Diaphragm for a device for applying a coating product and associated application device

Abstract

The invention relates to a diaphragm (54) for an application device for coating a product, the diaphragm (54) comprising a duct (62) defining a passage for circulation of the product, the duct (62) extending between an inlet end (64) and an outlet end (66) along a central axis (B-B') and having a cylindrical symmetry around the central axis (B-B'). The duct (62) comprises in succession an upstream portion (70) and a downstream portion (72). The duct (62) comprises a throttling portion (74) arranged between the upstream and downstream portions (70, 72) and having a cross section that is constricted with respect to the cross sections of the upstream and downstream portions. The upstream and downstream portions each have a general shape that diverges, preferably convexly diverges, from the throttling portion (74) towards the respective end (64, 66) of the duct (62).

Description

Technical Field

[0001] The present invention relates to a diaphragm for an application device (particularly a spray gun for coating products), a spray nozzle including such a diaphragm, and an application device including such a diaphragm. Background Technology

[0002] Application devices for coating products, such as spray guns, are known. These devices are designed to ensure that the coating product is broken into fine droplets, thus covering a large surface with a small amount of product. For this purpose, the coating product is supplied under pressure from a source and delivered to the spray nozzle.

[0003] Several solutions exist for achieving this type of spraying.

[0004] First, pneumatic spraying can be mentioned. In this method, the coating product is supplied from a source at a very low overpressure relative to atmospheric pressure, typically between 0.5 bar and 1.5 bar. Compressed air is blown out at the nozzle outlet, and primarily this compressed air atomizes the liquid film ejected from the nozzle. The advantage of this method is that it provides very high surface finish quality. It is also relatively inexpensive. However, its disadvantage is low delivery rate, with a large amount of coating product dispersing into the environment without reaching the surface to be coated.

[0005] Another approach is airless spraying. In this approach, the coating product is supplied from a source at very high pressure, typically between 160 and 300 bar. The product then breaks down only due to the narrowness of the spray nozzle. No air is involved. The advantage of this approach is its excellent transfer rate. However, its disadvantages include the need for pumping equipment capable of supplying the coating product at very high pressures and the high cost of energy consumption.

[0006] The final approach is hybrid spraying. In this technique, the coating is supplied from a source under high pressure, typically between 50 and 150 bar. Similar to airless spraying, the narrow nozzle orifice causes product breakage. However, this method is not optimal given the relatively low pressure at which the coating is supplied. To improve atomization, compressed air is blown out of the nozzle, as in pneumatic spraying. This compressed air is also blown towards the jet tip to cause the sprayed paint to fold back and prevent the formation of concentrated paint sections known as angles under these pressures. This approach allows for surface finish quality essentially the same as airless spraying, with good transfer rates, while being more economical because the coating is supplied at lower pressure. However, its disadvantage compared to pneumatic spraying is that the cost remains relatively high. Summary of the Invention

[0007] The purpose of this invention is to reduce the pressure of having to supply coating products while maintaining satisfactory transfer rates and surface treatment quality.

[0008] Therefore, the present invention relates to a diaphragm for an application device for coating a product, the diaphragm comprising a conduit defining a passage for product flow, the conduit extending along a central axis between an inlet end and an outlet end and having cylindrical symmetry about the central axis, the conduit comprising an upstream portion and a downstream portion sequentially between the inlet end and the outlet end, the conduit comprising a throttling portion disposed between the upstream portion and the downstream portion and having a cross-section narrowed relative to the cross-sections of the upstream portion and the downstream portion, the upstream portion and the downstream portion each having an overall shape that gradually widens from the throttling portion toward the respective end of the conduit, preferably convexly widening.

[0009] The shape of the diaphragm according to the invention thus allows the product to be progressively accelerated by progressively reducing the passage cross-section in the upstream portion, allowing the product to flow at high speed in a throttling portion with a constant cross-section, and finally the product speed to be progressively reduced by progressively increasing the passage cross-section in the downstream portion.

[0010] Therefore, compared to conventional application devices, products can be sprayed at lower pressure while maintaining good coating quality.

[0011] The reduction in required pressure leads to a reduction in required energy, and it is possible to use pressurization equipment that can achieve lower pressure, thus providing users with double savings in terms of energy and equipment.

[0012] Furthermore, this invention helps reduce the volume of the area that may be occupied by the product under pressure after spraying stops. Therefore, the diaphragm allows for a reduction in the volume between the needle and nozzle exit of the application device, also known as the "dead" volume.

[0013] In addition, the constraint formed by the diaphragm helps to retain the liquid in this "dead" volume, so that once spraying has stopped, the liquid will not flow and will not leave the nozzle.

[0014] The rounded shape of each part helps to limit pressure loss and turbulence, thus enabling a product flow that is as laminar as possible.

[0015] Therefore, there is less turbulence in the spraying process, which improves the transmission rate of the sprayed product and requires less air extraction in the spraying chamber.

[0016] Therefore, the diaphragm according to the invention makes it possible to reduce the pressure required to supply the coated product while maintaining a satisfactory transfer rate and surface treatment quality.

[0017] According to other advantageous aspects of the invention, the diaphragm may include one or more of the following features, presented individually or in any technically possible combination:

[0018] - The throttling section has a cylindrical shape with a constant cross-section;

[0019] - At least one of the upstream and downstream portions is tangent to the throttling portion;

[0020] - The upstream and downstream portions each have a corresponding radius of curvature, which may be constant or variable;

[0021] - The radius of curvature of the upstream section is different from that of the downstream section;

[0022] - The radius of curvature of the downstream section is strictly larger than that of the upstream section;

[0023] - The upstream section includes a truncated conical inlet section;

[0024] - The upstream and downstream portions each have a length measured along the central axis, such that the length of the upstream portion is between 50% and 100% of the length of the downstream portion, preferably between 70% and 90%.

[0025] - The diaphragm also includes a base at which the conduit opens at the inlet end of the conduit;

[0026] - The base includes at least one notch or protrusion that characterizes the shape and / or length of the pipe.

[0027] The present invention also relates to a nozzle for an application device for coating a product, the nozzle comprising at least one diaphragm of the type described above.

[0028] According to other advantageous aspects of the invention, the nozzle may also have one or more of the following features, either individually or in any technically possible combination:

[0029] - The nozzle includes a tubular body oriented in an axial direction and internally defining a through passage leading to a spray orifice suitable for spraying a product. The nozzle also includes a spraying member defining a spray orifice and including, from upstream to downstream: a cavity with a cross-section decreasing downstream, followed by a channel for fluidly connecting the cavity to the spray orifice, and a diaphragm at least partially housed in the through passage of the nozzle.

[0030] - The diaphragm is preferably removably, at least partially, housed within the cavity of the spraying component;

[0031] - The diaphragm is preferably removably housed upstream of the spraying component.

[0032] The present invention also relates to an application device for coating products, such as a gun, which includes a nozzle and the application device further includes at least one diaphragm of the type described above.

[0033] According to other advantageous aspects of the invention, the device may also have one or more of the following features, presented individually or in any technically possible combination:

[0034] - The nozzle includes a tubular body oriented in an axial direction and internally defining a through passage leading to a spray orifice suitable for spraying a product. The nozzle also includes a spraying member defining a spray orifice and including, from upstream to downstream: a cavity with a cross-section decreasing downstream, followed by a channel for fluidly connecting the cavity to the spray orifice, and a diaphragm at least partially housed in the through passage of the nozzle.

[0035] - The diaphragm is preferably removably, at least partially, housed within the cavity of the spraying component;

[0036] -The diaphragm is preferably removably housed upstream of the spraying component;

[0037] - The device includes a seat retainer adapted to receive the nozzle in an abutting manner, the seat retainer defining a diaphragm. Attached Figure Description

[0038] The invention will be more clearly presented by reading the following description, given only as a non-limiting example and with reference to the accompanying drawings, wherein:

[0039] [ Figure 1 ] Figure 1 This is an exploded perspective view taken from the front three-quarters angle of the application device for coating a product according to the first embodiment of the present invention;

[0040] [ Figure 2 ] Figure 2 It includes the diaphragm according to the first embodiment of the present invention. Figure 1 A longitudinal sectional view of the spray nozzle of the device shown;

[0041] [ Figure 3 ] Figure 3 yes Figure 2 The diaphragm shown is a cross-sectional perspective view.

[0042] [ Figure 4 ] Figure 4 yes Figure 2 An enlarged view of the diaphragm shown;

[0043] [ Figure 5 ] Figure 5 It includes a diaphragm with a variation according to the first embodiment of the present invention. Figure 1 A longitudinal sectional view of the spray head of the device shown;

[0044] [ Figure 6 ] Figure 6 According to the second embodiment Figure 1Partial longitudinal sectional view of the application device shown;

[0045] [ Figure 7 ] Figure 7 It is a variation of the second embodiment. Figure 1 A partial longitudinal sectional view of the application device shown. Detailed Implementation

[0046] exist Figure 1 The image shows an application device 8 for coating a product according to a first embodiment.

[0047] The application device 8 is designed to apply a coating product to the surface to be coated. The coating product is preferably a fluid, such as a liquid or powder material comprising one or more components. The coating product can be a paint, primer, varnish, etc.

[0048] In the following text, the directional terms “upstream” and “downstream” should be understood with reference to the flow direction of the coating product in the application device 8, from upstream to downstream.

[0049] exist Figure 1 In the example shown, the application device 8 is a spray gun, specifically a manual spray gun. As a variation, the spray gun is an automatic spray gun.

[0050] The application device 8 includes a body 10, a handle 11, and an actuation trigger 12 hinged to the body 10. The application device 8 also includes a spray head 14 mounted on the body 10.

[0051] The main body 10 has an outlet orifice 16 for coating products.

[0052] The spray head 14 is centered on the spray axis X-X' of the application device 8.

[0053] The spray head 14 includes an annular ring 20 having a central orifice 22 and a spray nozzle 24 housed in the central orifice 22.

[0054] The annular ring 20 is centered on the axis X-X'. The ring 20 includes a body 26 defining a central aperture 22 and a skirt 28 rotatably mounted relative to the body 26 about the axis X-X'.

[0055] like Figure 1 As can be seen, the main body 26 has a downstream surface 30 that is oriented away from the main body 10 and an upstream surface (not visible) that faces the main body 10.

[0056] The spray nozzle 24 is coaxially arranged inside the head 14.

[0057] The spray head 14 and spray nozzle 24 are configured to be mounted on the seat retainer ( Figure 1(Not shown in the image) The seat holder itself is mounted on the body 10 of the application device 8.

[0058] refer to Figure 2 The spray nozzle 24 includes a tubular body 34 oriented along an axial direction A-A', which coincides with the spray axis X-X' when the spray nozzle 24 is installed in the head 14. The spray nozzle 24 also includes a spraying member 36 disposed within the body 34.

[0059] Specifically, the body 34 of the spray nozzle 24 is a cylinder that rotates about the axis A-A'.

[0060] The body 34 of the spray nozzle 24 has an upstream end 37 oriented toward the body 10 of the application device 8 and a downstream end 38 away from the body 10.

[0061] The body 34 internally defines a through conduit 40 that defines a passage for the flow of the coated product through the spray nozzle 24. The through conduit 40 leads to the outside of the body 34, opening at an upstream end 37 to a wide connecting orifice 41 and at a downstream end 38 to a spray nozzle 42 suitable for spraying the product.

[0062] The sprayed component 36 is partially inserted into the through pipe 40.

[0063] The spraying component 36 has an upstream surface 43 housed in the through pipe 40 and a downstream surface 44 opposite to the upstream surface 43 and arranged outside the body 34.

[0064] The upstream face 43 is basically flat and is arranged basically transversely to axis A-A'.

[0065] The downstream face 44 is typically dome-shaped with the axis A-A' as its center, and the periphery of the downstream face is flush with the downstream end 38 of the through pipe 40.

[0066] The spraying component 36 defines a spraying orifice 42 at its downstream surface 44.

[0067] From upstream to downstream, the spraying component 36 also includes: a cavity 46 with a cross-section decreasing downstream, followed by a channel 48 with a substantially constant cross-section that fluidly connects the cavity 46 to the spraying orifice 42.

[0068] The cavity 46 opens in the upstream face 43, which defines an annular shoulder 50 oriented upstream around the cavity 46.

[0069] exist Figure 2 In the example shown, cavity 46 has a substantially bell-shaped form.

[0070] Channel 48 leads to the opening that forms the spray nozzle 42.

[0071] The application device 8 also includes at least one diaphragm 54.

[0072] According to the first embodiment, the diaphragm 54 is in Figures 2 to 4 As shown in the image.

[0073] Preferably, the diaphragm 54 is formed as a single piece.

[0074] like Figure 2 As can be seen, the diaphragm 54 according to the first embodiment is housed in the through-channel 40 of the spray nozzle 24. In particular, the diaphragm 54 is preferably removably and partially housed in the cavity 46 of the spray member 36.

[0075] refer to Figure 3 and Figure 4 The diaphragm 54 includes a base 56 and an insertion body 58 that protrudes axially from the base 56 along a central axis B-B', which coincides with the longitudinal axis A-A' when the diaphragm 54 is installed in the spray nozzle 24.

[0076] The base 56 is housed within the through-duct 40 of the spray nozzle 24 and outside the cavity 46 of the spraying component 36. Advantageously, as Figure 2 As can be seen, the base 56 abuts against the annular shoulder 50 at its downstream surface 56B. The base 56 also defines an upstream surface 56A opposite to the downstream surface 56B.

[0077] Preferably, as in Figure 3 As can be seen in the cross-sectional view shown, the base 56 has at least one, in particular two, flat portions 59 to allow the diaphragm 54 to be gripped and removed from the spray nozzle 24.

[0078] Preferably, such as Figure 2 As can be seen, the insertion body 58 is completely received within the cavity 46. The insertion body 58 preferably has a shape substantially complementary to the shape of the cavity 46, such that when the insertion body 58 is completely received within the cavity 46, a free space 60 is defined between the insertion body 58 and the inner wall of the cavity 46, the free space 60 having an internal volume smaller than the volume of the cavity 46. This reduces the product stagnation volume.

[0079] The insertion body 58 includes a conduit 62 that defines a passage for product flow. The conduit 62 extends along a central axis B-B' between an inlet end 64 and an outlet end 66 (forming the free end of the insertion body 58).

[0080] The conduit 62 opens at the inlet end 64 of the conduit at the base 56. The conduit 62 is defined by the inner surface 68 of the insertion body 58.

[0081] Preferably, the pipe 62 has a height h measured along the central axis B-B' between the inlet end 64 and the outlet end 66, which is between 3 mm and 12 mm, more preferably between 3.5 mm and 6 mm.

[0082] The insert body 58 advantageously possesses cylindrical symmetry about the central axis B-B'.

[0083] The cross-section of pipe 62 is defined as the section of pipe 62 in a transverse plane orthogonal to the central axis B-B'.

[0084] exist Figures 2 to 4 In the illustrated embodiment, pipe 62 has a generally circular cross-section.

[0085] like Figure 3 and Figure 4 As shown, the pipe 62 includes an upstream portion 70 and a downstream portion 72 sequentially between the inlet end 64 and the outlet end 66. The pipe 62 also includes a throttling section 74 disposed between the upstream portion 70 and the downstream portion 72.

[0086] From upstream to downstream, pipeline 62 therefore includes an upstream section 70, a throttling section 74, and a downstream section 72.

[0087] The throttling portion 74 has a cross-section that is narrower than the cross-sections of the upstream portion 70 and the downstream portion 72.

[0088] Therefore, pipe 62 has an inner diameter that varies between inlet end 64 and outlet end 66. Thus, the inner diameter gradually decreases from inlet end 64 to throttling section 74, and then gradually increases from throttling section 74 to outlet end 66.

[0089] Therefore, the upstream portion 70 defines a converging tube, with the diameter of the inlet end 64 being larger than the diameter of the throttling portion 74. The downstream portion 72 defines a diverging tube, with the diameter of the outlet end 66 being larger than the diameter of the throttling portion 74. The converging and diverging tubes are coaxial.

[0090] The ratio of the cross-sectional diameter of the upstream portion 70 at the throttling portion 74 to the cross-sectional diameter of the upstream portion 70 at the inlet end 64 is preferably between 0.05 and 0.35, and more preferably between 0.07 and 0.22.

[0091] For example, the upstream portion 70 has a diameter between 2.0 mm and 6.0 mm, preferably between 2.5 mm and 4.0 mm, at the inlet end 64, and a diameter between 0.15 mm and 1.0 mm, preferably between 0.15 mm and 0.7 mm, at the throttling portion 74.

[0092] The ratio of the cross-sectional diameter of the downstream portion 72 at the throttling portion 74 to the cross-sectional diameter of the downstream portion 72 at the outlet end 66 is preferably between 0.1 and 0.40.

[0093] For example, the diameter of the downstream portion 72 at the outlet end 66 is between 0.5 mm and 7.0 mm, and the diameter at the throttling portion 74 is between 0.15 mm and 1.0 mm, preferably between 0.15 mm and 0.7 mm.

[0094] According to a particular embodiment (not shown), the upstream portion 70 and the downstream portion 72 are symmetrical about each other with respect to the intermediate plane, and the pipe 62 has a substantially catenary shape.

[0095] Preferably, such as Figures 2 to 4 It is evident that the upstream portion 70 and the downstream portion 72 are asymmetrical.

[0096] The upstream portion 70 and the downstream portion 72 each have corresponding lengths L70 and L72 measured along the central axis B-B'. Preferably, the length L70 of the upstream portion 70 is less than the length L72 of the downstream portion 72.

[0097] Preferably, the length L70 of the upstream portion 70 is between 50% and 100% of the length L72 of the downstream portion 72, and more preferably between 70% and 90%.

[0098] Typically, the length L70 of the upstream portion 70 is between 1.4 mm and 6.0 mm, and the length L72 of the downstream portion 73 is between 1.6 mm and 7.0 mm.

[0099] like Figure 3 and Figure 4 It can be seen that the upstream portion 70 and the downstream portion 72 each have an overall shape that gradually expands from the throttling portion 74 toward the corresponding ends 64 and 66 of the pipe 62.

[0100] Advantageously, such as in Figure 3 and Figure 4 As can be seen in more detail, the upstream portion 70 and the downstream portion 72 each have an overall shape that gradually expands convexly from the throttling portion 74 to the corresponding ends 64, 66 of the pipe 62.

[0101] Therefore, the upstream portion 70 advantageously has a rounded shape that gradually widens from the throttling portion 74 toward the inlet end 64.

[0102] Preferably, such as Figure 4 As can be seen, the upstream portion 70 includes a truncated conical inlet portion 76, which opens at the upstream face 56A of the base 56. The inlet portion 76 allows for an avoidance of an overly abrupt reduction in the cross-section of the pipe 62, while having an inlet end 64 of a suitable diameter.

[0103] Advantageously, the inlet portion 76 is tangent to the rest of the upstream portion 70, and the inner surface 68 of the upstream portion 70 has no edge.

[0104] Preferably, the inlet portion 76 defines a convergence angle α between 90° and 150°, more preferably between 120° and 150°.

[0105] Therefore, the upstream section 70 allows for uniform acceleration of the product over a short distance by uniformly reducing the cross-sectional area of ​​the passage. Starting with a diameter similar to that of the product supply pipeline, this reduction advantageously occurs without abrupt changes.

[0106] The downstream portion 72 advantageously has a rounded shape that gradually widens from the throttling portion 74 toward the outlet end 66.

[0107] The circular shape of the downstream section 72 allows it to benefit from the Coanda effect. The product flow is therefore as wide and undisturbed as possible, which limits cavitation effects or product stagnation. The widening outlet thus limits turbulence, pressure loss, and microbubbling effects of the ejected product.

[0108] Therefore, the upstream portion 70 and the downstream portion 72 each have a funnel shape. The rounded shape of the upstream portion 70 and the downstream portion 72 allows for the limitation of pressure loss and turbulence, thereby achieving laminar flow.

[0109] Pipe 62 has a double funnel shape.

[0110] The diaphragm 54 reduces the product pressure required for spraying by first reducing and then expanding the cross-section of the pipe 62 before the channel 48 of the spraying component 36, thus benefiting from a double constraint effect.

[0111] In addition, the double funnel shape facilitates cleaning of pipe 62 and thus removes any impurities that are harmful to spraying.

[0112] The upstream portion 70 and the downstream portion 72 each have their respective radii of curvature. Any possible truncated conical inlet portion 76 is not considered here.

[0113] exist Figures 2 to 4 In the illustrated embodiment, the radii of curvature of the upstream portion 70 and the downstream portion 72 are constant. Therefore, the curvature of the inner surface 68 at the upstream portion 70 is a simple curve with a constant radius, and the curvature of the inner surface 68 at the downstream portion 72 is also a simple curve with a constant radius.

[0114] In a variant not shown, at least one radius of curvature is variable. In this case, at least one of the upstream portion 70 and the downstream portion 72 includes a series of portions with variable radii of curvature, each portion being tangent to the preceding portion and / or the following portion.

[0115] Advantageously, the radius of curvature of the upstream portion 70 is different from that of the downstream portion 72.

[0116] Preferably, such as Figure 4 It is evident that the radius of curvature of the downstream portion 72 is significantly larger than that of the upstream portion 70.

[0117] This allows the deceleration of the product flow to be more gradual than its acceleration.

[0118] For example, the radius of curvature of the upstream portion 70 is between 0.5 mm and 4.0 mm, preferably between 1.2 mm and 2.0 mm.

[0119] For example, the radius of curvature R72 of the downstream portion 72 is between 2.0 mm and 6.0 mm.

[0120] Preferably, at least one of the upstream portion 70 and the downstream portion 72 is tangent to the throttling portion 74. Even more preferably, both the upstream portion 70 and the downstream portion 72 are tangent to the throttling portion 74, such that there is no discontinuity on the inner surface 68 of the pipe 62 between the inlet end 64 and the outlet end 66. This means that there are no edges on the inner surface 68 of the pipe 62 between different portions.

[0121] The throttling section 74 defines the narrowing portion of the pipe 62.

[0122] This constrained area is where product flow is fastest.

[0123] like Figures 2 to 4 It can be seen that the throttling portion 74 preferably has a cylindrical shape with a constant cross-section centered on the central axis B-B'.

[0124] The length of the throttling section 74 is selected to reduce microbubbling in the sprayed product while limiting pressure loss.

[0125] Preferably, the throttling portion 74 has a length L74 between 0.30 mm and 2.0 mm, measured along the central axis BB.

[0126] Preferably, the diameter of the throttling portion 74 is between 0.15 mm and 1.0 mm, and more preferably between 0.15 mm and 0.7 mm.

[0127] The reduced cross-section at the upstream portion 70, and optionally at the inlet portion 76, allows for gradual acceleration of the product. At the throttling portion 74, the constant cross-section of the pipe 62 allows for high-speed movement of the product, while the increased cross-section at the downstream portion 72 allows for deceleration of the product.

[0128] This helps reduce the pressure required for spraying, especially by reducing the viscosity of the product (particularly coatings) by influencing the rheofluidifying property.

[0129] The reduction in cross-section at the 74 throttling points not only allows for rapid product movement but also enables localized reduction in static pressure. This contributes to the overall effect of reduced spray pressure, particularly by influencing the thixotropic properties of the product (especially the coating) to lower its viscosity.

[0130] Preferably, the diaphragm 54 has at least one notch 78 or protrusion, for example at its base 56, that characterizes the shape and / or length of the conduit 62. For example, the shape and / or location of the notch 78 or protrusion depends on the shape and / or length of the conduit 62. This allows for rapid identification of the diaphragm without the need for measurement.

[0131] Preferably, the diaphragm 54 is made of a metallic material. For example, the diaphragm 54 is made of a metal oxide, particularly zirconium oxide (ZrO2) (also known as zirconium oxide ceramic).

[0132] like Figure 2 As can be seen, the spray nozzle 24 advantageously includes a sealing gasket 80, such as an O-ring, arranged in the through pipe 40. The sealing gasket 80 rests against the upstream surface 56A.

[0133] The operation of the application device 8 according to the first embodiment will now be described.

[0134] The user actuates the trigger 12, thereby supplying products to the spray head 14.

[0135] The coating product, arriving under pressure, enters the through-duct 40 of the spray nozzle 24, and then passes through the duct 62 of the diaphragm 54—in sequence through the upstream section 70, the throttling section 74, and the downstream section 72.

[0136] The reduced cross-section at the upstream section 70 allows the sprayed product to accelerate, then flows rapidly in the throttling section 74, and then decelerates in the downstream section 72.

[0137] Then, the product leaves the pipe 62 and reaches the free space 60 in the cavity 46, then enters the channel 48 and leaves the spray nozzle 24 through the spray orifice 42.

[0138] The coating product is then dispersed into droplets in the space at the outlet of the spray nozzle 24. Despite the relatively low supply pressure of the coating product, excellent coating product dispersibility was achieved, at least similar to that observed with conventional supply pressures.

[0139] The application device 8 according to the invention thus makes it possible to obtain the same or even better surface treatment quality and transfer rate as usually encountered, however, this is achieved with reduced coating product supply pressure.

[0140] Furthermore, the compactness of the diaphragm 54 and its insertion into the spraying member 36 minimize dead volume and thus prevent unwanted flow when the trigger 12 is released, especially when using products with high flowability.

[0141] Figure 5 A spray head 14 including a modified spray nozzle 24 according to the first embodiment is shown. Hereinafter, for the sake of brevity, only the differences from the first embodiment will be mentioned. Furthermore, elements similar to or identical to those of the first embodiment described retain their reference numerals, while other elements are given different reference numerals.

[0142] According to this variation, the diaphragm 54 is preferably removably arranged upstream of the spraying member 36. Therefore, the diaphragm 54 is arranged outside the cavity 46.

[0143] The diaphragm 54 preferably has a shape that is substantially complementary to the internal shape of the through-channel 40 of the spray nozzle 24.

[0144] The diaphragm 54 includes an upstream surface 100 and an opposing downstream surface 102, the downstream surface 102 advantageously abutting against the spraying member 36, particularly against the shoulder 50.

[0145] The conduit 62 of the diaphragm 54 leads into the cavity 46 at its outlet end 66.

[0146] The diaphragm 54 can have a body shape that is not complementary to the shape of the cavity 46 of the spraying component 36. Such a diaphragm 54 can therefore be easily adapted to different spraying components 36.

[0147] Figure 6 and Figure 7 An application device 8 according to a second embodiment is shown. Hereinafter, for the sake of brevity, only the differences from the first embodiment will be mentioned. Furthermore, elements similar to or identical to those in the first embodiment retain their reference numerals, while other elements are given different reference numerals.

[0148] In this second embodiment, the diaphragm 54 is preferably removably and at least partially arranged outside the through-duct 40 of the spray nozzle 24, upstream of the spraying member 36.

[0149] The application device 8 includes a seat holder 120, which is mounted on the body 10 of the application device 8 and is designed to receive the seat 122 of the spray nozzle 24 in an abutting manner.

[0150] According to a first variation of the second embodiment, such as Figure 6 As shown, the seat retainer 120 directly defines the diaphragm 54.

[0151] Therefore, the seat retainer 120 has a downstream end 124 that defines a double funnel-shaped conduit 62.

[0152] When the spray nozzle 24 is mounted on the body 20 of the application device 8, the downstream end 124 is partially received in the through pipe 40.

[0153] Preferably, the sealing gasket 126 (in this case, an O-ring) is held between the downstream end 124 of the seat retainer 120 and the spraying member 36.

[0154] According to a second variation of this second embodiment, such as Figure 7 As shown, the diaphragm 54 is formed by an intermediate component 140, which is itself designed to be mounted on the seat retainer. Figure 7 (Not visible in the middle) and thus arranged between the seat holder and the spray nozzle 24.

[0155] Therefore, the intermediate component 140 defines the double funnel-shaped pipe 62.

[0156] The intermediate component 140 is advantageously removable.

[0157] The intermediate component 140 forming the diaphragm is partially received in the through conduit 40 and preferably abuts against a gasket 142, which is then clamped against the spraying component 36.

[0158] According to another embodiment (not shown), the application device 8 includes a plurality of diaphragms 54 as defined above. For example, the application device 8 includes a first diaphragm 54 in the form of an insert received in the cavity 46, and a second diaphragm formed by the downstream end 124 of the seat holder 120.

[0159] According to a variant not shown, the throttling portion 74 forms a narrowing at the plane corresponding to the junction between the upstream portion 70 and the downstream portion 72.

[0160] According to a variant not shown, the upstream portion 70 and / or downstream portion 72 gradually expand linearly from the throttling portion 74 toward the corresponding ends 64, 66 of the pipe 62. Thus, the radius of curvature of the upstream and / or downstream portions is infinite.

[0161] The above-described variations and embodiments can be combined to produce new embodiments of the present invention.

Claims

1. A diaphragm (54) for an application device (8) for coating a product, the diaphragm (54) comprising a conduit (62) defining a passage for product flow, the conduit (62) extending along a central axis (B-B') between an inlet end (64) and an outlet end (66) and having cylindrical symmetry about the central axis (B-B'). The pipe (62) includes an upstream portion (70) and a downstream portion (72) between the inlet end (64) and the outlet end (66). The pipe (62) includes a throttling section (74) arranged between the upstream section (70) and the downstream section (72) and having a cross-section that is narrower than the cross-sections of the upstream section (70) and the downstream section (72). The upstream portion (70) and the downstream portion (72) each have an overall shape that gradually expands, preferably convexly, from the throttling portion (74) toward the respective ends (64, 66) of the pipe (62).

2. The diaphragm (54) according to claim 1, characterized in that, The throttling section (74) has a cylindrical shape with a constant cross-section.

3. The diaphragm (54) according to claim 1 or 2, characterized in that, At least one of the upstream portion (70) and the downstream portion (72) is tangent to the throttling portion (74).

4. The diaphragm (54) according to claim 1 or 2, characterized in that, The upstream portion (70) and the downstream portion (72) each have a corresponding radius of curvature, which is constant or variable.

5. The diaphragm (54) according to claim 4, characterized in that, The radius of curvature of the upstream portion (70) is different from the radius of curvature of the downstream portion (72).

6. The diaphragm (54) according to claim 5, characterized in that, The radius of curvature of the downstream portion (72) is strictly greater than the radius of curvature of the upstream portion (70).

7. The diaphragm (54) according to claim 1 or 2, characterized in that, The upstream portion (70) includes a truncated conical inlet portion (76).

8. The diaphragm (54) according to claim 1 or 2, characterized in that, The upstream portion (70) and the downstream portion (72) each have lengths (L70, L72) measured along the central axis (B-B') such that the length of the upstream portion (70) is between 50% and 100% of the length of the downstream portion (72), preferably between 70% and 90%.

9. The diaphragm (54) according to claim 1 or 2, characterized in that, The diaphragm also includes a base (56) at which the conduit (62) opens at the inlet end (64) of the conduit.

10. The diaphragm (54) according to claim 9, characterized in that, The base (56) includes at least one notch (78) or protrusion that characterizes the shape and / or length of the pipe (62).

11. A spray nozzle (24) for an application device (8) for coating a product, the application device being such as a spray gun, the spray nozzle (24) comprising at least one diaphragm (54) according to claim 1 or 2.

12. The spray nozzle (24) according to claim 11, characterized in that, The spray nozzle includes a tubular body (34) oriented along an axial direction (A-A') and internally defining a through conduit (40) leading to a spray orifice (42) suitable for spraying the coated product. The spray nozzle (24) also includes a spraying member (36) that defines the spraying orifice (42) and includes, from upstream to downstream: a cavity (46) with a cross-section decreasing downstream, followed by a channel (48) that fluidly connects the cavity (46) to the spraying orifice (42). The diaphragm (54) is at least partially housed in the through-duct (40) of the spray nozzle (24).

13. The spray nozzle (24) according to claim 12, characterized in that, The diaphragm (54) is preferably removably, at least partially, housed in the cavity (46) of the spraying member (36).

14. The spray nozzle (24) according to claim 12, characterized in that, The diaphragm (54) is preferably removably housed upstream of the spraying member (36).

15. An application device (8) for coating a product, such as a spray gun, the application device including a spray nozzle (24), the application device (8) further including at least one diaphragm (54) according to claim 1 or 2.

16. The application device (8) according to claim 15, characterized in that, The spray nozzle (24) is the spray nozzle according to any one of claims 11 to 14.

17. The application device (8) according to claim 15, characterized in that, The application device includes a seat holder (120) adapted to receive the spray nozzle (24) in an abutting manner, the seat holder (120) defining the diaphragm (54).

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