of the invention

[0005] The application of a plaster material to a surface, including walls, can be hard and time-consuming work, since it is often necessary to use tools, such as filling knives, to ensure a homogenous distribution and an even thickness of the material. Plaster compositions are difficult to apply and often require some form of post-processing before paint- or wall coverings, such as wallpaper or the like, can be applied.

[0006] W02020020996 discloses a spray gun suitable for applying uncured or unhardened plaster composition to a surface. The spray gun comprises an inlet for reception of a plaster material, an outlet for delivery of the plaster material, at least one compressed-air inlet, and a first and a second compressed-gas nozzle. The outlet is designed as an elongated slot, and the first and second compressed-gas nozzles are arranged above and below the elongated slot. The first and second compressed-gas nozzles aid in directing and lifting the plaster material away from the elongated slot. However, this configuration has certain limitations when it comes to properly distributing the material over surfaces and is only constructed to handle specific plaster compositions.

[0007] Summary of the invention

[0008] It is one object of the present invention to provide a solution that solves the above-mentioned problem.The inventor of the present invention has built a spray gun with a mixing chamber configured to receive and mix a liquid composition and gas (normally air, such as compressed air). The gas conduit comprises an elongate outlet extending along the width of the mixing chamber. This configuration improves the overall uniformity of the applied coating and reduces unwanted spray / splash from the spray gun. Furthermore, the gas directs and lifts the liquid composition away from the spray gun.

[0009] The liquid composition is preferably a dense liquid material, such as an uncured or unhardened plaster composition, a waterproofing membrane composition, or a slurry coating composition.

[0010] One aspect relates to a spray gun adapted for applying a liquid composition to a surface, the spray gun comprising:

[0011] - a hollow shaft having a first inlet configured to receive the liquid composition, wherein the liquid composition is preferably an uncured or unhardened plaster composition, or a slurry coating composition, preferably a slurry mortar;

[0012] - a housing in liquid communication with the hollow shaft, the housing having an elongate outlet extending along its width for delivering the liquid composition to the surface; and

[0013] - a gas conduit (preferably for delivering air, such as compressed air as interpreted within the field);

[0014] wherein the housing further comprises a mixing chamber configured to receive the liquid composition from the hollow shaft and gas from the gas conduit so as to mix the liquid composition with the gas; wherein the gas conduit comprises an elongate outlet extending along the width of the mixing chamber.

[0015] Another aspect relates to a system for applying an uncured or unhardened plaster composition to a surface, the system comprising:

[0016] - a hose with a first end, and a second opposite end, said hose adapted forreceiving and transporting an uncured or unhardened spray plaster composition; - a plastering machine operatively coupled to the first end of said hose, and adapted for pumping an uncured or unhardened spray plaster composition through said hose;

[0017] - a spray gun according to the present invention and operatively coupled to the second end of said hose.

[0018] Yet another aspect relates to a method for applying an uncured or unhardened plaster composition to a surface, the method comprising:

[0019] - providing a plastering machine adapted for pumping an uncured or unhardened spray plaster composition through a hose operatively coupled thereto at a first end;

[0020] - operatively coupling a spray gun according to the present invention to a second end of the hose; and

[0021] - applying an uncured or unhardened plaster composition to a surface by activating the spray gun.

[0022] Still another aspect relates to the use of a spray gun according to the present invention for applying an uncured or unhardened plaster composition to a surface.

[0023] Yet another aspect relates to a system for applying a slurry coating composition, preferably a slurry mortar, to a surface, the system comprising:

[0024] - a hose with a first end, and a second opposite end, said hose adapted for receiving and transporting a slurry coating composition, preferably a slurry mortar;

[0025] - a plastering machine operatively coupled to the first end of said hose, and adapted for pumping a slurry coating composition, preferably a slurry mortar, through said hose;

[0026] - a spray gun according to the present invention and operatively coupled to the second end of said hose.Another aspect relates to a method for applying a slurry coating composition, preferably a slurry mortar, to a surface, the method comprising:

[0027] - providing a machine adapted for pumping a slurry coating composition through a hose operatively coupled thereto at a first end;

[0028] - operatively coupling a spray gun according to the present invention to a second end of the hose; and

[0029] - applying a slurry coating composition to a surface by activating the spray gun.

[0030] Yet another aspect relates to the use of a spray gun according to the present invention for applying a slurry coating composition, preferably a slurry mortar, to a surface.

[0031] As used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and / or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about", it will be understood that the particular value forms another embodiment.

[0032] It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

[0033] Brief description of the figures

[0034] Figure 1 illustrates a perspective view of the spray gun according to the invention.Figure 2 illustrates perspective views of gas conduit heads according to the invention.

[0035] Figure 3 illustrates a schematic view of the spray gun according to the invention, where the shaft part is shown in two different positions relative to the housing.

[0036] Figure 4 illustrates a pivoting coupler for releasably coupling the shaft part and the housing according to the invention.

[0037] Figure 5 illustrates a perspective view of an alternative embodiment of the spray gun comprising a cylindrical gas antechamber.

[0038] Figure 6 shows a cross-sectional view of the spray gun of Figure 5, including the gas channel and divided rear portion of the mixing chamber.

[0039] Figure 7 illustrates a detailed view of the outlet region shown in Figure 6, including the ambient air channel and dimensional indications.

[0040] Detailed description of the invention

[0041] Overview of the spray gun and general concept

[0042] The inventor of the present invention has built a spray gun with a mixing chamber configured to receive and mix a liquid composition and gas. The gas conduit comprises an elongate outlet extending along the width of the mixing chamber. This embodiment is particularly useful in a construct where the housing has an elongate outlet extending along its width for delivering the liquid composition to the surface.

[0043] One aspect relates to a spray gun adapted for applying a liquid composition to asurface, the spray gun comprising:

[0044] - a hollow shaft having a first inlet configured to receive the liquid composition, wherein the liquid composition is preferably an uncured or unhardened plaster composition, or a slurry coating composition, preferably a slurry mortar;

[0045] - a housing in liquid communication with the hollow shaft, the housing having an elongate outlet extending along its width for delivering the liquid composition to the surface; and

[0046] - a gas conduit;

[0047] wherein the housing further comprises a mixing chamber configured to receive the liquid composition from the hollow shaft and gas from the gas conduit so as to mix the liquid composition with the gas; wherein the gas conduit comprises an elongate outlet extending along the width of the mixing chamber.

[0048] Liquid compositions and intended use

[0049] The spray gun can feed the liquid material in a direction away from the spray gun and at the same time provide an air lift for the liquid material, such as an uncured or unhardened plaster composition. The liquid composition may also be a waterproofing membrane composition, such as a wet-room waterproofing membrane composition.

[0050] The term “spray gun” refers to a tool suitable for spraying / delivering a particulate viscous liquid matter, such as an uncured or unhardened plaster composition. In the present context, the term “uncured or unhardened plaster composition” refers to a mixture consisting of plaster, water or other liquid acting as catalyst, curing agent, or solvent. The uncured or unhardened plaster composition preferably has a viscosity suitable for application with a spray gun according to the present invention. After application to a surface, e.g., after 15 minutes to 24 hours, the uncured or unhardened plaster composition will cure or harden and thereby become hard.

[0051] A surface may be a wall, e.g., a wall covered by insulation, such as stone wool,where it is desired to cover said stone wool with a plaster material. The plaster composition may thus be an alternative to mounting of molded plasterboards, which can be very hard work and often results in considerable waste material. The surface may also be a beam or a column that e.g., need fire protection.

[0052] Hollow shaft as liquid supply conduit

[0053] The hollow shaft may be a generally tubular member, e.g., cylindrical, having an interior passage defined by its walls. The shaft is configured to receive the liquid composition via a first inlet and to convey the liquid composition in a controlled manner from the inlet toward the mixing chamber. The internal diameter and wall thickness of the hollow shaft are selected to maintain the integrity of the fluid flow under operational pressures, thereby ensuring minimal pressure loss and optimized flow characteristics for subsequent mixing with gas. The hollow shaft may be fabricated from materials such as stainless steel, aluminum, or other corrosion-resistant and durable substances, depending on the specific application requirements.

[0054] Housing and mixing chamber

[0055] The mixing chamber is integrally formed within the housing and is configured to facilitate the controlled mixing of the liquid composition and gas. The chamber may be structured with distinct portions, such as a rear portion configured to receive the liquid composition from the hollow shaft and a front portion configured to receive the gas from the gas channel. The internal geometry of the mixing chamber may be designed, for example, with a funnel-shaped rear portion that gradually opens into a funnel-shaped front portion, which narrows toward the housing’s elongate outlet. This configuration promotes efficient mixing by generating turbulence and ensuring a homogeneous blend of the liquid composition and gas prior to ejection through the outlet. The internal surfaces of the mixing chamber are contoured to minimize flow separation and dead zones, thereby optimizing the atomization process and ensuring a consistent spray pattern. Material selection and dimensional parameters of the mixing chamberare chosen to withstand operational pressures and the abrasive nature of the materials being processed.

[0056] In one or more embodiments, the mixing chamber comprises a rear portion and a front portion, the rear portion being configured to receive the liquid composition from the hollow shaft, and the front portion being configured to receive the gas from the gas conduit, thereby facilitating the mixing of the liquid composition and the gas. The gas is introduced in the front portion to provide lift to the mixture.

[0057] In one or more embodiments, the rear portion of the mixing chamber is funnel-shaped and configured to open into the front portion, the rear portion being widest at the end facing the front portion.

[0058] In one or more embodiments, the front portion of the mixing chamber is funnel-shaped and narrows toward the housing’s elongate outlet.

[0059] The housing is preferably a rigid, preferably unitary, structural component configured to enclose and support the internal components of the spray gun, including the mixing chamber. The housing defines an internal cavity wherein the mixing chamber is formed, and provides fluid communication between the hollow shaft, the mixing chamber, and the housing’s outlet. The housing is designed with an elongate outlet extending along its width for delivering the mixed liquid composition to a target surface. In addition, the housing incorporates a gas conduit configured to deliver gas into the mixing chamber. The external surfaces of the housing are contoured to facilitate secure mounting, ease of handling, and to direct the spray pattern as required by the application. The housing is typically fabricated from materials offering sufficient strength, corrosion resistance, and durability under operational conditions, such as aluminum, stainless steel, or high-performance polymers. In one embodiment, the housing is configured to minimize internal turbulence outside the mixing chamber to ensure an optimal, homogeneous mixture of the liquid composition and gas before ejection.Gas conduit and gas outlet configurations

[0060] In one embodiment, the gas conduit is configured for being releasably coupled to the housing. The housing may include a slot configured to receive the tip of the gas conduit. The tip, which defines the outlet for the gas, may be adapted to be inserted through the slot into the mixing chamber, and more particularly into a front portion of the mixing chamber. The releasable coupling of the gas conduit to the housing may be achieved by any suitable detachable mechanism, such as a bayonet mount, snap-fit connection, threaded engagement, or the like, thereby facilitating maintenance, replacement, or reconfiguration of the gas conduit and tip assembly while ensuring proper positioning of the outlet within the mixing chamber to optimize the mixing process.

[0061] In one or more embodiments, the gas conduit’s outlet is relatively wider than the housing’s outlet. This embodiment optimizes the atomization process and ensures a consistent spray pattern.

[0062] Dimensions of housing outlet and gas outlet

[0063] In one or more embodiments, the housing’s outlet has a lateral span that is substantially greater than its vertical height.

[0064] In one or more embodiments, the width of the housing’s outlet is within the range of 3-12 cm, preferably within the range of 4-8 cm.

[0065] In one or more embodiments, the height of the housing’s outlet is within the range of 3-15 mm, preferably within the range of 5-10 mm.

[0066] In one or more embodiments, the gas conduit comprises an antechamber, preferably funnel-shaped, leading to, e.g., opening into, a plurality of channels, each with an outlet which opens into the tip of the gas conduit. The dimensions of the channels and outlets may be as discussed below.In one or more embodiments, the antechamber is funnel-shaped, and tapers to its broadest point at the transition to the plurality of channels. These channels extend from the antechamber and terminate in individual outlets at the tip of the gas conduit. The broadest section of the antechamber at the transition ensures optimal distribution of gas into the channels, maintaining consistent and controlled flow through each outlet. The broader transition point allows the antechamber to handle higher flow rates while ensuring consistent delivery across all channels. The gradual convergence of the gas flow and the broad transition may help minimize localized stress and turbulence, potentially increasing the lifespan of the nozzle.

[0067] In one or more embodiments, the gas conduit comprises a plurality of channels extending along the length of the housing, the channels being arranged side by side along the width of the housing, preferably wherein each of the said channels are of a length within the range of 5-100 mm, preferably within the range of IQ-50 mm.

[0068] In one or more embodiments, the plurality of channels each are of a length within the range of 5-100 mm, such as within the range of 10-90 mm, e.g., within the range of 15-80 mm, such as within the range of 20-70 mm, e.g., within the range of 25-60 mm, preferably within the range of 10-50 mm. The specific length of the channels makes the gas flow passing therethrough better directed than when the channels are e.g., 1 mm, i.e., when only an outlet is present, which causes more disturbance of the gas flow. The channel’s outlet may have a width or diameter within the range of 0.1-4 mm, such as 0.2-3 mm, e.g., 0.3-2 mm, such as 0.4-1.9 mm, e.g., 0.5-1.8 mm, such as 0.6-1.7 mm, e.g., 0.7-1.6 mm, such as 0.8-1.5 mm, e.g., 0.9-1.4 mm, such as 1.0-1.3 mm, e.g., 1.1 -1.2 mm. In one or more embodiments, the gas conduit comprises at least one channel per 5 mm length of the first outlet, such as 1-25 channels per 5 mm length of the first outlet, e.g., 2-20 channels per 5 mm length of the first outlet, such as 3-15 channels per 5 mm length of the first outlet, e.g., 4-10 channels per 5 mm length of the firstoutlet.

[0069] Preferably, each first and second gas nozzle comprises outlets with a width within the range of 0.1-4 mm, such as 0.2-3 mm, e.g., 0.3-2 mm, such as 0.4-1.9 mm, e.g., 0.5-1.8 mm, such as 0.6-1.7 mm, e.g., 0.7-1.6 mm, such as 0.8-1.5 mm, e.g., 0.9-1.4 mm, such as 1.0-1.3 mm, e.g., 1.1 -1.2 mm.

[0070] In one or more embodiments, the gas conduit is releasably fastened to the housing.

[0071] Pivoting coupler and adjustability

[0072] In one or more embodiments, the spray gun further comprises a pivoting coupler, either connected to the shaft part, or positioned between the shaft part and the housing, said pivoting coupler being in liquid communication with said shaft part and said housing, thereby being able to direct a liquid composition, e.g., uncured, or unhardened plaster, there between. Preferably, the pivoting coupler is releasably fastened to either the shaft part or to the housing, more preferably to both. In the present context, the term “pivoting coupler” is to be understood as a coupling between the shaft part and the housing that functions as a pivot joint, but at the same time also serves to direct liquid uncured or unhardened plaster composition from the shaft part to the housing.

[0073] In one or more embodiments, the pivoting coupler comprises:

[0074] - a base part coupled to said shaft part;

[0075] - a moving part coupled to said housing and rotatably mounted to said base part; and

[0076] - a locking mechanism adapted for releasably fastening said moving part at a given position relative to said base part.

[0077] In one or more embodiments, the spray gun further comprises a pivoting coupler positioned between said shaft part and said housing, or positioned between twoparts of the shaft part, said pivoting coupler being in liquid communication with said shaft part and said housing, thereby being able to direct a liquid composition there between.

[0078] In one or more embodiments, the pivoting coupler comprises:

[0079] - a base part coupled to said shaft part, or to a part of said shaft part;

[0080] - a moving part coupled to said housing, or to a part of said shaft part, and rotatably mounted to said base part; and

[0081] - a locking mechanism adapted for releasably fastening said moving part at a given position relative to said base part.

[0082] In one or more embodiments, the locking mechanism comprises:

[0083] - a plurality of cavities positioned at predetermined distances from one another; and

[0084] - a lock pin, roller, or ball adapted for partly fitting into each cavity, thereby making it at least more difficult for a user to rotate said moving part away from a given position relative to said base part;

[0085] wherein said cavities are formed in said base part, and wherein said lock pin, roller, or ball is mounted on said moving part, or vice versa. When the lock pin is used, the user will need to pull the pin out of the cavity in order to turn the moving part relative to the base part, while when the roller or ball is used, the roller or ball will roll out of the cavity if sufficient force is applied by the user. Preferably, the lock pin, roller, or ball is spring activated, e.g., such that the spring will act on the lock pin or ball to force them into a cavity.

[0086] In one or more embodiments, the gas conduit comprises flexible tubes, such as plastic tubes.

[0087] Extension shaft and flow adjustment

[0088] In one or more embodiments, the spray gun further comprises a hollow extension shaft, wherein said shaft part is adapted for engagement with said extensionshaft, and wherein said extension shaft is in liquid communication with said shaft part. As its name implies, the extension shaft serves to extend the shaft part. The length of the extension shaft may vary, but could preferably be from 10-500 cm. It could in some embodiments be telescopic.

[0089] In one or more embodiments, the gas conduit is configured with airflow adjustment means, such as a rotary valve, thereby being able to regulate the airflow through said gas conduit.

[0090] In one or more embodiments, the shaft part is configured with liquid composition flow adjustment means, such as rotary valves, thereby being able to regulate the flow of liquid composition through said first outlet.

[0091] In one or more embodiments, the extension shaft is configured with liquid composition flow adjustment means, such as rotary valves, thereby being able to regulate the flow of liquid composition through said first outlet.

[0092] The spray gun may comprise activating, regulating, and / or deactivating means, e.g., configured as electronics with turn knobs or push buttons, that are configured to control the machine that delivers the liquid (uncured or unhardened) plaster composition to the spray gun. Such means may regulate the rate of delivery of the liquid plaster composition to the spray gun by sending a signal (wired or wireless) to the machine about a wanted rate of delivery. Another signal may be a standby signal (e.g., be ready but do not deliver) or a signal to turn off the machine. Similar activating, regulating, and / or deactivating means may be present on the spray gun to activate, regulate, and / or deactivate the compressed air delivery to the first and / or second air channel.

[0093] The size of the spray gun is not as such limited but may be adjusted to its specific use. E.g., a handheld spray gun may be smaller than a spray gun held by a robotic arm or a chassis. The different parts of the spray gun may thereforebe sized accordingly.

[0094] In one or more embodiments, the housing’s outlet has a lateral span of at least 5 cm, such as at least 10 cm, e.g., at least 15 cm, such as at least 20 cm, e.g., at least 25 cm, such as at least 30 cm, e.g., at least 35 cm, such as at least 40 cm, e.g., at least 45 cm. The wider the outlet is, the larger the treatment area. The vertical height is also important to be able to provide an even flow of uncured or unhardened plaster composition. If it is too narrow, filler material may clot the outlet, and if it is too wide, the amount of uncured or unhardened plaster composition will be too large to be carried by the air stream from the gas conduit. Preferably, the housing’s outlet has a vertical height of at least 2 mm, such as within the range of 2-20 mm, e.g., at least 3 mm, such as within the range of 3-19 mm, e.g., at least 4 mm, such as within the range of 4-18 mm, e.g., at least 5 mm, such as within the range of 5-17 mm, e.g., at least 6 mm, such as within the range of 6-16 mm, e.g., at least 7 mm, such as within the range of 7-15 mm, e.g., at least 8 mm, such as within the range of 8-14 mm, e.g., at least 9 mm, such as within the range of 9-13 mm, e.g., at least 10 mm, such as within the range of IQ-12 mm, preferably within the range of 3-15 mm. The upper range may be dependent on the size of spray gun.

[0095] In one or more embodiments, the housing’s outlet has a lateral span of at least 5 cm, and a width within the range of 2-20 mm, preferably within the range of 3-15 mm.

[0096] It is preferred that the cross-sectional area of the housing’s outlet is identical to the cross-sectional area of the hollow shaft’s inlet in order to avoid accumulation of the liquid composition in the housing of the spray gun. The cross-section of the hollow shaft’s inlet can, e.g., be circle shaped, which will make it easy to attach to a hose.Typical operation and advantages

[0097] In general, a spray gun is provided, which is suitable for application of an uncured or unhardened plaster composition to a surface, e.g., a wall or a beam, where the uncured or unhardened plaster composition may be sprayed onto this surface homogeneously. The homogeneous distribution of the uncured or unhardened plaster composition is secured by the housing’s elongated outlet, which constitutes the outlet of the plaster material, and the gas conduit’s elongated outlet.

[0098] In a typical use situation, the user of the spray gun will make sure that the housing’s outlet is horizontal. The described use of a spray gun provides an easy and economical way of applying a plaster material, thereby resulting in great saving of working time compared to known methods. Due to the homogeneous distribution of the uncured or unhardened plaster composition on the surface, the subsequently hardened plaster composition is suitable for further processing, e.g., application of paint or wall coverings.

[0099] Systems and guided application

[0100] Another aspect relates to a system for applying a liquid composition, e.g., an uncured or unhardened plaster composition, to a surface, comprising:

[0101] - a spray gun according to the present invention; and

[0102] - a guide rail adapted for guiding the spray gun across a surface.

[0103] The guide rail is especially suitable for relatively large spray guns or at least for relatively large surfaces. The guide rail may be configured for releasably fastening to the ground and extending upwards relative to the ground.

[0104] Alternatively, or additionally, the guide rail may be releasably fastened to a ceiling.

[0105] In one or more embodiments, the spray gun is releasably fastened to a bracket being slidably connected to the guide rail.In one or more embodiments, the guide rail comprises two elongate rods, and wherein the spray gun is directly or indirectly (e.g., through a bracket) connected thereto. The elongate rods may in one end be configured for releasably fastening to the ground and extend upwards relative to the ground. Alternatively, or additionally, the elongate rods may at another end be configured for releasably fastening to a ceiling. The pressure from the applied uncured or unhardened plaster composition released from the first outlet may be enough to slide the spray gun up the elongate rods. Alternatively, the bracket may be motorized and configured for crawling or sliding up and down the two elongate rods. Obviously, the hose delivering the uncured or unhardened plaster composition to the spray gun needs to be of a length suitable for the spray gun being able to slide up and down the two elongate rods.

[0106] In one or more embodiments, the elongate rods are telescopic. Alternatively, the elongate rods may be configured for connection to extension rods.

[0107] Another aspect relates to a system for applying a liquid composition, e.g., an uncured or unhardened plaster composition, to a surface, comprising:

[0108] - a spray gun according to the present invention; and

[0109] - a robotic arm adapted for guiding the spray gun across a surface.

[0110] Yet another aspect relates to a system for applying a liquid composition, e.g., an uncured or unhardened plaster composition, to a surface, comprising:

[0111] - a spray gun according to the present invention; and

[0112] - an apparatus for delivering a liquid composition, e.g., an uncured or unhardened plaster composition, to said spray gun, said apparatus comprising an outlet shaped as a tube part, said tube part being in liquid communication with said spray gun, wherein apparatus further comprises a pump means operably connected to said outlet and adapted for pumping liquid uncured or unhardened plaster composition through said outlet.An apparatus for delivering liquid uncured or unhardened plaster composition to said spray gun may be of the type generally used within the art i.e., comprising a mixing chamber, a pump, and an outlet. Slight modifications may be necessary to allow for mixing the plaster composition with an adhesive, such as a pump, e.g., a dosage pump, adapted for pumping a dosage of adhesive into the mixing chamber of the apparatus, where water is normally also added / introduced to a plaster composition in powder form. The plaster composition in powder form may be mixed with an adhesive selected from the group consisting of: adhesives comprising an anionic copolymer dispersion of acrylic acid ester and styrene, polyvinyl acetate adhesives, polyvinyl alcohol adhesives, polyurethane adhesives, phenolic resin adhesives, cyanoacrylate adhesives, adhesives comprising an ethylene / vinyl acetate copolymer, adhesives comprising an ethylene-vinyl acetate-vinyl chloride emulsion, and mixtures thereof. The formed plaster composition may, e.g., comprise 6-15% by dry matter weight adhesive.

[0113] Another aspect relates to a system for applying an uncured or unhardened plaster composition to a surface, the system comprising:

[0114] - a hose with a first end, and a second opposite end, said hose adapted for receiving and transporting an uncured or unhardened spray plaster composition; - a plastering machine operatively coupled to the first end of said hose, and adapted for pumping an uncured or unhardened spray plaster composition through said hose;

[0115] - a spray gun according to the present invention and operatively coupled to the second end of said hose.

[0116] Yet another aspect relates to a method for applying an uncured or unhardened plaster composition to a surface, the method comprising:

[0117] - providing a plastering machine adapted for pumping an uncured or unhardened spray plaster composition through a hose operatively coupled thereto at a first end;- operatively coupling a spray gun according to the present invention to a second end of the hose; and

[0118] - applying an uncured or unhardened plaster composition to a surface by activating the spray gun.

[0119] Still another aspect relates to the use of a spray gun according to the present invention for applying an uncured or unhardened plaster composition to a surface.

[0120] Yet another aspect relates to a system for applying a slurry coating composition, preferably a slurry mortar, to a surface, the system comprising:

[0121] - a hose with a first end, and a second opposite end, said hose adapted for receiving and transporting a slurry coating composition, preferably a slurry mortar;

[0122] - a plastering machine operatively coupled to the first end of said hose, and adapted for pumping a slurry coating composition, preferably a slurry mortar, through said hose;

[0123] - a spray gun according to the present invention and operatively coupled to the second end of said hose.

[0124] Another aspect relates to a method for applying a slurry coating composition, preferably a slurry mortar, to a surface, the method comprising:

[0125] - providing a machine adapted for pumping a slurry coating composition through a hose operatively coupled thereto at a first end;

[0126] - operatively coupling a spray gun according to the present invention to a second end of the hose; and

[0127] - applying a slurry coating composition to a surface by activating the spray gun.

[0128] Yet another aspect relates to the use of a spray gun according to the present invention for applying a slurry coating composition, preferably a slurry mortar, to a surface.In the following, the invention will be described in detail by embodiments, which are not to be construed as limiting for the scope of the invention.

[0129] Figure 1 illustrates a spray gun 100 in perspective view. The spray gun comprises a hollow shaft 104 with a first inlet 102 for the reception of an uncured or unhardened plaster composition. The shaft 104 is connected to a hollow housing 101 with a first outlet 103 for delivery of the uncured or unhardened plaster composition, i.e., the shaft 104 and the housing 101 are in liquid communication.

[0130] The housing 101 defines an internal cavity wherein a mixing chamber 112 is formed. The internal cavity provides fluid communication between the hollow shaft 104, the mixing chamber 112, and the housing’s outlet 103. The mixing chamber 112 receives the liquid composition from the hollow shaft 104 and gas from a gas conduit 111, thereby allowing them to mix. The gas conduit 111 comprises an elongate outlet 114 (see Figure 2) extending along the width of the mixing chamber 112.

[0131] In the specific embodiment shown, the mixing chamber 112 comprises a rear portion 115 and a front portion 116, still defined by the walls of the housing 101. The rear portion 115 is configured to receive the liquid composition from the hollow shaft 104, and the front portion 116 is configured to receive the gas from the gas conduit 111. In this way, the gas is introduced into the liquid composition.

[0132] The rear portion 115 of the mixing chamber 112 is here shown funnel-shaped and configured to open into the front portion 116, which is also funnel-shaped and narrows toward the housing’s elongate outlet 103.

[0133] The gas conduit 111 is shown to be releasably fastened to the housing 101 , which allows for different types of gas conduit heads. In Figure 2, two types ofheads 111 A, 111 B are shown.

[0134] Both gas conduit heads comprise an antechamber 118 and a muzzle part 119. The antechamber 118 is funnel-shaped, opening into the muzzle part 119. The muzzle part 119 is configured to fit into a socket 120 (see Figure 1 ) formed in the housing 101. In the embodiment to the left (see Figure 2), i.e., 111 A, the elongate outlet 114 is configured as a single slot, whereas in the embodiment to the right, i.e., 111 B, the elongate outlet 114 is configured as a plurality of channels 117. These channels 117 extend along the length of the muzzle part 119, i.e., from the antechamber 118, and terminate in individual outlets at the tip of the gas conduit. The two types of outlets 114 can be used to adjust the gas flow into specific types of liquid compositions.

[0135] The housing 101 may in some embodiments be tiltably adjustable relative to a part 104B of the shaft part 104, or relative to an extension shaft (not shown). In Figure 3, it is illustrated how a part 104B of the shaft part 104 may be placed in two different positions relative to the housing 101 , shown by the aid of a pivoting coupler 105 positioned between two parts 104A, 104B of the shaft part 104 and the housing 101. The other shaft part 104A is directly coupled to the housing 101.

[0136] Figure 4 illustrates an exemplary pivoting coupler 105 for releasably coupling two shaft parts 104A, 104B (not shown). The pivoting coupler 105 is in liquid communication with the shaft parts 104A, 104B. This makes it capable of directing liquid uncured or unhardened plaster composition there between. The disclosed pivoting coupler 105 comprises a base part 106, and a moving part 107. The base part 106 is adapted for being coupled to one shaft part 104A, and the moving part 107 is adapted for being coupled to the other shaft part 104B. In principle, this could also be done the other way around, but the present configuration makes it easier to grasp the housing 101 to rotate it relative to the shaft part 104. Obviously, the moving part 107 is rotatably mounted to the basepart 106. The joint between the two may preferably be sealed against leakage of liquid uncured or unhardened plaster composition by a rotary sealing member (not shown). A locking mechanism 108,109 is present to releasably fasten the moving part 107 at a given position relative to the base part 106. The locking mechanism comprises a plurality of cavities 108 (here eight are visible) positioned along an arc-shaped line at predetermined distances from one another. Furthermore, the locking mechanism comprises a ball housing 109 comprising a ball (not shown) adapted for partly fitting into each cavity 108, thereby making it difficult for a user to rotate the moving part 107 away from a given position relative to the base part 106. This embodiment allows the user to operate the spray gun without worrying that the moving part 107, and hence the housing 101 , will dislocate from its position during use. At the same time, the locking mechanism allows the user to turn the moving part 107 relative to the base part 106 when needed with the use of appropriate force, thereby letting the ball enter into another one of the cavities 108. This operation may be eased if the ball is spring activated.

[0137] Alternative embodiment: cylindrical gas antechamber and slot outlet

[0138] In an alternative embodiment of the spray gun 100, illustrated in Figures 5 to 7, the gas conduit 111 comprises an antechamber 131 , preferably cylindrical in shape, arranged upstream of a narrow gas channel 132. The antechamber 131 is configured to feed gas, such as compressed air, into a slot-shaped outlet 133 that extends across the width of the housing 101 and opens into the front portion 116 of the mixing chamber 112. The slot-shaped outlet 133 preferably has a height of approximately 0.5 mm, allowing precise and directed airflow into the liquid composition. As shown in Figure 6, the gas flows from the antechamber 131 through the slot-shaped outlet 133 and into the gas channel 132, which extends along the width of the housing 101. This configuration enables a uniform sheet of gas to be introduced into the mixing chamber 112, enhancing spray uniformity and control.The shape of the antechamber 131 , particularly when cylindrical or otherwise rounded, has been observed to result in improved airflow performance. Without wishing to be bound by theory, it is believed that such a shape reduces turbulence and flow separation at the transition between the gas inlet and the slot-shaped outlet 133, promotes a more uniform pressure distribution across the slot outlet, and serves to dampen pressure fluctuations originating from the compressed gas source. In this way, the antechamber 131 may act as a form of plenum, allowing the gas to stabilize before entering the gas channel 132, and resulting in a more consistent and predictable flow into the mixing chamber 112. The enhanced control over the airflow improves the atomization of viscous liquid compositions, such as uncured plaster or slurry coatings, and may contribute to more stable and homogeneous spray patterns.

[0139] Furthermore, in this embodiment, the rear portion 115 of the mixing chamber 112 is subdivided into multiple parallel flow channels 134, preferably four, by internal wall sections 135. These channels 134 receive the liquid composition from the hollow shaft 104 and guide it toward the front portion 116 of the mixing chamber 112, which remains undivided to allow effective mixing and atomization with the gas delivered through the slot-shaped outlet 133. This structural configuration enhances the overall mixing efficiency and contributes to the consistent application of the liquid composition to a surface.

[0140] As illustrated in Figure 7, the outlet 103 of the housing 101 has a preferred vertical height of approximately 7.6 mm, although other dimensions may be used within the scope of the invention. Additionally, an air channel 136 is present between the gas channel 132 and the rear portion 115 of the mixing chamber 112, providing a pathway for ambient air to be drawn indirectly into the front portion 116 of the mixing chamber 112. Without wishing to be bound by theory, it is considered that the introduction of ambient air in this manner may influence the internal pressure or mixing dynamics within the chamber. For example, it may slightly dilute or expand the gas stream before it engages with the liquidcomposition, potentially contributing to a finer and more uniform spray, or moderating turbulence and pressure gradients near the outlet 103. However, the presence of this air channel 136 is not essential, and the spray gun 100 may function effectively in its absence.

[0141] Cylindrical antechamber as a plenum

[0142] In one or more embodiments, the gas conduit 111 comprises an antechamber 131 arranged upstream of a slot-shaped outlet 133 and upstream of the gas channel 132. The antechamber 131 may function as a pressure equalization chamber (plenum), thereby allowing gas from a compressed gas source to stabilize prior to discharge through the slot-shaped outlet 133. Without wishing to be bound by theory, it is considered that the antechamber 131 reduces localized velocity peaks and converts a more directional inlet flow into a more uniform static pressure field, thereby promoting a more uniform gas sheet entering the mixing chamber 112.

[0143] In one or more embodiments, the antechamber 131 provides damping of pressure pulsations originating from the compressed gas source, such that the gas flow delivered through the slot-shaped outlet 133 becomes more stable over time. This may improve atomization and reduce variations in the spray pattern when applying viscous liquid compositions, such as uncured plaster compositions or slurry coating compositions.

[0144] Cylindrical (or rounded) antechamber

[0145] In one or more embodiments, the antechamber 131 is cylindrical or otherwise rounded in cross-section. Without wishing to be bound by theory, it is considered that a cylindrical or rounded antechamber 131 promotes a more uniform radial pressure distribution compared to non-circular shapes, such as rectangular shapes, where corner regions may cause recirculation zones and non-uniform pressure distribution.In one or more embodiments, the cylindrical geometry further reduces flow separation at transitions between the gas inlet, the antechamber 131 , and the slot-shaped outlet 133, particularly when the transitions are configured with smooth changes in cross-sectional area. In this way, the cylindrical antechamber 131 may contribute to reduced turbulence upstream of the slot-shaped outlet 133, thereby improving uniformity of the gas sheet introduced into the mixing chamber 112.

[0146] Aspect ratio (L / D) guidance and preferred ranges

[0147] In one or more embodiments, the antechamber 131 has a length (L) and a diameter (D). The length-to-diameter aspect ratio (L / D) may be selected to promote pressure equalization prior to discharge through the slot-shaped outlet 133.

[0148] In preferred embodiments, the cylindrical antechamber 131 has an aspect ratio (L / D) within the range of 1.0-2.5, such as within 1.0-2.0, preferably within 1.2-1.6. Without wishing to be bound by theory, it is considered that an aspect ratio within these ranges improves dissipation of directional inlet effects and contributes to more uniform static pressure across the slot-shaped outlet 133, thereby improving uniformity of the gas sheet introduced into the mixing chamber 112.

[0149] In further embodiments, the cylindrical antechamber 131 may have an aspect ratio (L / D) below 1.0, e.g., within the range of 0.4-0.9, for example in compact designs where the axial length is constrained. Such “short and wide” plenums may still provide pressure equalization and pulsation damping when the cross-sectional area is sufficient and the inlet and outlet transitions are configured to reduce swirl or jetting effects.

[0150] Uniformity across long slot outlets with geometric ratios

[0151] In one or more embodiments, the slot-shaped outlet 133 extends along a substantial portion of the width of the housing 101 and / or the mixing chamber112. In such embodiments, uniform static pressure upstream of the slot-shaped outlet 133 may promote a substantially uniform gas sheet across the slot length.

[0152] In one or more embodiments, the antechamber 131 is dimensioned to provide a sufficiently large cross-sectional area and / or volume relative to the slot-shaped outlet 133, thereby promoting pressure equalization along the slot length.

[0153] Without wishing to be bound by theory, it is considered that such dimensioning reduces sensitivity to inlet non-uniformities and contributes to a more uniform interaction between gas and liquid composition within the mixing chamber 112, thereby improving coating uniformity and reducing unwanted spray / splash.

[0154] In one or more embodiments, the above may be expressed by one or more of the following geometric relations:

[0155] i) Plenum cross-sectional area to slot throat area ratio. In one or more embodiments, a ratio Ap / As is at least 10, such as within 10-500, preferably within 20-200, more preferably within 30-120, wherein Ap is the cross-sectional area of the antechamber 131 measured perpendicular to its longitudinal axis, and wherein As is a throat area of the slot-shaped outlet 133. The slot throat area As may be defined as As = h-w, where h is the slot height and w is the slot length, i.e. the lateral extent of the slot-shaped outlet 133 along the width of the housing 101.

[0156] ii) Antechamber diameter to slot height ratio. In one or more embodiments, a ratio D / h is at least 20, such as within 20-400, preferably within 40-200, more preferably within 60-150, wherein D is an internal diameter of the antechamber 131 , and h is the slot height of the slot-shaped outlet 133. Without wishing to be bound by theory, a relatively large D / h ratio may support conversion of directional inlet flow into a more uniform static pressure distribution upstream of the slotshaped outlet 133.iii) Plenum volume to slot throat area ratio. In one or more embodiments, a ratio Vp / As is at least 2 mm, such as within 2-200 mm, preferably within 5-80 mm, more preferably within 10-50 mm, wherein Vp is an internal volume of the antechamber 131 , and As is the slot throat area defined as As = h-w. Without wishing to be bound by theory, a relatively large Vp / As ratio increases compliance and damping upstream of the slot-shaped outlet 133, thereby promoting temporal stability and spatial uniformity of the gas sheet discharged through the slot-shaped outlet 133.

[0157] In one or more embodiments, the antechamber 131 is cylindrical, and the cross-sectional area Ap may be expressed as Ap = TTD2 / 4. In one or more embodiments, the above relations may be used individually or in combination to promote a substantially uniform gas sheet across the slot-shaped outlet 133, particularly where the slot-shaped outlet 133 extends along a substantial portion of the width of the housing 101.References

[0158] 100 Spray gun

[0159] 101 Housing

[0160] 102 Inlet

[0161] 103 Outlet

[0162] 104 Shaft

[0163] 105 Pivoting coupler 106 Base part

[0164] 107 Moving part

[0165] 108 Cavity

[0166] 109 Ball housing

[0167] 111 Gas conduit 112 Mixing chamber 114 Outlet

[0168] 115 Rear portion 116 Front portion 117 Channel

[0169] 118 Antechamber 119 Muzzle part

[0170] 120 Socket

[0171] 131 Antechamber 132 Gas channel 133 Outlet

[0172] 134 Flow channel 135 Wall section 136 Air channel

Claims

28Claims1. A spray gun (100) adapted for applying a liquid composition to a surface, the spray gun (100) comprising:- a hollow shaft (104) having a first inlet (102) configured to receive the liquid composition, wherein the liquid composition is preferably an uncured or unhardened plaster composition, or a slurry coating composition, preferably a slurry mortar;- a housing (101) in liquid communication with the hollow shaft (104), the housing having an elongate outlet (103) extending along its width for delivering the liquid composition to the surface; and- a gas conduit (111);characterized in that the housing further comprises a mixing chamber (112) configured to receive the liquid composition from the hollow shaft (104) and gas from the gas conduit (111 ) so as to mix the liquid composition with the gas; wherein the gas conduit (111) comprises an elongate outlet (114) extending along the width of the mixing chamber (112).

2. The spray gun (100) according to claim 1 , wherein the mixing chamber (112) comprises a rear portion (115) and a front portion (116), the rear portion (115) being configured to receive the liquid composition from the hollow shaft (104), and the front portion (116) being configured to receive the gas from the gas conduit (111), thereby facilitating the mixing of the liquid composition and the gas.

3. The spray gun (100) according to claim 2, wherein the rear portion (115) of the mixing chamber (112) is funnel-shaped and configured to open into the front portion (116), the rear portion (115) being widest at the end facing the front portion (116).

4. The spray gun (100) according to any one of the claims 2-3, wherein the frontportion (116) of the mixing chamber (112) is funnel-shaped and narrows toward the housing’s elongate outlet (103).

5. The spray gun (100) according to any one of the claims 1-4, wherein the gas conduit’s outlet (114) is relatively wider than the housing’s outlet (103).

6. The spray gun (100) according to any one of the claims 1-5, wherein the gas conduit (111) comprises a plurality of channels (117) extending along the length of the housing (101 ), the channels (117) being arranged side by side along the width of the housing (101 ), preferably wherein each of said channels (117) are of a length within the range of 5-100 mm, preferably within the range of 10-50 mm.

7. The spray gun (100) according to any one of the claims 1-6, wherein the housing’s outlet (103) has a lateral span that is substantially greater than its vertical height.

8. The spray gun (100) according to any one of the claims 1-7, wherein the width of the housing’s outlet (103) is within the range of 3-12 cm, preferably within the range of 4-8 cm.

9. The spray gun (100) according to any one of the claims 1-8, wherein the height of the housing’s outlet (103) is within the range of 3-15 mm, preferably within the range of 5-10 mm.

10. The spray gun (100) according to any one of the claims 1 -9, wherein the gas conduit (111) comprises an antechamber (131 ) configured to feed gas into a gas channel (132) extending along the width of the housing (101).

11. The spray gun (100) according to claim 10, wherein the antechamber (131 ) is cylindrical.

12. The spray gun (100) according to any one of the claims 10-11, wherein the gas channel (132) opens into the mixing chamber (112) through a slot-shaped outlet (133), preferably having a height of approximately 0.5 mm.

13. The spray gun (100) according to any one of the claims 11-12, the cylindrical antechamber (131 ) has a diameter within 30-60 mm.

14. The spray gun (100) according to any one of the claims 11-13, wherein the cylindrical antechamber (131) has a length-to-diameter aspect ratio within 1-5, thereby stabilizing gas pressure prior to the slot-shaped outlet (133).

15. The spray gun (100) according to any one of the claims 10-14, wherein the antechamber (131) is shaped to reduce turbulence and promote uniform pressure distribution across the gas slot (133).

16. The spray gun (100) according to any one of the claims 10-15, wherein the mixing chamber (112) comprises a rear portion (115) and a front portion (116), the rear portion (115) being configured to receive the liquid composition from the hollow shaft (104), and the front portion (116) being configured to receive the gas from the gas conduit (111), thereby facilitating the mixing of the liquid composition and the gas; wherein the rear portion (115) of the mixing chamber (112) is subdivided into a plurality of parallel flow channels (134) by internal wall sections (135), each configured to guide liquid composition toward the front portion (116) of the mixing chamber (112).

17. The spray gun (100) according to claim 16, wherein the front portion (116) of the mixing chamber (112) remains undivided to allow mixing of gas and liquid composition.

18. The spray gun (100) according to any one of the claims 2-17, wherein an air channel (136) is arranged between the gas channel (132) and the rear portion(115) of the mixing chamber (112), said air channel (136) being configured to allow ambient air to be drawn into the front portion (116) of the mixing chamber (112).

19. A system for applying an uncured or unhardened plaster composition to a surface, the system comprising:- a hose with a first end, and a second opposite end, said hose adapted for receiving and transporting an uncured or unhardened spray plaster composition; - a plastering machine operatively coupled to the first end of said hose, and adapted for pumping an uncured or unhardened spray plaster composition through said hose;- a spray gun (100) according to any one of the claims 1-18 operatively coupled to the second end of said hose.

20. A method for applying an uncured or unhardened plaster composition to a surface, the method comprising:- providing a plastering machine adapted for pumping an uncured or unhardened spray plaster composition through a hose operatively coupled thereto at a first end;- operatively coupling a spray gun (100) according to any one of the claims 1-18 to a second end of the hose; and- applying an uncured or unhardened plaster composition to a surface by activating the spray gun (100).

21. Use of a spray gun (100) according to any one of the claims 1 -18 for applying an uncured or unhardened plaster composition to a surface.

22. A system for applying a slurry coating composition, preferably a slurry mortar, to a surface, the system comprising:- a hose with a first end, and a second opposite end, said hose adapted for receiving and transporting a slurry coating composition, preferably a slurry32mortar;- a plastering machine operatively coupled to the first end of said hose, and adapted for pumping a slurry coating composition, preferably a slurry mortar, through said hose;- a spray gun (100) according to any one of the claims 1-18 operatively coupled to the second end of said hose.

23. A method for applying a slurry coating composition, preferably a slurry mortar, to a surface, the method comprising:- providing a machine adapted for pumping a slurry coating composition through a hose operatively coupled thereto at a first end;- operatively coupling a spray gun (100) according to any one of the claims 1-18 to a second end of the hose; and- applying a slurry coating composition to a surface by activating the spray gun (100).

24. Use of a spray gun (100) according to any one of the claims 1 -18 for applying a slurry coating composition, preferably a slurry mortar, to a surface.

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