Nozzle body for liquid spray gun

Abstract

A nozzle body (1) for a liquid spray gun, the nozzle body comprising a tubular nozzle tube (66) comprising: a) a nozzle tube channel (58) extending between a nozzle tube inlet and a nozzle tube outlet (52) through which liquid exits the nozzle tube channel (58); and b) a nozzle tube wall (71) having a radially outer surface (75). The outer surface (75) of the nozzle tube wall (71) is operable to engage with the surface of the gas cap to form an atomized gas outlet disposed circumferentially around the nozzle tube outlet (52) such that pressurized atomized gas (110) exits through the atomized gas outlet and into the outside air (93) and atomizes the liquid. A radially outer surface (75) of the nozzle tube wall (71) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet angularly away from the spray axis (200). A radially inner surface (76) of the nozzle tube wall (71) is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet (52) angularly away from the spray axis (200).

Description

[0001] The present disclosure relates to liquid spray guns in which a liquid to be sprayed is atomized by a pressurized gas. The present disclosure more particularly relates to a nozzle body for use in such spray guns, a nozzle assembly comprising such a nozzle body, and a machine-readable medium having stored thereon data representing a model of such a nozzle body or nozzle assembly.

[0002] Spray guns according to the present disclosure are used, for example, in many automotive repair shops to apply liquid paint to the surfaces of vehicles using pressurized air or another pressurized gas. Most of these spray guns have a spray gun body or gun platform with a trigger and a handle for manual spray operation, while other spray guns are used with robots and are equipped with mechanical or electrical interfaces to allow computer-controlled spray operation by the robot.

[0003] Spray technology and environmental regulations are trending toward the use of lower gas pressures or spray guns that can be laboratory certified to produce a specific level of paint “transfer efficiency”. The challenge with using lower gas pressures is that the amount of energy available to draw out and atomize liquid paint is reduced. This situation can have a negative impact on application speed and paint finish quality. This challenge is further exacerbated as paint manufacturers are moving toward liquid paint formulations that are waterborne and have increased solids content. These liquid paints tend to have higher viscosities that can result in reduced paint flow and more difficult atomization of the liquid paint at the same gas pressure and gas flow. Stronger atomizing gas flow can provide finer atomization that generates a finer paint spray. However, increasing the pressure of the atomizing gas increases the volume of undesirable high frequency noise, typically results in lower transfer efficiency, increases the consumption of pressurized atomizing gas, and results in higher operating costs.

[0004] U.S. patent application published as US 2020 / 0030831 Al attempts to address these issues and proposes a spray gun having a fluid nozzle head comprising a gas cap and a paint nozzle, wherein the gas cap comprises an inner surface and the paint nozzle comprises an outer surface, the inner surface and the outer surface defining two sides of an air passage and being defined by profiles, each profile terminating to form an air passage outlet for discharging an air jet proximal to a paint nozzle outlet of the paint nozzle. The profiles are configured to provide a velocity profile of the air flow through the air passage outlet in which the velocity of the air radially closer to the paint nozzle outlet is significantly higher than the velocity radially further away from the paint nozzle outlet.

[0005] To conserve energy and paint during paint spray application, new spray gun designs are needed that can effectively utilize the driving force of the compressed atomizing gas to draw out and atomize liquid paint using lower gas pressures or that consume less pressurized gas.

[0006] To address these needs, the present disclosure provides a nozzle body for a liquid spray gun for spraying a liquid, the nozzle body comprising a tubular nozzle tube comprising

[0007] a) an elongated nozzle tube passage extending longitudinally between a nozzle tube inlet, through which the liquid enters the nozzle tube in use, and a nozzle tube outlet, through which the liquid exits the nozzle tube passage in use in a spray direction, wherein a length direction of the nozzle tube passage defines an axial direction and a radial direction orthogonal to the axial direction,

[0008] b) a nozzle tube wall having a radially outer surface and an opposite radially inner surface, the radially inner surface bounding the nozzle tube passage and being in contact with the liquid in use,

[0009] wherein the spray direction of a centroid of a cross section through the nozzle tube outlet defines a spray axis, wherein the nozzle tube outlet is arranged around and comprises the spray axis, wherein the outer surface of the nozzle tube wall is operable to form, in conjunction with a surface of a gas cap when the gas cap is directly or indirectly connected to the nozzle body, an atomizing gas outlet arranged circumferentially around the nozzle tube outlet such that pressurized atomizing gas exits through the atomizing gas outlet and into the external air and atomizes the liquid after the liquid has exited the nozzle tube outlet, characterized in that the outer surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis, and the radially inner surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis.

[0010] In a nozzle body according to the present disclosure, the outer surface of the nozzle tube wall directs atomizing gas emanating from the annular atomizing gas outlet angularly away from the spray axis. Within this angularly outwardly directed flow of atomizing gas, the pressure at the nozzle tube outlet is lower than in a conventional geometry in which atomizing gas flows in a direction along or towards the spray axis. The lower pressure at the nozzle tube results in more liquid being drawn from the nozzle passage and increased liquid (e.g. paint) flow, but the consumption of pressurized gas is not changed relative to a conventional nozzle body. To obtain a similar liquid flow as obtained with a conventional nozzle body, the pressure and / or volume of pressurized atomizing gas can be reduced in a spray gun featuring a nozzle body according to the present disclosure. This can result in energy and cost savings. The lower pressure of atomizing gas can also result in less or lower amounts of high frequency noise being produced during a spray operation, which reduces occupational noise exposure and associated health risks for human operators.

[0011] The beneficial effect of the lower pressure at the nozzle tube outlet is further enhanced by the fact that portions of the liquid are also directed radially outward. By the synergy between the atomizing air directed outward by the outer nozzle tube surface and the portions of the liquid directed outward by the inner nozzle tube surface, the pressure drop zone in front of the nozzle tube outlet is even shorter. This in turn is found to increase the liquid flow through the nozzle body and to improve the quality of the liquid atomization.

[0012] For the sake of clarity, it should be noted that in certain prior art spray guns and for certain prior art nozzle bodies, the trajectory of the atomizing air is sometimes also angled away from the spray axis after the atomizing air that was initially directed towards the spray axis has crossed the spray axis. In those prior art devices, however, the atomizing air is not directed away from the spray axis at the moment the atomizing air exits the atomizing air outlet, and the atomizing air is not directed away from the spray axis in the immediate vicinity of the atomizing air outlet. In contrast to such conventional spray guns and conventional nozzle bodies, in the spray gun and nozzle body according to the present disclosure, the atomizing gas is directed away from the spray axis at the moment the atomizing gas exits the atomizing gas outlet, and the atomizing gas is directed away from the spray axis in the immediate vicinity of the atomizing gas outlet.

[0013] Nozzle bodies are generally known in conventional liquid paint spray guns. The nozzle body generally comprises a nozzle having a nozzle opening through which the liquid to be sprayed exits the nozzle body into the outside air. Specific conventional nozzle bodies are described, for example, in PCT patent application WO 2012 / 109298 Al or WO 2013 / 016474 Al.

[0014] As with conventional nozzle bodies, in use, the nozzle body according to the present disclosure is generally connected to a barrel of a spray gun, such as a barrel holding a paint cup, or to a body of a spray gun. Liquid is supplied into the nozzle body through the barrel or through the spray gun body. A nozzle port on the barrel or on the spray gun body can be engaged with a corresponding mating barrel port on the nozzle body, so that the liquid to be sprayed can flow from the barrel or the spray gun body through the nozzle port and the barrel port into the nozzle body, and within the nozzle body to the nozzle tube outlet, where the liquid exits the nozzle body and the spray gun.

[0015] The nozzle body according to the present disclosure comprises a nozzle tube having a wall, an inlet, an outlet, and a channel through which liquid flows from the inlet to the outlet. At the nozzle tube outlet, the liquid exits the nozzle body in a spray direction and is atomized close to the nozzle tube outlet by a flow of pressurized gas (“atomizing gas”) to form a fine droplet spray that is propagated through the surrounding air to eventually impact a surface to be coated with the liquid.

[0016] The nozzle body according to the present disclosure is used in a spray gun that sprays a liquid and uses pressurized gas to atomize the liquid. Nozzle bodies and nozzle body assemblies for other types of spray devices, such as electrostatic spray guns or spray guns for spraying solids, are outside the scope of the present disclosure.

[0017] As used herein, the term "liquid" refers especially to liquid paints, such as those including pigments or other suspended particles or dyes, liquid primers, and liquid clear coats, liquid lacquers, liquid base coats, or liquid varnishes. The liquid can be colored or colorless. Liquid paints are, for example, those used in automotive repair shops for coating surfaces of vehicle parts. In general, as used herein, "liquid" refers to liquid coating materials that can be applied to a surface using a spray gun system, including (but not limited to) paints, primers, base coats, lacquers, varnishes, and similar coating materials, as well as other materials such as adhesives, sealants, fillers, putties, grinding pastes, release agents, and foundry dressings, which can be applied in atomized form depending on the properties of the material and / or the intended application. Liquids according to the present disclosure can include a carrier liquid and solid particles (pigments, powders, fines, etc.) suspended in the carrier liquid.

[0018] As used herein, a substance is considered to be a liquid if its viscosity at 20 °C is less than about 20,000 mPa.s, and especially if its viscosity at 20 °C is less than about 2,000 mPa.s.

[0019] Most conventional spray guns use pressurized air to atomize the liquid and shape the spray jet. However, other gases and mixtures of gases are sometimes used for these purposes. As used herein, the term "gas" refers to a gas, such as nitrogen, oxygen, argon, carbon dioxide, or helium, as well as mixtures of gases, such as air. The use of "air" in conventional technical terms such as "air cap" for a component of a spray gun does not exclude the availability of the component with another gas mixture or with another gas.

[0020] The nozzle body according to the present disclosure includes an elongated nozzle tube having a wall ("nozzle tube wall"), an inlet ("nozzle tube inlet"), an outlet ("nozzle tube outlet"), and a passage ("nozzle tube passage"). The nozzle tube can be a tubular element of any length. The nozzle tube can be, for example, a tubular element of a length of 2 millimeters (mm) or 5 mm or 10 mm.

[0021] The nozzle tube is elongated, extending in a length direction. The length direction of the nozzle tube defines an axial direction of the nozzle tube and the nozzle body. The radial direction is a direction orthogonal to the axial direction.

[0022] The nozzle tube can have a cross-section. The cross-section is not particularly limited. The nozzle tube can have, for example, a circular cross-section or an elliptical cross-section. The nozzle tube can have an irregular (e.g., asymmetric) cross-section in at least a longitudinal section of the elongated nozzle tube. The nozzle tube can have, for example, a cross-section that varies in its length direction, such as from a circular cross-section to an elliptical cross-section.

[0023] In certain embodiments, the tubular nozzle tube is straight, i.e., it is a straight tubular element. In certain embodiments, the nozzle tube is a straight tubular element having the same circular cross-section along its length. In other embodiments, the nozzle tube is bent or curved. In certain embodiments, the nozzle tube comprises a straight axial section. In some of these embodiments, the straight axial section comprises the nozzle tube outlet.

[0024] The nozzle tube is tubular. By “tubular” is meant the shape of a tube, as commonly known, for example a cylindrical tube, such as a straight tube having a circular cross-section; a curved tube, such as an S-shaped tube; or a deformed tube. The tube is considered to be hollow and comprises a tube wall herein. In a deformed tube, the tube wall has an irregular shape or an irregular cross-section.

[0025] The nozzle tube can be connected, for example at the nozzle tube inlet, to a paint guiding element for guiding the liquid to the nozzle tube.

[0026] The nozzle tube comprises a nozzle tube channel extending between the nozzle tube inlet and the nozzle tube outlet for guiding the liquid from the nozzle tube inlet to the nozzle tube outlet. The nozzle tube inlet is a first end of the nozzle tube channel. The nozzle tube outlet is a second end of the nozzle tube channel opposite the first end.

[0027] The nozzle tube channel can have a cross-section. The cross-section can not be particularly limited. The nozzle tube channel can have, for example, a circular cross-section or an elliptical cross-section or an irregularly shaped cross-section.

[0028] In certain embodiments, the nozzle tube channel is straight between the nozzle tube inlet and the nozzle tube outlet. In certain embodiments, the nozzle tube channel is a straight cylindrical space having the same circular cross-section along its length. In certain embodiments, the nozzle tube channel comprises a straight axial section. In some of these embodiments, the straight axial section comprises the nozzle tube outlet.

[0029] In other embodiments, the nozzle tube channel is curved. In some of these embodiments, the nozzle tube channel comprises a curved section and a straight section. The straight section can comprise the nozzle tube outlet.

[0030] The nozzle tube has a nozzle tube wall. The wall can extend generally longitudinally in the axial direction. The wall can extend to the nozzle tube outlet. The nozzle tube wall can separate the nozzle tube channel from a space outside the nozzle tube, such as from the atomizing gas channel.

[0031] The nozzle tube wall can have a thickness. The thickness can be defined by an extension of the nozzle tube wall in a radial direction. The thickness of the nozzle tube wall can vary along the length of the nozzle tube. Alternatively, the thickness of the nozzle tube wall can be constant along the length of the nozzle tube.

[0032] The nozzle tube wall can have a cross-section, for example a circular or elliptical annular shape cross-section. The shape of the cross-section of the nozzle tube wall can vary along the length of the nozzle tube. Alternatively, the shape of the cross-section of the nozzle tube wall can be equal along the length of the nozzle tube.

[0033] The choice of material or materials of the nozzle tube wall is not particularly limited. The material in contact with the liquid can be chosen to be chemically compatible with the liquid to be sprayed, for example chemically inert with respect to the liquid. In certain embodiments of the nozzle body according to the present disclosure, the nozzle tube wall is made of or comprises a polymeric material or a metal. Polymeric materials can generally be moulded or cast or otherwise formed with high precision at reasonable cost to form a nozzle tube and nozzle tube wall suitable for directing the two portions of pressurised atomising gas and liquid angularly away from the spray axis. Metals are a versatile material that can be machined, metal injection moulded, cast or otherwise formed with high precision at reasonable cost to form a nozzle tube and nozzle tube wall suitable for directing the two portions of liquid and pressurised atomising gas angularly away from the spray axis. Of the group of polymeric materials and the group of metal materials, many suitable materials are known to have chemical properties that do not chemically react with typical liquids, thereby being usable for extended periods of time, making polymeric and metal materials versatile substances for manufacturing nozzle bodies and nozzle tube walls according to the present disclosure.

[0034] The nozzle tube wall comprises a radially inner surface and an opposite radially outer surface. The inner and outer surfaces are separated by a thickness of the nozzle tube wall. The inner surface is oriented radially inwards and faces the nozzle tube passage. The inner surface bounds the nozzle tube passage. In use, the liquid guided by the nozzle tube passage is in contact with the inner surface of the nozzle tube wall.

[0035] The radially outer surface is generally arranged opposite the radially inner surface and radially outward from the inner surface. The outer surface is oriented radially outwards and radially away from the nozzle tube passage. In certain embodiments, the outer surface is concentric with the inner surface.

[0036] In use, the outer surface not only bounds the nozzle tube wall and nozzle tube, but can also bound, in conjunction with another element (for example an element of a gas cap as explained below), an atomising gas passage. In some of such embodiments, the outer surface is in contact with the atomising gas guided through the atomising gas passage towards an atomising gas outlet arranged circumferentially around the nozzle tube wall at the nozzle tube outlet.

[0037] The nozzle tube wall and the nozzle tube passage are radially inboard of the outer surface, while the atomizing gas passage is radially outboard of the outer surface. In such embodiments, the nozzle tube wall is disposed radially between the nozzle tube passage and the atomizing gas passage. The nozzle tube wall separates the nozzle tube passage from the atomizing gas passage.

[0038] The forwardmost axial portion of the outer surface of the nozzle tube wall is the portion that generally has a strong influence on the direction of the pressurized atomizing gas as it exits the atomizing gas outlet. It can therefore be advantageous for this forwardmost portion to be oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis. This forwardmost portion of the outer surface of the nozzle tube wall is the portion at the nozzle tube outlet. Thus, in certain embodiments, the outer surface of the nozzle tube wall at the nozzle tube outlet is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis.

[0039] Similarly, the forwardmost axial portion of the inner surface of the nozzle tube wall is the portion that generally has a strong influence on the direction of the liquid as it exits the nozzle tube outlet. It can therefore be advantageous for this forwardmost portion to be oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis. This forwardmost portion of the inner surface of the nozzle tube wall is the portion at the nozzle tube outlet. Thus, in certain embodiments, the inner surface of the nozzle tube wall at the nozzle tube outlet is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis. In certain embodiments, the outer surface of the nozzle tube wall at the nozzle tube outlet is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis, and the inner surface of the nozzle tube wall at the nozzle tube outlet is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis.

[0040] In the context of these geometric considerations, it should be noted that the forward end of the outer surface of the nozzle tube wall can not be a perfect edge. At small scales, this forward end can have inconsistent shapes, recesses, protrusions, or chamfers, such as can be required by reliable manufacturing processes for the nozzle tube or are unavoidable in industrial production processes. Such defects or chamfers of axial extension of 0.4 mm or less, regardless of their orientation or shape, are not considered suitable to significantly affect the flow of atomizing gas in a desired manner. Thus, such unavoidable inconsistencies or essential chamfers at the forward end of the outer surface of the nozzle tube wall are not considered herein to be portions of the outer surface of the nozzle tube wall at the nozzle tube outlet.

[0041] The nozzle tube inlet can be shaped as a liquid nozzle port such as can be directly or indirectly connected to a barrel on the spray gun body. Direct connection is a connection where the nozzle tube inlet is in surface contact with the liquid nozzle port, while indirect connection is a connection where an intermediate element connects the nozzle tube inlet with the liquid nozzle port. The connection of the nozzle tube inlet with the liquid nozzle port on the barrel will allow liquid to flow from the barrel or from the spray gun body, as the case can be, into the nozzle body and through the nozzle tube passage to the nozzle tube outlet where the liquid exits the nozzle body into the surrounding air and is atomized by the atomizing gas.

[0042] The nozzle tube outlet is the hole in the nozzle tube through which the liquid exits the nozzle tube (and nozzle body) and into the surrounding air. The nozzle tube outlet is one end of the nozzle tube passage and is in the radial direction bounded by the nozzle tube wall that extends up to the nozzle tube outlet.

[0043] The nozzle tube outlet can have a cross-section. The cross-section of the nozzle tube outlet determines the cross-section of the liquid flow as it exits the nozzle tube and enters the surrounding air before the liquid is atomized to form tiny droplets. While in most embodiments the cross-section of the nozzle tube outlet has a circular shape, in other embodiments it can have other shapes such as an oval shape, a square shape, a rectangular shape, a polygonal shape, or a star shape.

[0044] The nozzle tube outlet can be an orifice in the nozzle body that is circumferentially bounded by the forwardmost (in the spray direction) terminal edge of the inner surface of the nozzle tube wall.

[0045] The cross-section of the nozzle tube outlet can be symmetric about the center point or center of the nozzle tube outlet. The cross-section of the nozzle tube outlet can be rotationally or axially symmetric about the center point or center of the nozzle tube outlet. The cross-section of the nozzle tube outlet can be irregularly shaped, e.g. a shape that does not exhibit symmetry.

[0046] To define the center point or center of the nozzle tube outlet in the most general way, the well-known concept of "centroid" is applied. The centroid of a planar figure, such as the cross-section of the nozzle tube outlet that is perpendicular to the spray direction, is generally known as the arithmetic mean position of all points in the surface of the figure. In geometric shapes one often assumes a uniform mass density, in which case the centroid of a planar figure coincides with the center of mass. Informally, the centroid can be understood as the point where a cutout of the shape of the planar figure (with a uniformly distributed mass) would be perfectly balanced on the tip of a pin.

[0047] The liquid exits the nozzle tube at the nozzle tube outlet into the external air in a spraying direction. The spraying direction is the direction of flight of the liquid stream at the exact location where the liquid leaves the nozzle tube channel. This location is the location at the nozzle tube outlet, i.e. in the foremost part of the nozzle tube wall near the nozzle tube outlet. Depending on the case, further downstream the liquid stream can no longer have a well-defined direction of flight. Therefore, the definition of "spraying direction" herein is based on the direction of the liquid stream at the location where the liquid leaves the nozzle tube channel.

[0048] The spraying direction is generally determined by the orientation of the terminal part of the nozzle tube channel, i.e. the part closest to the nozzle tube outlet. When the liquid exits the nozzle tube channel into the external air, a part of the liquid is directed angularly away from the spraying axis, other parts can exit the nozzle tube outlet in a direction parallel to the spraying axis. Therefore, not all parts of the liquid have the same direction of flight when leaving the nozzle tube channel into the external air. The term "spraying direction" refers to the general orientation of the liquid jet as a whole when it leaves the nozzle tube outlet. If necessary to determine the spraying direction, it can be calculated as the average direction of flight of the liquid jet when it leaves the nozzle tube outlet. Generally, the spraying direction of the liquid jet is parallel to the spraying axis.

[0049] The spraying direction through the centroid of the cross-section of the nozzle tube outlet defines the spraying axis. Therefore, the spraying axis always passes through this centroid. In most embodiments, the direction of the spraying axis is an axial direction. The axial direction is defined by the length direction of the nozzle tube channel. In case the nozzle tube channel is not straight, its length direction is the direction passing through the centroid of the nozzle tube inlet and the centroid of the nozzle tube outlet.

[0050] The nozzle tube outlet is arranged around the spraying axis and comprises the spraying axis. In a preferred embodiment, the nozzle tube outlet has a circular cross-section, i.e. the cross-section of a disc, centered on the spraying axis. In contrast to a nozzle tube outlet having an annular cross-section, the nozzle tube outlet of the nozzle body according to the present disclosure comprises the spraying axis. In such a nozzle tube outlet, the liquid exits the nozzle tube channel through the nozzle tube outlet at the location of the spraying axis. This geometry can help to obtain a liquid jet having a smaller diameter and thereby can provide a more consistent spray pattern. Moreover, the resulting liquid jet has a smaller outer surface than e.g. a jet forming a hollow cylindrical curtain. The smaller outer surface reduces the evaporation of the liquid.

[0051] At a short distance downstream from the location where the liquid exits the nozzle tube passage through the nozzle tube outlet, the liquid jet is atomized by the flow of atomizing gas. Unlike the geometry of the flow of atomizing gas in conventional nozzle bodies, the nozzle body according to the present disclosure directs at least a portion of the atomizing gas and a portion of the liquid angularly away from the spray axis. The "diverging" atomizing gas can not directly impinge on the diverging liquid jet emanating from the nozzle tube outlet. Rather, the diverging atomizing gas will form a larger decompression zone located directly in front of the nozzle tube outlet, i.e. downstream of the nozzle tube outlet. The combination of the diverging atomizing gas and the diverging liquid of the present invention results in a shorter decompression zone in front of the nozzle body, which helps to improve the atomization quality and to increase the liquid flow without having to increase the atomizing gas pressure. In certain configurations, the divergence of the atomizing gas can also enhance the turbulence in front of the decompression zone. Without wishing to be bound by this theory, the inventors believe that this stronger turbulence helps to achieve a more efficient atomization of the liquid, while the larger decompression zone helps to increase the liquid flow.

[0052] The flow direction of the atomizing gas can be determined by the orientation and / or shape of the outer surface of the nozzle tube wall alone or in combination with another surface of the nozzle body. However, in many known spray gun designs, such as in certain spray gun designs shown in international patent application published as WO 2012 / 109298 A1, the flow direction of the atomizing gas is determined by the orientation and / or shape of the outer surface of the nozzle tube wall and by the orientation and / or shape of a surface of the gas cap. Gas caps are generally known in many existing spray guns: the gas cap is an element that is directly or indirectly attached to the barrel or body of the spray gun and directs pressurized gas in a suitable direction to atomize a liquid jet and to shape a jet of tiny droplets of the atomized liquid. Certain gas caps are provided with a gas horn having shaped air holes to direct so-called shaping gas from opposite directions towards the atomized liquid jet in order to shape the spray jet into a desired pattern. The gas cap and the nozzle body can be integrated to form an integrated gas cap / nozzle body, for example as described in European patent EP 2736651 B1.

[0053] When the gas cap is directly or indirectly connected with the nozzle body, the outer surface of the nozzle tube wall can operate in combination with a surface of the gas cap to form an atomizing gas outlet arranged circumferentially around the nozzle tube outlet. The atomizing gas outlet can be formed between the surface of the gas cap and the outer surface of the nozzle tube wall at the nozzle tube outlet, i.e. the outer surface of the tip of the nozzle tube.

[0054] The circumferential arrangement of the atomizing gas outlet around the nozzle tube outlet is not limited to a circular circumferential arrangement, but includes for example an elliptical circumferential arrangement, a square or rectangular or other polygonal circumferential arrangement, a star-shaped circumferential arrangement and an irregularly shaped circumferential arrangement. The atomizing gas outlet can have an annular shape, a circular shape, an elliptical shape, a square shape or a rectangular shape or another polygonal shape, a star shape or an irregular shape.

[0055] While the shape of the circumferential arrangement is not particularly limited, it is preferred that the atomizing gas outlet forms substantially the entire circumference around the nozzle tube outlet, whatever the shape. This helps to ensure proper atomization of the liquid.

[0056] The width of the atomizing gas outlet is not particularly limited. The width is the extension of the atomizing gas outlet in the radial direction in the plane of the nozzle tube outlet. In certain configurations, the width is the radial distance from the outer surface of the nozzle body to the edge of the nozzle hole in the plane of the nozzle tube outlet. For example, the atomizing gas outlet can have a width between 0.01 millimeter (mm) and 5.00 mm. Preferably, the atomizing gas outlet has a width between 0.1 millimeter (mm) and 1.00 mm. A wider atomizing gas outlet will result in lower gas velocity at a given atomizing gas pressure, thus resulting in a reduced shear stress / velocity gradient between the gas and the liquid to be atomized. In contrast, a narrower atomizing gas outlet allows less gas to pass, but this gas can flow at a higher velocity, thus increasing the shear stress between the gas and the liquid. The preferred width is chosen in a large set of design parameters (desired air consumption, desired liquid flow, atomization quality, etc.) to help achieve an acceptable balance between these effects.

[0057] The atomizing gas outlet can be circumferentially arranged around the nozzle tube outlet at a radial distance from the nozzle tube outlet. This radial distance can be the thickness of the nozzle tube wall at the end of the nozzle tube, i.e. at the nozzle tube outlet. At the nozzle tube outlet, the radial distance between the nozzle tube outlet and the atomizing gas outlet can be between 0.01 mm and 5 mm, preferably between 0.1 mm and 1 mm. As the gas exit velocity is typically highest at the atomizing gas outlet and decays as it moves downstream, it can be beneficial to place the nozzle tube outlet as close as practically possible to the gas outlet. One way to do this is by minimizing the radial distance between the nozzle tube outlet and the atomizing gas outlet. Generally, a larger radial distance results in lower extraction and atomization efficiency of the liquid. In contrast, a smaller radial distance can result in the nozzle tube wall being very thin at the nozzle tube outlet, thus introducing a risk of inconsistency and damage.

[0058] The nozzle tube outlet can be arranged in a geometric plane, such as a plane orthogonal to the spray axis or orthogonal to the axial direction. The atomizing gas outlet can be arranged in the same geometric plane as the nozzle tube outlet, or it can be recessed or protrude up to 5 mm from the plane of the nozzle tube outlet.

[0059] The outer surface of the nozzle tube wall is further operable to, in conjunction with a surface of the gas cap when the gas cap is directly or indirectly connected with the nozzle body, form an atomizing gas passage for directing pressurized atomizing gas towards the atomizing gas outlet. Thus, pressurized atomizing gas can exit the atomizing gas passage into the external air at the atomizing gas outlet and can atomize the liquid after the liquid has exited the nozzle tube outlet.

[0060] Thus, a first portion of the atomizing gas passage can be formed by a surface of the gas cap, while a second portion of the atomizing gas passage can be formed by the outer surface of the nozzle tube wall. Prior to the connection of the gas cap with the nozzle body, the atomizing gas passage is thus not present or is incomplete in that it is not properly defined such that pressurized atomizing gas is not directed towards the atomizing gas outlet. However, once a suitable gas cap is connected, the outer surface of the nozzle tube wall is adapted (properly shaped, properly arranged, having a suitable surface structure) to form a portion of the atomizing gas passage without the gas cap.

[0061] A suitable gas cap can be directly or indirectly connected with a nozzle body according to the present disclosure. Two elements are considered to be "directly connected" herein if they are connected without an intermediate element and are in surface contact with each other. Two elements are considered to be "indirectly connected" herein if they are connected with each other via an intermediate element, regardless of whether they are in surface contact with each other.

[0062] A nozzle body as described herein in combination with a gas cap can form a nozzle assembly. In a nozzle assembly or otherwise, the gas cap can be connected in a fixed spatial relationship with the nozzle body. The fixed spatial relationship can help to keep the shape of the atomizing gas outlet formed between a portion of the gas cap and the nozzle tube wall constant. The nozzle assembly can be attached to a platform of a spray gun, such as by attaching the nozzle body to the spray gun platform or by attaching the gas cap to the spray gun platform or both.

[0063] In certain of these nozzle assemblies, the nozzle assembly comprises a nozzle body as described herein, and a gas cap connected in a fixed spatial relationship with the nozzle body, wherein the gas cap comprises a front wall facing generally in the spray direction and comprising a nozzle hole bounded by a nozzle hole edge, and wherein the nozzle tube is arranged in or projects outwardly through the nozzle hole such that the atomizing gas outlet is formed between the nozzle hole edge and the nozzle tube wall.

[0064] Optionally, the gas cap further comprises two gas horns arranged opposite each other with respect to the spray axis, each gas horn comprising a shaping gas hole for directing shaping gas to act on the atomized liquid exiting the nozzle tube outlet into the external air in the spray direction.

[0065] The nozzle assembly of this kind has the advantage that the radially inner limit of the atomizing gas outlet is formed by the nozzle tube wall and the radially outer limit of the atomizing gas outlet is formed by the nozzle hole edge. Thus, a nozzle body directing a portion of the atomizing gas at a certain angle angularly away from the spray axis can be used with different geometrical gas caps. This in turn allows for a variation of the geometry of the atomizing gas outlet, e.g. its width or its orientation, just by utilizing different gas caps without having to change the nozzle body.

[0066] The front wall of the gas cap is an outer wall of the gas cap comprising a front surface facing generally forward, i.e. generally towards the spray direction. The front surface is typically in contact with the outside air. The front wall can be a wall of the gas cap, a portion of which can be arranged between opposite gas corners, if such gas corners are present.

[0067] The front wall can form a nozzle hole in which the front end of the nozzle tube can be arranged or through which the front end of the nozzle tube protrudes outward. The edge in the front wall delimiting the nozzle hole is referred to herein as the nozzle hole edge. In use, the gas cap comprising its front wall is arranged with the spray axis as a center. The nozzle hole can be arranged with the spray axis as a center and concentric with the nozzle tube outlet. In the plane of the nozzle tube outlet, there can be a gap between the nozzle tube and the nozzle hole edge. The gap can extend circumferentially to form a circle. The width of the gap extends in the radial direction. The gap can form the atomizing gas outlet described herein. The atomizing gas outlet is arranged circumferentially around the nozzle tube outlet such that the pressurized atomizing gas exits through the atomizing gas outlet and into the outside air and atomizes the liquid after the liquid has exited the nozzle tube outlet.

[0068] In the nozzle body and nozzle assembly described herein, the first portion of the atomizing gas is directed angularly away from the spray axis by the orientation or shape of the outer surface of the nozzle tube wall upon exiting the atomizing gas outlet. In the nozzle assembly as described in the preceding paragraph, the gas cap can help direct a further second portion of the atomizing gas angularly away from the spray axis via the appropriately shaped or oriented nozzle hole edge. This can further enhance the liquid extraction and liquid atomization provided by the direction of the first portion of the atomizing gas away from the spray axis. The improved atomization can alternatively allow for a reduction of the atomizing gas pressure, which can help reduce the generation of high frequency noise in which a human operator is exposed.

[0069] Accordingly, in certain embodiments of the nozzle assemblies described above, the nozzle orifice edge is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis. The nozzle orifice edge may, for example, be tilted radially outwardly relative to the spray axis, such as to form a diverging conical surface. In other words, the nozzle orifice edge can have a larger diameter (or enclose a larger area) at a downstream axial location than at a more upstream axial location. Tilting outwardly, for example, draws a portion of the atomizing gas away from the spray axis via aerodynamic effects.

[0070] For a target surface to be uniformly covered, it is generally desirable to obtain a liquid spray jet that is perfectly rotationally symmetric relative to the spray axis. To approach a symmetric liquid jet, in certain embodiments of the nozzle bodies described herein, the nozzle tube outlet and / or the nozzle tube wall have a rotationally symmetric shape and are arranged concentrically with each other, such as centered on the spray axis. Similarly, the entire gas cap and / or the nozzle orifice edge can have a rotationally symmetric shape and can be arranged concentrically with each other, such as centered on the symmetry axis of the gas cap.

[0071] To approach a symmetric liquid jet even more, in certain embodiments of the nozzle assemblies described herein, the nozzle tube outlet, the nozzle tube wall, the nozzle orifice edge, and the atomizing gas outlet each have a rotationally symmetric shape and are arranged concentrically relative to the spray axis.

[0072] Certain liquid spray guns have a cartridge attached to the gun platform through which the liquid to be sprayed flows from an external container into the gun. After a spraying operation, only the liquid of the cartridge and the nozzle body need to be cleaned without cleaning the gun platform. The rear of the cartridge is attached to the gun platform, while its front is typically used to attach the gas cap and the nozzle body. Another function of the cartridge is to guide pressurized gas from the gun platform to the atomizing gas outlet and potentially to a shaping gas outlet (e.g., in a gas horn) towards the front of the gun. The cartridge can include separate conduits for the atomizing gas and the shaping gas. In some embodiments, the cartridge and the nozzle body are integrally formed as a single component.

[0073] A nozzle assembly including a gas cap and a nozzle body according to the present disclosure has been described above. The nozzle body according to the present disclosure can be connected to a spray gun body in use, but is alternatively connected to a cartridge body attached to the spray gun body. The gas cap can also be connected to the spray gun body, but the gas cap can alternatively be connected to the cartridge body attached to the spray gun body. In the case that the gas cap and the nozzle body are each connected to the cartridge body, these connections to the cartridge body can help establish and maintain a fixed spatial relationship between the nozzle body and the gas cap. This fixed spatial relationship helps maintain the shape and orientation of the atomizing gas outlet formed between a portion of the gas cap (e.g., its nozzle hole edge) and a portion of the nozzle body (its nozzle tube wall) constant. Maintaining the shape and orientation of the atomizing gas outlet helps maintain the atomizing liquid jet in a consistent fixed geometry and helps atomization constant over time.

[0074] Thus, in certain embodiments of the nozzle assemblies described herein, the nozzle assembly further comprises a cartridge body having a liquid port connector for directly or indirectly connecting a liquid reservoir to the cartridge body, wherein the gas cap is connected with the cartridge body and the nozzle body is connected with the cartridge body such that the gas cap is connected with the nozzle body in a fixed spatial relationship.

[0075] The atomizing gas outlet can be formed by a portion of the nozzle tube and a portion of the gas cap. Specifically, at the nozzle tube outlet or at an axial position further upstream, the outer surface of the nozzle tube wall can be operable to join with a surface of the gas cap to form the atomizing gas passage and the atomizing gas outlet at which the atomizing gas exits the atomizing gas passage into the external air and atomizes the liquid after the liquid has exited the nozzle tube outlet.

[0076] In the case that the atomizing gas outlet is formed by the outer surface of the nozzle tube wall and the surface of the gas cap, pressurized atomizing gas can exit the atomizing gas passage into the external air at the atomizing gas outlet. The atomizing gas atomizes the liquid shortly after the liquid exits the nozzle tube outlet. The atomizing gas outlet is disposed circumferentially around the nozzle tube outlet.

[0077] The atomizing gas outlet can be formed by a portion of the nozzle tube and a portion of the gas cap. Specifically, at the nozzle tube outlet or at an axial position further upstream, the outer surface of the nozzle tube wall can be operable to join with a surface of the gas cap to form the atomizing gas passage and the atomizing gas outlet at which the atomizing gas exits the atomizing gas passage into the external air and atomizes the liquid after the liquid has exited the nozzle tube outlet.

[0078] Alternatively, the atomizing gas outlet can be formed solely by the nozzle body. In such embodiments, the atomizing gas outlet is formed without the need for a gas cap or another element to form the atomizing gas outlet.

[0079] The atomizing gas outlet can be an annular (i.e., ring-shaped) atomizing gas outlet. The atomizing gas outlet can be arranged concentrically with the nozzle tube outlet. The atomizing gas outlet can be arranged centered on the spray axis. The nozzle tube outlet and the atomizing gas outlet can be arranged concentrically with each other and centered on the spray axis. The atomizing gas outlet can be arranged concentrically around the nozzle tube outlet, with the atomizing gas outlet and the atomizing gas outlet being arranged centered on the spray axis.

[0080] The atomizing gas outlet can have an annular shape, such as an annular shape centered on the spray axis. The atomizing gas outlet can be radially inwardly bounded by a surface of the nozzle body (e.g., by an outer surface of the nozzle tube wall at the nozzle tube outlet). The atomizing gas outlet can be radially outwardly bounded by a surface of the gas cap (e.g., by a hole-defining surface of a hole in the front wall bounding the gas cap). The annular shape can form a full 360° angle around the spray axis, or, alternatively, one or more circumferential segments of a 360° angle around the spray axis.

[0081] In a nozzle body according to the present disclosure, an outer surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the atomizing gas exiting the atomizing gas outlet angularly away from the spray axis, while an inner surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis. The direction away from the spray axis is also referred to herein as the “divergent” direction, and the property of being directed away from the spray axis is referred to as “divergent” or “diverging”.

[0082] In certain embodiments, the outer surface of the nozzle tube wall has a cylindrical surface portion with its symmetry axis coaxial with the spray axis, and a diverging portion in the vicinity of the nozzle tube outlet (i.e., at the front end portion of the nozzle tube). In its diverging portion, the outer surface of the nozzle tube wall can have a diameter that linearly increases with decreasing axial distance to the nozzle tube outlet. In a longitudinal section through the center of the nozzle tube passage, the profile of the outer surface of the nozzle tube wall in the diverging portion can be a straight line that rises with decreasing axial distance to the nozzle tube outlet. In some embodiments, the outer surface of the nozzle tube wall in its diverging portion can have a diameter that exponentially, polynomially, parabolically, or hyperbolically increases with decreasing axial distance to the nozzle tube outlet.

[0083] In other embodiments, in a longitudinal section through the center of the nozzle tube passage, the profile of the outer surface of the nozzle tube wall in the diverging portion can be a segment of a circle or a segment of an ellipse.

[0084] In certain embodiments, the outer surface of the nozzle tube wall includes a slanted axial segment, such as a slanted axial segment at the nozzle tube outlet, for directing at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis. The term "slanted" refers herein to a representation of the outer surface in a longitudinal section of the nozzle body that passes through the spray axis, where a line representing the "slanted" axial segment of the outer surface is slanted relative to the spray axis. With the slanted orientation, the outer surface can direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis.

[0085] The slanted axial segment can be located at the nozzle tube outlet or upstream of the nozzle tube outlet. If located upstream of the nozzle tube outlet, the slanted axial segment must be close enough to the nozzle tube outlet to still direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis.

[0086] The slanted axial segment can have an axial extension of 0.5 millimeter or more, or 1.0 mm or more. A slanted axial segment of this length is considered suitable to affect the flow of atomizing gas in a desired manner.

[0087] The slanted axial segment can be easily manufactured and direct the compressed atomizing gas over an extended axial distance, i.e., along the length of the slanted segment, into a direction that is angularly oriented away from the spray axis. This in turn can help generate a consistent volume of low pressure in front of the nozzle tube outlet, resulting in an increase in liquid, e.g., paint, flow and / or a reduction in consumption of pressurized atomizing gas and / or a reduction in high frequency noise.

[0088] In certain embodiments of a nozzle body according to the present disclosure, the slanted axial segment forms a slant angle (a) with the spray axis, where the slant angle (a) is between 0.5° and 45°. The slant angle a of the outer surface of the nozzle tube wall largely determines the angle between the velocity of portions of the atomizing gas exiting the atomizing gas outlet and the spray axis. In case the atomizing gas exits the atomizing gas outlet at an angle of less than 0.5° relative to the spray axis, the liquid flow will not be significantly greater than the liquid flow when using a conventional nozzle body. In case the atomizing gas exits the atomizing gas outlet at an angle of more than 45° relative to the spray axis, the low pressure region in front of the nozzle tube outlet is considered to be spread too far to have a significant desired effect on liquid flow, consumption of atomizing gas, and noise.

[0089] The inclination angle is a simple means to control the direction of the velocity vector of the atomizing gas at the nozzle tube outlet. A positive inclination angle a imparts a radial component to the velocity vector, such that the velocity vector points angularly away from the spray axis. An inclination angle between 0.5° and 45° causes the atomizing gas to move at a corresponding angle relative to the spray axis. This range of angles of movement of the atomizing gas is considered suitable in many cases to bring about the benefits described above in terms of reduced compressed gas consumption, increased liquid flow, and / or reduced hissing noise.

[0090] A circumferential position is considered to be a position on a closed path, for example extending a full 360° angle around the spray axis in a plane orthogonal to the spray axis and at some (varying or fixed) distance of the spray axis. In case the closed path is a circle, the circumferential position is a position on that circle. Relative to a reference radius, the circumferential position can be a position at some angle.

[0091] In most cases, it is generally desirable to obtain uniform atomization. Therefore, in many embodiments, the above-mentioned inclination angle at a certain axial position is equal at all circumferential positions of the outer surface of the nozzle tube wall. In certain embodiments, however, the inclination angle at a first circumferential position of the outer surface of the nozzle tube wall is different from the inclination angle at a second circumferential position of the outer surface of the nozzle tube wall.

[0092] Different inclination angles of the nozzle tube wall at different circumferential positions at a certain axial position will cause the pressurized atomizing gas to be directed away from the spray axis at different angles. This can be beneficial in cases where it is desired to impart certain geometric properties to the atomized liquid jet or to cause non-uniform atomization.

[0093] In certain embodiments, and irrespective of any specific profile in a longitudinal cross-sectional view, the outer surface of the nozzle tube wall in the diverging portion can be rotationally symmetric about the spray axis. In certain embodiments, and irrespective of any specific profile in a longitudinal cross-sectional view, the outer surface of the nozzle tube wall at the nozzle tube outlet is rotationally symmetric about the spray axis.

[0094] In certain embodiments, the outer surface of the nozzle tube wall comprises a gas directing portion for directing at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis, and wherein the gas directing portion has the shape of a radial outer surface of a truncated cone. Mathematically, a truncated cone is also referred to as a "frustum". A truncated cone defines an axis of symmetry. A radial direction of the truncated cone is a direction orthogonal to the axis of symmetry. An axial end portion of the truncated cone shape having a larger radial extension can be located downstream in the spray direction of an axial end portion of the truncated cone shape having a smaller radial extension.

[0095] The shape of the truncated cone can be simple and cost effective to manufacture on a lathe or in molding with high surface quality. High surface quality means a smooth surface that helps to achieve a consistent flow of atomized gas. By its shape, the conical gas guiding portion of the nozzle tube wall imparts a consistent velocity component to the pressurized atomized gas flowing along the outer surface of the nozzle tube wall and its gas guiding portion, which is directed angularly away from the spray axis.

[0096] As used herein, the axial position at which the liquid exits the nozzle tube passage into the external air is the axial position "at the nozzle tube outlet." Since the nozzle tube wall bounds the nozzle tube passage that terminates at the nozzle tube outlet, this axial position is the axial position at which the nozzle tube wall (and the nozzle tube) terminates. In other words, the nozzle tube wall extends axially upward to the nozzle tube outlet. The outer surface of the nozzle tube wall also terminates at the nozzle tube outlet.

[0097] In a cross-section taken in a plane orthogonal to the spray axis at this axial position (i.e., at the nozzle tube outlet), the cross-section of the outer surface of the nozzle tube wall can be circular. Alternatively, the outer surface can have a different cross-section. In a cross-section taken in a plane orthogonal to the spray axis at this axial position (i.e., at the nozzle tube outlet), the cross-section of the inner surface of the nozzle tube wall can be circular. Alternatively, the inner surface can have a different cross-section. In certain embodiments, in a cross-section taken in a plane orthogonal to the spray axis at this axial position (i.e., at the nozzle tube outlet), the cross-sections of the outer surface and the inner surface of the nozzle tube wall are circular. In a cross-section taken in a plane orthogonal to the spray axis at this axial position (i.e., at the nozzle tube outlet), the outer surface and the inner surface of the nozzle tube wall can be circular and concentric.

[0098] The circular cross-section of the outer surface of the nozzle tube wall is particularly cost effective for manufacturing, for example, on a lathe with high symmetrical accuracy (roundness). Precise circular symmetry can help to provide a circularly symmetric jet of atomized gas, thus providing more uniform and more efficient atomization of the liquid at a short distance downstream of the nozzle tube outlet. This can be advantageous and desirable in certain situations. The circular cross-section can be interrupted by small structural elements that may, for example, help to maintain fixed spatial relationships and a uniform distance between the outer surface of the nozzle tube wall and a gas cap that, in combination with the nozzle tube wall, forms an atomized gas outlet.

[0099] In case the outer surface of the nozzle tube wall at the nozzle tube outlet is circular in a cross-section taken in a plane orthogonal to the spraying axis, the outer surface at the nozzle tube outlet can extend over a full 360° angle in the circumferential direction. A full 360° angle is considered to be related to an uninterrupted circular shape. An uninterrupted circular shape of the outer surface of the nozzle tube wall at the nozzle tube outlet, i.e. at the end of the nozzle tube wall, is particularly cost-effective for manufacturing with high symmetry accuracy (circularity) on a lathe, for example. The uninterrupted 360° circular symmetry can help to provide a circularly symmetric jet of atomized gas, thus providing a more uniform and more efficient atomization of the liquid at a short distance downstream of the nozzle tube outlet. This can be advantageous and desirable in certain cases.

[0100] However, in other embodiments, the outer surface can not be rotationally symmetrical. In certain of these embodiments, in a first angular position measured around the spraying axis, the outer surface of the nozzle tube wall can direct the atomized gas angularly away from the spraying axis at a first angle. In a second angular position measured around the spraying axis, the outer surface of the nozzle tube wall can direct the atomized gas angularly away from the spraying axis at a second, larger angle. The second angular position can be spaced apart from the first angular position by an angle of, for example, 90°, 60°, or 45°.

[0101] In a third angular position measured around the spraying axis, the outer surface of the nozzle tube wall can direct the atomized gas angularly away from the spraying axis at the first angle. The third angular position can be spaced apart from the first angular position by an angle of, for example, 180°, 120°, or 90°.

[0102] When the atomized gas or at least a portion thereof exits the atomized gas outlet, the atomized gas is directed angularly away from the spraying axis by the suitably shaped or oriented outer surface of the nozzle tube wall. The angle at which the atomized gas is directed away from the spraying axis, also referred to herein as the “divergence angle”, can be the same angle in all angular positions around the spraying axis. In such cases, the atomized gas can form a diverging conical shape, interrupted or not interrupted when travelling in the circumferential direction around the spraying axis.

[0103] To obtain good spraying results, the diverging conical shape can be adjusted in response to, for example, a desired coating flow, a desired spraying jet geometry, a viscosity or temperature or solid content of the liquid to be sprayed, an ambient air temperature, or other parameters. To obtain a desired second divergence angle, the first nozzle body providing the atomized gas with a first divergence angle can be replaced by a second nozzle body providing the atomized gas with a second divergence angle.

[0104] In certain embodiments, the divergence angle varies with the angular position around the spray axis. To illustrate this, in the case where the spray axis is oriented horizontally, the divergence angle can be larger in the vertically upward angular position around the horizontal spray axis (“12 o’clock angular position”) and smaller in the vertically downward angular position around the horizontal spray axis (“6 o’clock angular position”).

[0105] The radially inner surface of the nozzle tube wall is oriented or shaped to direct a portion of the liquid exiting the nozzle tube outlet angularly away from the spray axis. In certain embodiments, the radially inner surface of the nozzle tube wall is shaped to diverge towards the nozzle tube outlet. The radially inner surface can be shaped to diverge, for example, in a linear, parabolic, hyperbolic, or exponential fashion. In other words, in a longitudinal cross-section of the nozzle body, the inner surface would appear to follow a linear, parabolic, hyperbolic, or exponential curve. The diverging shape is simple to design and forms directly and cost-effectively in molding, machining, and other types of manufacturing.

[0106] The diverging shape of the inner surface can form a funnel that widens with increasing axial distance from the nozzle tube inlet and that has its widest opening at the nozzle tube outlet. The funnel can be rotationally symmetric with respect to the spray axis, but the funnel can have other shapes. The narrow end of the funnel can be located at a distance of between 0.5 mm and 10 mm behind the nozzle tube outlet.

[0107] In certain embodiments, the inner surface of the nozzle tube wall is oriented parallel to the outer surface of the nozzle tube wall at the nozzle tube outlet. Such a geometry is particularly straightforward to manufacture. The geometry can result in a parallel trajectory of a radially inner portion of the atomizing air and some radially outer portion of the liquid over a short distance. This parallel flow in turn can result in a short path of laminar flow and less turbulence, with some of the liquid being atomized further away from the nozzle tube outlet, which can be desirable in particular applications.

[0108] However, in other embodiments, the inner surface of the nozzle tube wall is oriented at an angle (as opposed to parallel) to the outer surface of the nozzle tube wall at the nozzle tube outlet. The angle can be measured, for example, in a longitudinal cross-sectional view of the nozzle body, where the inner surface would appear as a line forming a certain first angle with the spray axis and the outer surface would appear as a line forming a certain second angle different from the first angle with the spray axis. In such cases, the outer surface of the nozzle tube wall has a different angle of inclination and the inner surface has a different angle of opening, parallel flow of portions of the atomizing gas and the liquid is less likely, and therefore turbulence can be generated earlier at the boundary, potentially resulting in earlier turbulent interaction between the atomizing gas and the liquid. Thus, atomization can start closer to the nozzle tube outlet, which can be desirable in certain cases.

[0109] At the nozzle tube outlet, the inner surface of the nozzle tube wall can be conical, i.e. in the shape of a cone. The apex of the cone is located rearward (upstream) of the nozzle tube outlet. The cone defines an opening angle of the nozzle tube outlet. The opening angle is the angle between the spray axis and the inner surface of the nozzle tube wall at the nozzle tube outlet. In certain embodiments of the nozzle body according to the present disclosure, the opening angle is between 0.5° and 70°, preferably between 10° and 50°.

[0110] The nozzle body according to the present disclosure can be operable to form part of an atomizing gas channel. The nozzle body according to the present disclosure can be operable to form part of an atomizing gas outlet, which is arranged circumferentially around the nozzle tube outlet. In case the atomizing gas outlet has an annular shape, the atomizing gas emitted from the atomizing gas outlet can form a diverging gas curtain. In case the atomizing gas outlet has an annular shape and is centered on the spray axis, the atomizing gas emitted from the atomizing gas outlet can form a diverging gas curtain centered on the spray axis. In case the atomizing gas exits the atomizing gas outlet, the diverging gas curtain can extend a full 360° circle around the spray axis, thereby forming a diverging continuous gas curtain. Alternatively, the diverging gas curtain can extend one or more respective angular segments of a full 360° circle around the spray axis, such as two angular segments of each 90° angle.

[0111] In certain embodiments, the outer surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis at an angle of between 0.5° and 45°. As described above, in case the atomizing gas exits the atomizing gas outlet at an angle of less than 0.5° relative to the spray axis, the liquid flow will not be significantly greater than when using a conventional nozzle body. In case the atomizing gas exits the atomizing gas outlet at an angle of more than 45° relative to the spray axis, the decompression zone in front of the nozzle tube outlet is considered to be spread too far to have a significant desired effect on liquid flow, atomizing gas consumption and noise. In certain of these embodiments, the outer surface of the nozzle tube wall is oriented or shaped to direct at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet angularly away from the spray axis at an angle of between 5° and 15°. The desired effects of higher liquid flow and / or reduced pressurized atomizing air consumption and / or less high-frequency noise are more pronounced in the 5° to 15° angle range.

[0112] According to this disclosure, the nozzle body can be connected to the spray gun platform directly or via its connection to a cylinder connected to the spray gun platform to form a liquid spray gun that directs at least a portion of the pressurized atomizing gas exiting the atomizing gas outlet at an angle away from the spray axis. This angular direction away from the spray axis more effectively utilizes the prime mover of the compressed atomizing gas to extract and atomize the liquid using a lower gas pressure. Alternatively, this effect can be used to consume less pressurized atomizing gas while still maintaining a comparable liquid flow rate achieved by conventional (non-angular) geometry.

[0113] Therefore, this disclosure also provides a liquid spray gun for spraying liquids, the liquid spray gun including a nozzle body as described herein or a nozzle assembly as described herein.

[0114] The nozzle bodies according to this disclosure can be manufactured using conventional manufacturing processes, such as machining or molding. These nozzle bodies can also be made using a 3D printer via additive manufacturing processes. Digital data describing the nozzle body can be stored on a machine-readable medium and sent by a digital processor to a 3D printer, causing the 3D printer to "print" the nozzle body.

[0115] Therefore, this disclosure also provides a non-transitory machine-readable medium storing data representing a three-dimensional model of a nozzle body as described herein or a three-dimensional model of a nozzle assembly as described herein, the data being formatted for access by one or more digital processors docked with a 3D printer, wherein the one or more digital processors are operable to cause the 3D printer to manufacture the nozzle body or the nozzle assembly, respectively.

[0116] The invention will now be described in more detail with reference to the accompanying drawings, which illustrate specific embodiments of the invention by way of example:

[0117] Figure 1 This is an exploded perspective view of a spray gun including a first nozzle body according to the present disclosure;

[0118] Figure 2 This is a perspective view of the first nozzle body attached to the cylinder;

[0119] Figure 3 It includes Figure 2 A perspective view of the nozzle assembly of the first nozzle body and cylinder;

[0120] Figure 4 yes Figure 3 Longitudinal cross-sectional view of the nozzle assembly;

[0121] Figure 5 yes Figures 1 to 4 A longitudinal cross-sectional view of the front part of the first nozzle body;

[0122] Figure 6 is Figure 3 and Figure 4 a longitudinal cross-sectional view of respective front portions of a first nozzle body and a gas cap of a spray tip assembly;

[0123] Figure 7 is a longitudinal cross-sectional view of respective front portions of a first nozzle body and an alternative gas cap of a spray tip assembly;

[0124] Figure 8A is an atomizing gas pressure plot for a conventional nozzle body;

[0125] Figure 8B is an atomizing gas pressure plot for a nozzle body according to the present disclosure, and

[0126] Figure 9 is a plot illustrating liquid flow for a conventional nozzle body versus liquid flow for a nozzle body according to the present disclosure.

[0127] Figure 1 is an exploded perspective view of one illustrative embodiment of a liquid spray gun including a nozzle body as described herein. The liquid spray gun has various components, including a liquid spray gun platform 10 and a spray tip assembly 20 that is releasably attached to the liquid spray gun platform 10, preferably at a barrel interface 11. The spray tip assembly 20 provides features that control movement of both the liquid to be sprayed (e.g., a liquid paint) and the atomizing gas (e.g., air) used to atomize the liquid, as described herein. In some embodiments, the spray tip assembly 20 is disposable and can be discarded after use (although in some cases can be recycled). In some embodiments, if discarded after use, cleaning of the spray tip assembly 20 can be avoided, and the spray gun can be conveniently replaced by, for example, attaching a different spray tip assembly 20 connected to the same or a different liquid container. Connection of the spray tip assembly 20 to the barrel interface 11 of the spray gun platform 10 can be achieved by any suitable technique. For example, connection structures on the spray tip assembly 20 can cooperate (e.g., mechanically interlock) with openings 11a and 11b at the barrel interface 11 to retain the spray tip assembly 20 on the spray gun platform 10.

[0128] Figure 1The depicted spray gun platform 10 defines multiple cavities that together form a channel for delivering gas to the nozzle assembly 20. Among other features, the spray gun platform 10 includes a fitting 12 such that the gas supply channel in the spray gun platform 10 can be connected to a gas source (not shown) that supplies gas to the spray gun platform 10 at a pressure greater than atmospheric pressure. A needle channel is also provided in the spray gun platform 10 to allow a needle 14 to enter the nozzle assembly 20 attached to the barrel interface 11. In the depicted embodiment, control of both the gas flow and the liquid flow through the liquid spray gun is provided by a trigger 15, which is pivotally engaged with the spray gun platform 10 via a retaining pin 16a and a clip 16b. The needle 14 extends through the nozzle assembly 20. The trigger 15 is preferably biased to a non-operating position, in which the needle 14 closes the liquid nozzle opening in the nozzle assembly 20 and also closes the gas supply valve 17. When trigger 15 is pressed, needle 14 retracts to its tapered tip 14a, allowing liquid to flow through the liquid nozzle outlet in the nozzle assembly 20. Simultaneously, gas supply valve 17 opens to deliver gas from the passage in the spray gun platform 10 to the nozzle assembly 20. The gas and liquid flow can be further controlled by a fan gas control assembly 18a and an atomizing gas control assembly 18b. The fan gas control assembly controls the gas delivered from the gas supply manifold in the platform 10 to the fan gas passage outlet 19a and the atomizing gas outlet 19b. The atomizing gas control assembly limits how far trigger 15 can be pressed, thereby limiting the total flow of gas and paint. Specifically, control assembly 18b controls the atomized gas / liquid flow from the nozzle assembly 20, and control assembly 18a controls the gas flow towards the nozzle assembly 20 at an air angle (if provided) to adjust the spray pattern geometry.

[0129] The nozzle assembly 20 includes a cylinder 30, an air cap 40 attached to the cylinder 30, and a nozzle body 1 according to the present disclosure, the nozzle body being attached to a nozzle port on the cylinder 30. The nozzle body 1 may be as follows: Figure 1 The individual components shown can be combined with the air cap 40 to form an integrated air cap / nozzle body. Although Figure 1 An embodiment of a nozzle body 1 with a specific shape is illustrated, but other nozzle bodies according to this disclosure may have other shapes. A nozzle body according to this disclosure may, for example, include an orifice plate having holes for guiding pressurized atomizing gas and / or pressurized shaping gas. A nozzle body according to this disclosure may, for example, include external or internal threads for attaching the nozzle body to a cylinder or spray gun body, while other nozzle bodies according to this disclosure do not have threads but are attached to a cylinder or spray gun body by clamping or other mechanisms.

[0130] Figure 2A nozzle body 1 according to the present disclosure is illustrated in perspective view, when this nozzle body is attached to a barrel 30 which in turn will be attached at its rear part 38 at a barrel interface 11 to a liquid spray gun platform 10. The barrel 30 has a liquid inlet 73 through which liquid is directed into the barrel 30 and towards the nozzle body 1. A liquid port connector 74 at the end of the liquid inlet 73 is formed as a connector structure via which a liquid container (not shown), such as a liquid paint cup, can be connected to the barrel 30. Liquid can flow from the liquid container through the liquid inlet 73 and a liquid passage in the barrel 30 into a nozzle tube passage of the nozzle body 1. The liquid is sprayed through a circular nozzle tube outlet 52 in front of the nozzle body 1 and in a spray direction 300 out of the nozzle tube passage into the external air along a spray axis 200 through the centre of the nozzle tube outlet 52. The nozzle body 1 is rotationally symmetrical about the spray axis 200.

[0131] The barrel 30 and the nozzle body 1 are shown before a gas cap 40 is arranged over the front part 36 of the barrel 30, so that the atomizing gas passage 33 in the barrel 30 is visible, through which pressurized atomizing gas flows through the barrel 30 towards the nozzle tube outlet 52.

[0132] Once a suitable gas cap 40 is mounted over the front part 36 and the nozzle body 1, the inner surface of the gas cap 40 and the outer surface 75 of the nozzle body 1 cooperate to form an atomizing gas passage for guiding pressurized atomizing gas towards the atomizing gas outlet 54 (see Figure 3 ) which is arranged circumferentially around the nozzle tube outlet 52.

[0133] Figure 3 The barrel 30 and the nozzle body 1 of Figure 1 and Figure 2 are illustrated in perspective view, with a gas cap 40 mounted over the barrel and the nozzle body, together forming a spray head assembly 20. The outer surface 75 of the nozzle body 1 at the nozzle tube outlet 52 forms a first portion of the delimiting surface of the atomizing gas passage 33 for guiding pressurized atomizing gas towards the annular atomizing gas outlet 54 which is arranged circumferentially around the nozzle tube outlet 52, so that the atomizing gas exits the atomizing gas passage 33 at the atomizing gas outlet 54 into the external air and atomizes the liquid after the liquid has exited the nozzle tube outlet 52.

[0134] The gas cap 40 includes two gas angles 43a and 43b arranged opposite to each other. Pressurized forming gas exits the gas angles 43a and 43b through two forming gas holes 46 on each of them. The forming gas holes 46 on the gas angles 43a and 43b are located on opposite sides of the spray axis 200, such that the forming gas flowing through the cylinder 30 at a pressure greater than atmospheric pressure is directed to act on opposite sides of the atomized liquid jet exiting the nozzle outlet 52 and entering the outside air in the spray direction 300. The force applied by the forming gas can be used to change the shape of the atomized liquid jet to form a desired spray pattern (e.g., circular, elliptical, etc.).

[0135] Figure 4 yes Figure 3 A longitudinal cross-sectional view of the nozzle assembly 20, which includes, according to Figures 1 to 3 The nozzle body 1 of this disclosure includes a nozzle tube 66 having a nozzle tube wall 71, which in this embodiment has a generally funnel-shaped profile that narrows substantially toward a nozzle tube outlet 52. The liquid to be sprayed flows through a liquid inlet 73, through a cylinder 30, and from a nozzle tube inlet 57 through an elongated nozzle tube passage 58 to a nozzle tube outlet 52. In use, the liquid exits the nozzle tube passage 58 along the spraying axis 200 in the spraying direction 300 and enters the outside air. The length direction of the nozzle tube passage 58 defines an axial direction 220 and a radial direction 210 orthogonal to the axial direction 220. The spraying direction 300 is the axial direction 220.

[0136] The rear part 38 of the cylinder 30 can be attached to the liquid spray gun platform 10 at the cylinder interface 11, such as Figure 1 As shown, the spray gun platform 10 and the nozzle assembly 20 form a complete liquid spray gun.

[0137] Once connected to the nozzle body 1, the air cap 40 is rotationally symmetrical about the spraying axis 200. The air cap has a front wall 60 that forms a circular nozzle orifice defined by a nozzle orifice edge 64. In this embodiment, the tip of the nozzle tube 66 is positioned within the nozzle orifice defined by the nozzle orifice edge 64 of the front wall 60, such that the nozzle tube outlet 52 is almost flush with the front surface 62 of the air cap 40, which is generally oriented towards the spraying direction 300.

[0138] Atomizing gas outlet 54 is formed between the nozzle orifice edge 64 of the front wall 60 of the gas cap 40 and the radial outer surface 75 of the nozzle tube wall 71. Therefore, the atomizing gas outlet 54 has an annular shape and is arranged circumferentially around the nozzle tube outlet 52. The nozzle tube wall 71 is shaped such that a portion of the pressurized atomizing gas exiting the atomizing gas outlet is guided at an angle away from the spray axis 200, and a portion of the liquid exiting the nozzle tube outlet 52 is also guided at an angle away from the spray axis 200.

[0139] Figure 5 is Figure 4 a longitudinal cross-sectional view of a front portion of the nozzle body 1. The nozzle body 1 comprises a tubular nozzle tube 66 which in turn comprises an elongated nozzle tube passage 58 extending longitudinally between a nozzle tube inlet 57 (not visible in Figure 5 the figure) through which liquid enters the nozzle tube 66 in use, and a nozzle tube outlet 52 through which liquid exits the nozzle tube passage 58 into the external air 93 in the spray direction 300 in use. The nozzle tube outlet 52 defines an exact axial position (indicated by the plane 330 of the nozzle tube outlet 52) at which liquid exits the nozzle tube passage 58 into the external air 93. The length direction of the nozzle tube passage 58 defines an axial direction 220 and a radial direction 210 which is orthogonal to the axial direction 220. In Figure 5 embodiments of the application, the nozzle tube 66 is rotationally symmetric about a tube symmetry axis 230, such that both the length direction of the nozzle tube passage 58 and the spray direction 300 are parallel to the tube symmetry axis 230, and the spray axis 200 and the tube symmetry axis 230 are identical. In Figure 5 embodiments of the application, a terminal section 159 of the nozzle tube passage 58 (i.e. an axial section 159 near the nozzle tube outlet 52) has a conical shape, i.e. it has a circular cross-section with an increasing diameter when travelling in the axial direction 220 from the rear to the nozzle tube outlet 52. The conical shape of the nozzle tube outlet 52 provides for a portion of the liquid exiting the nozzle tube outlet 52 to be directed angularly away from the spray axis (200). The orientation of the inner surface 76 of the nozzle tube wall 71 and the conical shape define a wider cross-section in the path of the liquid through the nozzle tube passage 58 when the liquid is drawn out of the nozzle tube outlet 52 by the atomizing gas 110. The wider cross-section at the nozzle tube outlet 52 leads to a radial expansion of the liquid flow. The radial expansion in turn means that some portions of the liquid have trajectories away from the spray axis 200. Thus, the diverging conical shape of the inner surface 76 of the nozzle tube wall 71 causes portions of the liquid to be directed angularly away from the spray axis 200.

[0140] The nozzle tube 66 further comprises a nozzle tube wall 71 comprising a radially outer surface 75 and an opposite radially inner surface 76. The inner surface 76 delimits the nozzle tube passage 58 and is in contact with the liquid when the nozzle body 1 and the spray gun in which it is mounted are in use.

[0141] The spraying direction 300 through the centroid 310 of the cross-section of the nozzle tube outlet 52 defines the spraying axis 200. The cross-section of the nozzle tube outlet 52 has a disc shape. The nozzle tube outlet 52 is arranged around and comprises the spraying axis 200. The nozzle tube outlet comprises the spraying axis 200 because at the centroid 310 the liquid exits the nozzle tube outlet 52. The liquid exits the nozzle tube outlet 52 in a direction centered on the spraying direction 300. Turbulence introduces irregular velocities into the liquid only for a short time after the liquid has exited the nozzle tube outlet 52 and only at a position slightly downstream of the plane 330 of the nozzle tube outlet 52.

[0142] The outer surface 75 of the nozzle tube wall 71 is operable to combine with a surface of a suitable gas cap 40 (not shown) to form an atomizing gas outlet 54 (see Fig. 2) arranged circumferentially around the nozzle tube outlet 52 when the gas cap 40 is directly or indirectly connected with the nozzle body 1, such that the pressurized atomizing gas 110 exits through the atomizing gas outlet 54 and into the external air 93 and atomizes the liquid after the liquid has exited the nozzle tube outlet 52. Figure 6

[0143] The outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52, i.e. in the nozzle tube outlet plane 330, is oriented radially outward to direct at least a portion of the pressurized atomizing gas 110 exiting the atomizing gas outlet 54 angularly away from the spraying axis 200. In Figure 5 In embodiments of the spraying device 10, the outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52 exhibits a "tilted" appearance in a longitudinal cross-sectional view. The tilt angle a (alpha) can be considered as a divergence angle a of the tilted axial section 77, which is measured in the nozzle tube outlet plane 330 relative to the spraying axis 200. The tilt angle a is generally easily visible and measurable in a longitudinal cross-sectional view of the nozzle body 1 taken through the spraying axis 200. The tilted axial section 77 provides a radial velocity component to the pressurized atomizing gas 110 flow, which is angularly away from the spraying axis 200 and angularly away from the liquid jet flowing in the spraying direction 300. Due to the rotational symmetry of the nozzle body 1, Figure 5 The tilted axial section 77 in a cross-sectional view of the spraying device 10 corresponds to a conical axial section 77 of the outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52, wherein the larger diameter end of the conical axial section 77 is located at the axial position of the nozzle tube outlet 52, i.e. in the nozzle tube outlet plane 330, and wherein the smaller diameter end of the conical axial section 77 is located upstream of the nozzle tube outlet 52. "Upstream" refers to a position located in the opposite direction of the spraying direction 300.

[0144] The outer surface 75 of the nozzle tube wall 71 can exhibit a "tilted" appearance as Figure 5 ​The illustrated curvature discontinuity (e.g., step, corner, etc.). For example, it is conceivable that in some alternative embodiments, the outer surface 75 can have a continuous curvature, such as a circular, parabolic, or hyperbolic curvature.

[0145] In Figure 5 embodiments, in a longitudinal cross-sectional view of the Figure 5 embodiments, the angled axial section 77 diverges from the spray axis 200 and the spray direction 300 at an angle a of about 20°. By means of this angled axial section 77, some of the atomizing gas 110 has a velocity vector at the nozzle tube outlet 52 (i.e., in the nozzle tube outlet plane 330) that is directed angularly away from the spray axis 200 and away from the spray direction 300 at an angle of about 20°. This diverging flow of atomizing gas 110 results in a lower pressure of the outside air at the nozzle tube outlet 52 than in conventional nozzle geometries, in which the atomizing gas flows in a direction parallel to or towards the spray axis 200. In Figure 5 embodiments, assuming the same pressure of the supplied pressurized atomizing gas, the lower pressure at the nozzle tube outlet 52 extracts more liquid from the nozzle channel 58 and increases the liquid flow compared to conventional nozzle bodies.

[0146] In Figure 5 embodiments, the angled axial section 77 appears as a straight line in a longitudinal cross-sectional view, which is related to a constant angle a (alpha) of divergence over the axial length of the angled axial section 77. It is conceivable that in alternative embodiments, the angled axial section 77 can be a curved line in a longitudinal cross-sectional view, which is related to an increasing angle a (alpha) of divergence from a rearward upstream portion towards the nozzle tube outlet plane 330 over the axial length of the angled axial section 77. The angle of divergence of the outer surface 75 of the nozzle tube wall 71 measured relative to the spray axis 200 is greater at the nozzle tube outlet 52 (i.e., in the nozzle tube outlet plane 330) than more rearward (i.e., at a more upstream axial position). However, the angle of divergence a is considered to be the angle of divergence in the plane of the nozzle tube outlet 52 (i.e., in the nozzle tube outlet plane 330). The angle of divergence can be determined in a longitudinal cross-sectional view of the nozzle tube wall 71 taken through the spray axis 200. The shape or orientation of the outer surface 75 of the nozzle tube wall 71 directs a portion of the atomizing gas 110 exiting the atomizing gas outlet 54 angularly away from the spray axis 200 also at the nozzle tube outlet plane 330 (rather than at a more rearward or more upstream axial position).

[0147] The radial inner surface 76 of the nozzle tube wall 71 at the nozzle tube outlet 52 (i.e., in the nozzle tube outlet plane 330) is oriented radially outwardly to direct at least a portion of the liquid exiting the nozzle tube outlet 52 angularly away from the spray axis 200. In Figure 5In embodiments of the nozzle body 1, the inner surface 76 of the nozzle tube wall 71 at the nozzle tube outlet 52 forms an opening angle in a longitudinal cross-sectional view. The opening angle β (beta) can be considered as the opening angle β of the diverging axial section 78 of the inner wall 76, which is measured in the nozzle tube outlet plane 330 with respect to the spraying axis 200. The opening angle β is generally easily visible and measurable in a longitudinal cross-sectional view of the nozzle body 1 taken through the spraying axis 200. The diverging axial section 78 provides the liquid flow with a radial velocity component that is angled away from the spraying axis 200. Due to the rotational symmetry of the nozzle body 1, Figure 5 In embodiments of the nozzle body 1, the diverging axial section 78 in cross-sectional view is a conical axial section 78 of the inner surface 76 of the nozzle tube wall 71 at the nozzle tube outlet 52, wherein the larger diameter end of the conical axial section 78 is located at the axial position of the nozzle tube outlet 52 (i.e. in the nozzle tube outlet plane 330), and wherein the smaller diameter end of the conical axial section 78 is located upstream of the nozzle tube outlet 52.

[0148] The opening angle β of the inner surface 76 and the inclination angle a of the outer surface 75 are identical. In Figure 5 In embodiments of the nozzle body 1, the inner surface 76 and the outer surface 75 are thus oriented parallel to each other at the nozzle tube outlet 52. In other embodiments, the opening angle β of the inner surface 76 and the inclination angle a of the outer surface 75 can be different, such that the inner surface 76 and the outer surface 76 can be oriented non-parallel to each other at the nozzle tube outlet 52, but can form an angle between each other.

[0149] In Figure 5 In embodiments of the nozzle body 1, in Figure 5 In a longitudinal cross-sectional view of the nozzle body 1, the diverging axial section 78 diverges from the spraying axis 200 and the spraying direction 300 at an angle β of about 20°. By means of this diverging axial section 78, some portions of the liquid have a velocity vector at the nozzle tube outlet 52 (i.e. in the nozzle tube outlet plane 330) that is directed at an angle of about 20° away from the spraying axis 200 and away from the spraying direction 300. This diverging flow of liquid results in a lower pressure within the liquid at the nozzle tube outlet 52 than in conventional nozzle geometries, in which the liquid exits the nozzle tube outlet 52 in a direction that is parallel to or towards the spraying axis 200. In Figure 6 In embodiments of the nozzle body 1, the lower pressure in the liquid at the nozzle tube outlet 52 in combination with the lower pressure of the external air in front of the nozzle tube outlet 52 extracts more liquid from the nozzle channel 58 and increases the liquid flow compared to conventional nozzle bodies, assuming the same pressure of the supplied pressurized atomizing gas.

[0150] In Figure 4In embodiments, the diverging axial section 78 exhibits a straight line in a longitudinal cross-sectional view, which is related to a constant divergence angle β (beta) over the axial length of the diverging axial section 78. It is conceivable that in alternative embodiments, the diverging axial section 78 can be a curved line in a longitudinal cross-sectional view, which is related to an increasing opening angle β (beta) from a rearward upstream portion towards the nozzle tube outlet plane 330 over the axial length of the diverging axial section 78. In such embodiments, the opening angle of the inner surface 76 of the nozzle tube wall 71 measured relative to the spray axis 200 can be larger at the nozzle tube outlet 52 (i.e. in the nozzle tube outlet plane 330) than more rearward (i.e. at a more upstream axial position). However, the opening angle β is considered to be the opening angle in the plane of the nozzle tube outlet 52 (i.e. in the nozzle tube outlet plane 330). The opening angle β can be determined in a longitudinal cross-sectional view of the nozzle tube wall 71 taken through the spray axis 200. The shape or orientation of the inner surface 76 of the nozzle tube wall 71 directs a portion of the liquid exiting the nozzle tube outlet 52 angularly away from the spray axis 200 also at the nozzle tube outlet plane 330 (rather than at a more rearward or more upstream axial position).

[0151] Figure 5 is Figure 4 and Figure 6 the front of the nozzle body 1 and Figure 7 a further longitudinal cross-sectional view of the front of the gas cap 40.

[0152] The gas cap 40 is rotationally symmetric about the spray axis 200. It is connected in a spatially fixed relationship with the nozzle body 1 via a barrel 30 (not shown) to which both the nozzle body 1 and the gas cap 40 are connected, such that the atomizing gas outlet 54 is radially outwardly bounded by the nozzle orifice edge 64 and radially inwardly bounded by the nozzle tube wall 71 at the nozzle tube outlet 52.

[0153] The gas cap 40 has a front wall 60 which forms a circular nozzle orifice bounded by the circular nozzle orifice edge 64. The front end of the nozzle tube 66 is arranged in the nozzle orifice of the front wall 60 such that the nozzle tube outlet 52 protrudes a small distance in the spray direction 300 from the front surface 62 of the gas cap 40.

[0154] The atomizing gas outlet 54 is formed between the nozzle orifice edge 64 of the front wall 60 and the radially outer surface 75 of the nozzle tube wall 71. Thus, the atomizing gas outlet 54 has an annular shape and is arranged circumferentially around the nozzle tube outlet 52.

[0155] In Figures 4 to 6In embodiments of the nozzle body 1 of the present disclosure, the cylindrical surface 68 extends axially rearward / upstream from the nozzle orifice edge 64. This cylindrical surface 68 directs a portion of the pressurized atomizing gas 110 exiting the atomizing gas outlet 54 in a direction parallel to the spray axis 200. This geometry still allows other portions of the pressurized atomizing gas 110 to be directed angularly away from the spray axis 200 (e.g., by the sloped axial section 77 of the outer surface 75 of the nozzle tube wall 71), thus resulting in a lower pressure of the external air at the nozzle tube outlet 52 than in conventional nozzle geometries in which the atomizing gas flows in a direction parallel to or towards the spray axis 200, and no portion of the pressurized atomizing gas 110 flows angularly away from the spray axis 200.

[0156] Figures 4 to 6 is Figure 7 a longitudinal cross-sectional view of the front of the nozzle body 1 of the present disclosure, which front is connected with an alternative second gas cap 41. The second gas cap 41 is identical to the first gas cap 40 of the present disclosure, except that the nozzle orifice edge 64 of this second gas cap is oriented and shaped to direct a portion of the pressurized atomizing gas 110 exiting the atomizing gas outlet 54 angularly away from the spray axis 200. The nozzle orifice edge 64 is rotationally symmetrical with respect to the spray axis 200, but in the longitudinal cross-sectional view of the present disclosure, the nozzle orifice edge is not parallel to the spray axis 200 and the spray direction 300, but is tilted. Thus, the surface of the nozzle orifice edge 64 forms a conical surface, which is centered on the spray axis 200 and opens in the spray direction 300. Figure 6 Figure 7

[0157] Compared to the first gas cap 40 of the present disclosure, Figure 8A the conical nozzle orifice edge 64 of the second gas cap 41 of the present disclosure helps to direct more of the pressurized atomizing gas 110 angularly away from the spray axis 200. Thereby, this results in an even lower pressure of the external air at the nozzle tube outlet 52 and helps to extract more liquid from the nozzle tube channel 58, while the amount of pressurized atomizing gas 110 remains the same. Figure 8A Figures 8a and 8b show in longitudinal cross-sectional views the pressure distribution in front of the respective nozzle tube outlet 52 when simulated by the inventors of the present disclosure using a computational fluid dynamics (CFD) software package known as FLUENT (available from Ansys Inc., Canonsburg, PA, U.S.A.). The regions of pressure below atmospheric pressure (“low pressure zones”) are located within the low pressure boundary 237 in front of the respective nozzle tube outlet 52.

[0158]

[0159] Figure 8B ​​​The pressure diagram illustrates the pressure distribution obtained in the simulation using a conventional nozzle body 99 combined with an air cap 40, which does not guide any portion of the pressurized atomized gas leaving the atomized gas outlet 54 at an angle away from the spray axis 200. A low-pressure boundary 237 extends downstream from the nozzle outlet 52 and reaches its maximum axial distance from the plane of the nozzle outlet 52 at a radial distance from the spray axis 200, thereby... Figure 8B Two "protrusions" are formed in the cross-sectional view.

[0160] Figure 8A An example is illustrated of the pressure distribution obtained using the nozzle body 1 according to the present disclosure in simulations under other identical conditions, wherein the nozzle body guides a portion of the pressurized atomized gas 110 leaving the atomized gas outlet 54 at an angle away from the spray axis 200 via the shape and orientation of the outer surface 75 of the nozzle wall 71 at an axial position at the nozzle outlet 52, and the nozzle body guides a portion of the liquid leaving the nozzle outlet 52 at an angle away from the spray axis 200.

[0161] Figure 8B and Figure 8A The comparison shows that, under other identical conditions, the nozzle body 1 according to the invention ( Figure 9 The low-pressure zone generated is significantly larger in size than that of a conventional nozzle body (99). Figure 5 The low-pressure zone generated. Compared with the conventional nozzle body 99, the larger low-pressure zone surrounded by the low-pressure boundary 237 in the nozzle body 1 of the present invention helps to extract liquid more effectively from the nozzle tube channel 58 and increase the liquid (e.g., coating) flow rate without increasing the consumption of pressurized atomizing gas.

[0162] When the nozzle body 1 with a high liquid flow rate according to this disclosure is used in a spray gun, the pressure and / or volume of the pressurized atomizing gas can be reduced to obtain a lower liquid flow rate similar to that obtained with a conventional nozzle body 99. This reduction in atomizing gas pressure and / or volume can lead to energy and cost savings. The reduction in atomizing gas pressure also generally results in less high-frequency noise or a lower high-frequency noise volume during spraying operations, which reduces health risks to human spray gun operators. Furthermore, less overspray has been observed when using the nozzle body 1 according to the invention, resulting in increased transfer efficiency.

[0163] Figure 5 This is an xy graph illustrating the liquid flow rate through the nozzle tube outlet of certain nozzle bodies according to this disclosure and the liquid flow rate of certain conventional nozzle bodies. The x-axis shows, for example, the liquid flow rate of the nozzle bodies described above. Figure 9The inclination angle a (alpha) of the outer surface 75 of the nozzle tube wall 71 is explained in the context of FIG. 6, while the y-axis shows the calculated paint flow in g / s for nozzle bodies with different inclination angles. The paint flow in the figure is the simulated paint flow simulated using computational fluid dynamics simulation software. All other parameters were kept constant except for the inclination angle.

[0164] As explained in the context of FIG. 6, the inclined axial section 77 of the outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52 provides the pressurized atomizing gas flow 110 with a radial velocity component that is angled away from the spray axis 200, and the diverging axial section 78 of the inner surface 76 of the nozzle tube wall 71 at the nozzle tube outlet 52 provides the liquid flow with a radial velocity component that is angled away from the spray axis 200. ​

[0165] ​ The graph of FIG. 7 shows that the paint flow of a nozzle body according to the present disclosure, in which the outer surface 75 of the nozzle tube wall 71 has a respective inclination angle of 5° and 10°, is significantly higher than the paint flow of a conventional nozzle body, in which the outer surface of the nozzle tube wall has no slope, i.e. in which the inclination angle is 0°.​

Claims

1. Nozzle body (1) for a liquid spray gun for spraying a liquid, the nozzle body (1) comprising a tubular nozzle tube (66) comprising a) an elongated nozzle tube channel (58) extending longitudinally between a nozzle tube inlet (57) through which the liquid enters the nozzle tube (66) in use and a nozzle tube outlet (52) through which the liquid exits the nozzle tube channel (58) into external air (93) in use in a spray direction (300), wherein the length direction of the nozzle tube channel (58) defines an axial direction (220) and a radial direction (210) orthogonal to the axial direction, b) a nozzle tube wall (71) having a radially outer surface (75) and an opposite radially inner surface (76) bounding the nozzle tube channel (58) and in use in contact with the liquid, wherein the spray direction (300) through the barycenter (310) of a cross section of the nozzle tube outlet (52) defines a spray axis (200) around which the nozzle tube outlet (52) is arranged and comprises, wherein the outer surface (75) of the nozzle tube wall (71) is operable to combine with a surface (64) of a gas cap (40, 41) in direct or indirect connection with the nozzle body (1) to form an atomizing gas outlet (54) circumferentially arranged around the nozzle tube outlet (52) such that pressurized atomizing gas (110) exits through the atomizing gas outlet (54) into external air (93) and atomizes the liquid after the liquid has exited the nozzle tube outlet (52), characterized in that the outer surface (75) of the nozzle tube wall (71) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200), and the radially inner surface (76) of the nozzle tube wall (71) is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet (52) angularly away from the spray axis (200).

2. Nozzle body (1) according to claim 1, wherein the outer surface (75) of the nozzle tube wall (71) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200) at an angle (a) between 0.5° and 45°.

3. Nozzle body (1) according to claim 1 or claim 2, wherein the outer surface (75) of the nozzle tube wall (71) comprises a slanted axial section (77), such as a slanted axial section (77) at the nozzle tube outlet (52), for directing at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200).

4. Nozzle body (1) according to any of the preceding claims, wherein the radially inner surface (76) of the nozzle tube wall (71) is shaped to diverge towards the nozzle tube outlet (52), for example in a linear, parabolic, hyperbolic or exponential function manner.

5. Nozzle body (1) according to any of the preceding claims, wherein at the nozzle tube outlet (52) the inner surface (76) of the nozzle tube wall (71) is oriented parallel to the outer surface (75) of the nozzle tube wall (71).

6. Nozzle body (1) according to any of the preceding claims, wherein the outer surface (75) of the nozzle tube wall (71) comprises a gas guiding portion (77) for directing at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200), and wherein the gas guiding portion (77) has the shape of a radially outer surface of a truncated cone.

7. Nozzle body (1) according to any of the preceding claims, wherein the outer surface (75) and the inner surface (76) of the nozzle tube wall (71) at the nozzle tube outlet (52) are circular in a cross-section taken in a plane orthogonal to the spray axis (200).

8. Nozzle body (1) according to claim 6, wherein the outer surface (75) of the nozzle tube wall (71) at the nozzle tube outlet (52) extends over a full 360° angle in the circumferential direction.

9. Nozzle body (1) according to any of the preceding claims, wherein the outer surface (75) of the nozzle tube wall (71) at the nozzle tube outlet (52) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200), and / or wherein the radially inner surface (76) of the nozzle tube wall (71) at the nozzle tube outlet (52) is oriented or shaped to direct at least a portion of the liquid exiting the nozzle tube outlet (52) angularly away from the spray axis (200).

10. Nozzle assembly (20) comprising a nozzle body (1) according to any of the preceding claims, and a gas cap (40) connected in a fixed spatial relationship with the nozzle body (1), wherein the gas cap (40) comprises i) a front wall (60) facing generally in the spray direction (300) and comprising a nozzle aperture delimited by a nozzle aperture edge (64), and optionally ii) a gas cap wall (80) extending from the front wall (60) and comprising a gas cap aperture (84) delimited by a gas cap aperture edge (86), wherein the gas cap aperture (84) is arranged in a fixed spatial relationship with the nozzle aperture (62) of the front wall (60) of the nozzle body (1). ​ ii) two gas horns (43a, 43b) arranged opposite to each other with respect to the spray axis (200), each gas horn comprising a shaping gas orifice (46) for directing shaping gas to act on atomized liquid exiting the nozzle tube outlet (52) into the external air in the spray direction (300); and wherein the nozzle tube (66) is arranged in or projects outwardly through the nozzle aperture such that the atomizing gas outlet (54) is formed between the nozzle aperture edge (64) and the nozzle tube wall (71).

11. The nozzle assembly (20) of claim 10, wherein the nozzle aperture edge (64) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110) exiting the atomizing gas outlet (54) angularly away from the spray axis (200).

12. The nozzle assembly (20) of any one of claims 10 to 11, wherein the nozzle tube outlet (52), the nozzle tube wall (71), the nozzle aperture edge (64), and the atomizing gas outlet (54) each have a rotational symmetric shape and are arranged concentrically with respect to the spray axis (200).

13. The nozzle assembly (20) of any one of claims 10 to 12, further comprising a cartridge (30) having a liquid port connector (74) for directly or indirectly connecting a liquid reservoir to the cartridge (30), wherein the gas cap (40) is connected with the cartridge (30) and the nozzle body (1) is connected with the cartridge (30) such that the gas cap (40) is connected in a fixed spatial relationship with the nozzle body (1).

14. Liquid spray gun for spraying a liquid, the liquid spray gun comprising a nozzle body (1) according to any one of claims 1 to 9 or a nozzle assembly (20) according to any one of claims 10 to 13.

15. Non-transitory machine readable medium having stored thereon data representing a three-dimensional model of a nozzle body (1) according to any one of claims 1 to 9 or a three-dimensional model of a nozzle assembly (20) according to any one of claims 10 to 13, the data being formatted to be accessed by one or more digital processors interfacing with a 3D printer, wherein the one or more digital processors are operable to cause the 3D printer to manufacture a nozzle body (1) according to any one of claims 1 to 9 or a nozzle assembly (20) according to any one of claims 10 to 13.

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