Venturi powder pump and spraying equipment comprising powder pump

Abstract

The invention discloses a Venturi powder pump and spraying equipment comprising the powder pump. The invention relates to a venturi powder gun (10) comprising a pump body (102), an injector (110) for driving a gas mounted within the pump body (102), and an ejector (112) for a mixture containing a powder product. The pump body defines a conduit (1022) upstream of the ejector (112) for the flow of the mixture. The injector (110) and the ejector (112) are straight extending along an injector axis (A110) and an ejector axis (A112), respectively, which coincide when the powder pump is in the assembled configuration (10). Indexing means (1124, 1028A) for indexing and positioning the position of rotation of the ejector (112) within the pump body (102) about the ejector axis (A112) can align the inlet of the suction chamber with a mixture flow channel (1022) defined by the pump body.

Description

Technical Field

[0001] The present invention relates to a Venturi powder pump and a powder coating apparatus, the powder coating apparatus particularly including such a powder pump. Background Technology

[0002] In the field of powder coating equipment, Venturi powder pumps are known for conveying a mixture of paint and gas drawn from a reservoir to a paint sprayer positioned close to the part to be coated.

[0003] The function of a Venturi powder pump is to draw powder coating from a reservoir, preferably using a perforated plate at the bottom of the reservoir, where the coating is fluidized by the addition of a fluidizing gas. The Venturi pump then sprays the mixture of gas and coating onto a sprayer, also known as an applicator. The performance and stability of a Venturi pump derive from the combination of two components: an injector for the driving gas (usually air) and an ejector for the mixture containing the powder product and the driving gas. The injector is designed to propel the driving gas at high speed into the suction chamber of the pump housing, where the gas expands. This expansion creates a vacuum within the suction chamber, drawing in the powder coating through a channel defined by the pump body, typically connected to the reservoir via a tube called a "suction tube."

[0004] The performance of the ejector and ejector combination is highly dependent on the correct positioning of these two components relative to each other in terms of coaxiality and relative distance.

[0005] Typically, both the ejector and the ejector are mounted within the pump body. In this case, the coaxiality and distance between the ejector and the ejector depend on the correct assembly of these two components within the pump body and the geometry of the two separate chambers within the pump body designed to accommodate them. The performance of this type of powder pump can vary so significantly for three reasons: the machining precision of the chamber within the pump body used for the ejector, the machining precision of the chamber within the pump body used for the ejector, and the precision of the assembly of the ejector and ejector within the pump body.

[0006] Furthermore, for this type of equipment, where the suction chamber that generates negative pressure due to the expansion of the driving air is directly built into the pump body, the risk of clogging is relatively high. This chamber must be thoroughly cleaned each time the powder pump injector or ejector is replaced, or even during such replacement intervals.

[0007] It is also known from documents WO2020 / 141090A1 or US2020 / 047200A1 that a portion of the ejector in a Venturi powder pump is mounted in front of the pump's injector. In this pump, the injector is supplied with drive air from the side. The drive air must turn approximately 90° in total before being injected into the upstream portion of the ejector, which generates turbulence, resulting in relatively low efficiency of the powder pump in terms of suction. Furthermore, the assembly of the ejector within the pump body may be unbalanced, potentially leading to misalignment of the ejector outlet relative to the ejector inlet, particularly caused by the rotation of the ejector-ejector assembly within the pump body about the longitudinal axis of the ejector.

[0008] Similar problems may occur with Venturi powder pumps used in other applications. Summary of the Invention

[0009] More specifically, this invention seeks to overcome these shortcomings by proposing a novel powder pump in which the ejector and the ejector are precisely positioned relative to each other and relative to the pump body.

[0010] Therefore, the present invention relates to a Venturi powder pump, comprising a pump body, an injector for driving gas, and an ejector for containing a mixture of powder products, wherein:

[0011] - When the powder pump is in the assembled configuration, the ejector and ejector are installed in the pump body;

[0012] - The pump body defines a mixture flow channel upstream of the ejector for the flow of a mixture containing the powdered product;

[0013] - The ejector is straight and extends along the ejector axis;

[0014] - The ejector and ejector are directly mounted together.

[0015] According to the present invention:

[0016] - The injector is straight and extends along the injector axis;

[0017] - When the powder pump is in its assembled configuration, the ejector axis is parallel to and coincides with the ejector axis; and

[0018] - The powder pump includes an indexing device for indexing and positioning the ejector within the pump body about the ejector axis, thereby aligning the inlet of the suction chamber with the mixture flow channel defined by the pump body.

[0019] With the help of this invention, the straight-line characteristic of the ejector means that the driving gas flow does not need to follow a circuitous path, thus making the supply of driving gas to the suction chamber more stable. Since the ejector axis is parallel to the ejector axis when the powder pump is in the assembled configuration, the mixing and driving gas flow containing the powder product are parallel, especially coaxial, thus facilitating the Venturi effect. Furthermore, the indexing device ensures the ejector is correctly positioned within the pump body, particularly to limit pressure drop and / or powder buildup at the mixing chamber or ejector inlet.

[0020] According to an advantageous, but non-mandatory, aspect of the invention, such a powder pump can be combined with one or more of the following features in any technically feasible combination:

[0021] - When the powder pump is in the assembled configuration, the ejector axis coincides with the ejector axis.

[0022] - The ejector is at least partially housed in a chamber within the pump body, and abuts against the surface of the pump body via a cone-to-cone interface centered on the ejector axis.

[0023] - When the powder pump is in the assembled configuration, the nut screwed onto the pump body applies a thrust to the ejector in a direction parallel to the ejector axis, in order to tighten the cone-to-cone interface.

[0024] - A sleeve is assembled in the tank chamber around the ejector. The sleeve, together with the ejector, defines a flow volume for dilution air, which extends downstream to the outlet of the ejector. The sleeve is provided with at least one radial channel for supplying dilution air from a distribution cavity formed around the sleeve in the tank chamber to the flow volume.

[0025] - The ejector and ejector are screwed together.

[0026] - The ejector and ejector are assembled together by a cylindrical fit.

[0027] - The ejector is made of metal, and the ejector is made of synthetic materials, preferably plastic.

[0028] - The pump body defines a drive air flow path upstream of the injector and a dilution air flow path upstream of the ejector. A connecting joint, a supply pipe for the drive air and dilution air flow paths, and at least a portion of the drive air and dilution air flow paths each extend along an axis parallel to the longitudinal axis of the mixture flow path defined by the pump body. The injector axis and the ejector axis are inclined relative to the longitudinal axis of the mixture flow path defined by the pump body at an angle other than 90°, preferably between 30° and 60°.

[0029] - The indexing device includes a shape formed on the outer peripheral surface of the ejector and a complementary shape formed on the surface defining a slot for at least partially accommodating the ejector in the pump body.

[0030] According to a second aspect, the present invention relates to a powder coating apparatus comprising a paint reservoir, a drive gas source, a dilution gas source, a powder sprayer, and a Venturi powder pump as described above. The paint reservoir is connected to a mixture flow channel defined by the pump body of the Venturi powder pump, the drive gas source is connected to a drive air inlet in the pump body, the dilution gas source is connected to a dilution air inlet in the pump body, and the ejector outlet is connected to the powder sprayer. Attached Figure Description

[0031] The invention will be better understood and other advantages of the invention will become clearer from the following description of a powder pump and powder spraying apparatus according to the principles of the invention, given only as examples and with reference to the accompanying drawings, wherein:

[0032] - [ Figure 1 ]: Figure 1 This is a schematic view illustrating the principle of a spraying apparatus according to the present invention, which includes a powder pump according to the present invention;

[0033] - [ Figure 2 ]: Figure 2 Shown on two illustrations A) and B) Figure 1 The powder pump of the device shown has a line Figure 1 A sectional view of plane II in the middle, and a larger-scale detail view of detail B in illustration A);

[0034] - [ Figure 3 ]: Figure 3 yes Figure 2 An exploded perspective view of a powder pump, wherein the pump body of the powder pump is aligned with... Figure 2 A sectional view of the same section is shown; and

[0035] - [ Figure 4 ]: Figure 4 Show Figure 2 and Figure 3 An exploded view of the ejector and ejector of the powder pump, wherein the ejector is partially removed at one of its inlets. Detailed Implementation

[0036] Figure 1 The device 2 shown in a very schematic manner includes a reservoir 4 for powder coating, also known as a "powder tank", in which the coating is fluidized by means known in itself but not shown, in particular by means of a perforated plate through which air flows.

[0037] The device 2 also includes a paint sprayer 6, which is designed to spray paint 6 onto an object O to be coated, the object being moved by a conveyor 8 along a conveyor axis A8.

[0038] Device 2 also includes a venturi powder pump 10, which is connected to the reservoir 4 via a suction tube 12, which is sometimes referred to as a "suction tube" because it is a straight element that is immersed in the reservoir 4.

[0039] In addition, the powder pump 10 is connected to the sprayer 6 via a flexible tube 14 to supply the sprayer with a mixture of powder coating and gas.

[0040] The sprayer 6 is connected to the control unit. In particular, when the sprayer 6 is electrostatic, the control unit is able to activate the electrostatic charging elements of the paint, which are not shown.

[0041] Figure 1 The sprayer 6 shown is a manual spray gun for applying powder coating. Alternatively, not shown, the sprayer 6 can be an automatic sprayer mounted on a robot that moves relative to the object O to be coated; this robot can be multi-axis or reciprocating.

[0042] The powder pump 10 is supplied with powder coating driving gas from gas source S1 and dilution gas from dilution gas source S2.

[0043] In practice, the driving gas and diluting gas are usually air.

[0044] Alternatively, other gases, such as nitrogen, can be used.

[0045] The pressures of the driving gas and the diluting gas are not necessarily the same.

[0046] The following text considers the specific case where both the driving gas and the dilution gas are air. It should be clearly stated that the following text also applies to cases where the driving gas or dilution gas is another gas.

[0047] The powder pump 10 includes a pump body 102, which is advantageously made of metal, such as steel or aluminum.

[0048] Pump body 102 defines a first guideway 1022 for allowing a mixture of powder and air from reservoir 4 to flow through suction tube 12. The first guideway extends along a longitudinal axis A1022, which may be referred to as the "suction axis".

[0049] Advantageously, when the powder pump 10 is used in the equipment 2, the longitudinal axis A1022 is vertical.

[0050] The pump body 102 also defines a second guide 1024 for the flow of drive air. A first connector 104 is mounted on an opening 1024A in the second guide 1024 and can be connected to a pipe 18 connected to the drive air source S1. The opening 1024A constitutes an inlet for drive air to enter the pump body 102.

[0051] The pump body 102 also defines a third guideway 1026 for driving the flow of air. A second connector 106 is mounted on the opening 1026A of the third guideway 1026 and can be connected to a hose 20 connected to the dilution air source S2. The opening 1026A constitutes an inlet for dilution air to enter the pump body 102.

[0052] Axis A1024 is the longitudinal axis of the upstream portion of guide 1024. Axis A1025 is the longitudinal axis of the downstream portion of guide 1024. Axis A1024 and A1025 are not parallel, which corresponds to the fact that guide 1024 forms a bend 1024C within pump body 102.

[0053] Axis A1026 is the straight longitudinal axis of guide 1026.

[0054] Axes A1022, A1024, and A1026 are parallel.

[0055] The pump body 102 further defines a chamber 1028 that extends along a longitudinal axis A1028, which is inclined at an angle α relative to axes A1022, A1024 and A1026 at a angle different from 90°.

[0056] Advantageously, the value of angle α is between 30° and 60°, preferably equal to about 45°.

[0057] Advantageously, axes A1025 and A1028 are parallel, preferably coincident.

[0058] The chamber 1028 is configured to accommodate the ejector 110, the ejector 112, and the sleeve 114.

[0059] The downstream portion 1025 of the guide 1024 leads to the bottom of the tank 1028.

[0060] Advantageously, the first guide 1022 is located upstream of the ejector 112 in the paint flow path. Advantageously, the second guide 1024 is located upstream of the injector 110 in the drive air flow path. Also advantageously, the third guide 1026 is located upstream of the ejector 112 in the dilution air flow path.

[0061] The injector 110 is straight and extends along a longitudinal axis A110, which forms an axis of symmetry with respect to the injector and constitutes the injector axis.

[0062] When the injector 110 is installed in the tank chamber 1028, the axes A110 and A1028 coincide.

[0063] like Figure 2 As can be seen in illustration A), the ejector 110 defines a channel C110 for driving airflow into an intake chamber C102 defined by the ejector 112 and into which the ejector 110 passes.

[0064] Channel C110 is straight and centered on the injector axis A110.

[0065] The ejector 112 is straight and extends along a longitudinal axis A112, which forms an axis of symmetry with respect to the ejector and constitutes the ejector axis.

[0066] Ejector 112 defines a channel C112 for the flow of a mixture of powder coating and air, centered on the ejector axis A112. O112 is the outlet of channel C112. The outlet O112 is opposite to the suction chamber C102. In the operating configuration of device 2, this outlet is connected to sprayer 6 via pipe 14.

[0067] When ejector 112 is installed in tank 1028, axes A112 and A1028 coincide.

[0068] Advantageously, when the injector 110 and the ejector 112 are in the mounting configuration installed in the tank chamber 1028, the injector axis A110 and the ejector axis A112 are tilted by the angle α relative to the axes A1022, A1024 and A1026.

[0069] In fact, when the powder pump 10 is in the assembled configuration, the ejector axis A110 and the ejector axis A112 coincide.

[0070] Sleeve 114 is mounted around ejector 112 and, together with ejector 112, defines an annular flow volume V114 for dilution air flow. Flow volume V114 is radially defined between ejector 112 and sleeve 114 relative to ejector axis A112. Flow volume V114 extends downstream to the area around outlet O112 of ejector 112.

[0071] The distribution chamber C114 is disposed within the tank 1028 surrounding elements 112 and 114. The distribution chamber 114 is supplied with dilution air from source S2 via guide 1026.

[0072] The radial channel 1142 passes radially through the sleeve 114, connecting the distribution chamber C114 and the flow volume V114, thereby allowing dilution air to flow from the guide 1026 to the outlet of the volume V114, around the outlet O112.

[0073] In the assembly configuration of the Venturi powder pump 10, the ejector 110 is completely housed within the chamber 1028, while the ejector 112 and sleeve 114 are partially housed within the chamber and protrude beyond the pump body 102, as shown below. Figure 2 As can be seen in illustration A).

[0074] Nut 116 is screwed onto the external thread 1029 of pump body 102, which is formed around the outlet O1028 of tank 1028 opposite to the first guide 1022 and the second guide 1024.

[0075] When the nut 116 is screwed onto the thread 1029, the nut 116 abuts against the outer ring 1144 of the sleeve 114, thereby pushing it toward the bottom of the slot 1028 opposite to the outlet O1028.

[0076] Furthermore, sleeve 114 defines a shoulder 1146 that axially abuts against a corresponding shoulder 1126 of ejector 112 in a direction parallel to axis A1028, thereby transmitting the thrust applied by nut 116 to ring 1144 to ejector 112. As a result, ejector 112 is pressed against the bottom of chamber 1028.

[0077] Seals isolate passages C110 and C112 and flow volume V114 from the outside of pump body 102. These seals include seal 132 carried by ejector 110, two seals 134 and 136 carried by ejector 112 and located on both sides of suction chamber C102 along ejector axis A112, and seal 138 carried by sleeve 114.

[0078] On the outer side of the portion of the sleeve 114 that protrudes from the pump body 102, there are some protrusions 1148 for connecting the supply hose 14. The external shape of the sleeve 114 can be described as a "Christmas tree connector".

[0079] A cone-to-cone interface is provided between the pump body 102 and the ejector 112.

[0080] More specifically, the truncated conical surface S1028 within the pump body 102 defines the tank 1028 near the bottom of the tank. This internal truncated conical surface S1028 is designed to accommodate the external truncated conical surface S112 of the ejector 112.

[0081] The inner truncated conical surface S1028 is centered on the axis A1028 and diverges towards the outlet O1028. The outer truncated conical surface S112 is centered on the ejector axis A112 and diverges towards the outlet O112.

[0082] The internal truncated conical surface S1028 is truncated at its intersection with the first guide channel 1022.

[0083] The cone-to-cone interface of surfaces S112 and S1028 allows the ejector axis A112 to be precisely aligned on axis A1028 and to precisely position the ejector 112 along axis A1028.

[0084] Nut 116 is used to apply a thrust to ejector 112 in a direction parallel to ejector axis A112, tightening the cone-to-cone interface between truncated conical surfaces S112 and S1028. This makes the positioning of ejector 112 in the chamber 1028 more reliable.

[0085] Furthermore, the ejector 110 and the ejector 112 are directly mounted together. Advantageously, the ejector 110 is screwed into the ejector 112 opposite to the outlet O112. For this purpose, the ejector 110 is provided with an external thread 1102, which mates with a corresponding internal thread 1122 of the ejector 112 provided at the ejector inlet E112.

[0086] The outer peripheral surface of the injector 110 is provided with grooves 1104, which facilitate gripping the injector and applying tightening torque when the elements 110 and 112 are screwed together.

[0087] Alternatively, other types of textures, such as knurling, can be used instead of groove 1104.

[0088] Screw components 110 and 112 together until the shoulder 1106 of the ejector 110 abuts against the annular surface S'112 of the ejector 112 surrounding the inlet E112, thereby ensuring precise positioning of the ejector 110 relative to the ejector 112 and the suction chamber C102 along the axis A1028.

[0089] To ensure that the angular orientation of the ejector 112 around axis A1028 allows for a seamless fit between the guide channel 1022 and the suction chamber C102, an indexing device is provided for indexing and positioning the position of the ejector 112 within the pump body 102, rotating around the ejector axis A112. The indexing device aligns the inlet E102 of the suction chamber C102 with the guide channel 1022.

[0090] The indexing device includes a convex relief, in this example a lug 1124, which is formed on the outer peripheral surface S''112 of the ejector 112. The lug 124 extends the outer peripheral ring 1125 of the ejector 112 locally within a relatively small angular range (about 5 to 10°).

[0091] In addition, a concave portion, in this example a partial extension 1028A of the chamber 1028, is provided to accommodate the convex portion 1124 when surfaces S112 and S1028 are in mutual surface contact. Advantageously, the shape of the extension 1028 is complementary to the shape of the lug 1124. The lug 1124 engages in the extension 1028A and serves to fix the angular position of the ejector 112 rotating about the ejector axis A112 and the axis A1028 of the chamber 1028, thereby ensuring that the inlet E102 of the suction chamber C102 is correctly positioned relative to the guide 1022. This minimizes the risk of pressure drop and paint buildup at the inlet of the suction chamber C102.

[0092] In the example shown in the accompanying drawings, when the ejector 110 and the ejector 112 are installed and secured in the chamber 1028, the lug 1124 is fully accommodated in the extension 1028A. Alternatively, only a portion of the lug 1124 may be accommodated in the extension 1028A.

[0093] According to a variation of the invention (not shown), a convex shape is provided on the pump body 102 and a concave shape is provided on the ejector 112, thereby serving as an indexing device for indexing and positioning the position of the ejector 112 rotating about the ejector axis A112 within the pump body 102.

[0094] Components 110, 112, and 114 are reversibly installed in tank 1028. Therefore, when maintenance operations are required on powder pump 10, nut 116 can be unscrewed to remove the sub-assembly formed by components 110, 112, and 114 from tank 112, and then sleeve 114 can be separated from components 110 and 112.

[0095] When component 112 wears down due to the passage of powder coating mixed with driving air, components 110 and 112 can be unscrewed from each other and component 112 can be replaced.

[0096] In this respect, ejector 110 is preferably made of metal, while ejector 112 is preferably made of a synthetic material, such as plastic, like high-density polyethylene or, for example, high-molecular-weight polyethylene sold under the brand name Polystone. Alternatively, other synthetic materials may be used for ejector 112.

[0097] The ejector is made of a more wear-resistant material than the ejector 112, and its channel C110 allows unloaded air to pass through, unlike channel C112 which allows a mixture of air and paint to pass through. Thus, the ejector 110 has a longer service life than the ejector 112.

[0098] The value of the angle α, which is different from 90°, allows the powder pump 10 to have good compactness in the lateral direction of the axis (i.e. axis A1022) perpendicular to the direction in which the paint is sucked into the reservoir 4.

[0099] According to a variation of the invention (not shown), the powder pump according to the invention can be used in equipment other than powder coating equipment.

[0100] According to a variation of the invention (not shown), the ejector 110 and the ejector 112 are directly mounted together by a cylindrical fit, for example by a press fit, without the need to be screwed together.

[0101] Any feature described above with respect to one embodiment or variation may be applied to other embodiments and variations, provided that it is technically feasible.

Claims

1. A venturi powder pump (10) comprising a pump body (102), an eductor (110) for driving a gas and an ejector (112) for containing a mixture of a powder product, wherein: - the eductor (110) and the ejector (112) are mounted in the pump body (102) when the venturi powder pump is in an assembled configuration (10); - the pump body defines, upstream of the ejector (112), a mixture flow-through duct (1022) for the flow-through of the mixture containing the powder product; - the ejector (112) is straight and extends along an ejector axis (A112); - the eductor (110) and the ejector (112) are mounted directly one into the other; characterized in that: - the eductor (110) is straight and extends along an eductor axis (A110); - the eductor axis (A110) coincides with the ejector axis (A112) when the venturi powder pump is in the assembled configuration (10); and - the venturi powder pump comprises indexing means (1124, 1028A) for indexing the position of the rotation of the ejector (112) within the pump body (102) around the ejector axis (A112) so as to align the inlet (E102) of the suction chamber (C102) with the mixture flow-through duct (1022) defined by the pump body.

2. The venturi powder pump according to claim 1, wherein the eductor axis (A110) coincides with the ejector axis (A112) when the venturi powder pump is in the assembled configuration (10).

3. The venturi powder pump according to claim 1, wherein the ejector (112) is at least partially housed in a slot chamber (1028) of the pump body (102) by abutting a surface (S1028) of said pump body with a conical interface centered on the ejector axis (A112).

4. The venturi powder pump according to claim 3, wherein a nut (116) screwed onto the pump body (102) exerts a thrust force on the ejector (112) parallel to the ejector axis (A112) in a direction tightening the conical interface when the venturi powder pump is in the assembled configuration (10).

5. The venturi powder pump according to claim 3 or 4, wherein: - a sleeve (114) is mounted in the slot chamber (1028) around the ejector (112); - the sleeve and the ejector define together a flow-through volume (V114) of dilution air which opens downstream to around the outlet (O102) of the ejector; and - the sleeve is provided with at least one radial passage (1142) for feeding the flow-through volume with dilution air from a distribution chamber (C114) formed around the sleeve in the slot chamber (1028).

6. The venturi powder pump according to any one of claims 1 to 4, wherein the eductor (110) and the ejector (112) are screwed together.

7. The venturi powder pump according to any one of claims 1 to 4, wherein the eductor (110) and the ejector (112) are assembled together by cylindrical fit.

8. The Venturi powder pump according to any one of claims 1 to 4, wherein the injector (110) is made of metal and the ejector (112) is made of synthetic material, preferably plastic.

9. The Venturi powder pump according to any one of claims 1 to 4, wherein, - the pump body (102) defines a drive air flow passage (1024) upstream of the injector (110) and a dilution air flow passage (1026) upstream of the ejector (112); - the junctions (104, 106) for connecting the tubes (18, 20) supplying the drive air flow passage (1024) and the dilution air flow passage (1026), and at least part of said drive air flow passage and dilution air flow passage each extend along an axis (A1024, A1026) parallel to the longitudinal axis (A1022) of the mixture flow passage (1022) defined by the pump body; - the injector axis (A110) and the ejector axis (A112) are inclined at an angle (a) different from 90° with respect to the longitudinal axis (A1022) of the mixture flow passage (1022) defined by the pump body, said angle being preferably comprised between 30° and 60°.

10. The Venturi powder pump according to any one of claims 1 to 4, wherein the indexing means comprise a profile (1024) formed on the outer peripheral surface (S"112) of the ejector (112) and a complementary profile (1028A) formed on the surface (S1028) of the slot (1028) delimiting the slot chamber (1028) for at least partially housing the ejector in the pump body.

11. A powder spraying apparatus (2) comprising a paint reservoir (4), a drive gas source (SI), a dilution gas source (S2), a powder spray (6) and a Venturi powder pump (10) according to any one of the preceding claims, wherein the paint reservoir (4) is connected to the mixture flow passage (1022) defined by the pump body (102) of the Venturi powder pump (10), the drive gas source (SI) is connected to the drive air inlet (1024A) in the pump body, the dilution gas source (S2) is connected to the dilution air inlet (1026A) in the pump body and the outlet (01112) of the ejector (112) is connected to the powder spray (6).

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