EP2986857A1

EP2986857A1 - Venturi pump and facility for applying paint coatings

Info

Publication number: EP2986857A1
Application number: EP14719684.4A
Authority: EP
Inventors: Christophe Pravert
Original assignee: Sames Technologies SAS
Current assignee: Sames Kremlin SAS
Priority date: 2013-04-17
Filing date: 2014-04-16
Publication date: 2016-02-24
Anticipated expiration: 2034-04-16
Also published as: FR3004767B1; CN105283675B; WO2014170374A1; CN105283675A; KR102217672B1; EP2986857B1; KR20150142692A; FR3004767A1; US9636695B2; US20160052001A1

Abstract

This Venturi pump (2), which can be used for sucking powder from a supply (A), diluting same, then feeding it to a gun (D) via a conveyor pipe, comprises an outer body (20), at least one powder suction duct (22), at least two air connections (24, 28), of which a first air connection (24) is capable of supplying an injector (284) to create a vacuum inside the suction duct (22) and a second air connection (28) is capable of supplying a dilution air circuit separate from the powder flow, at least one powder outlet nozzle (26), centred on an axis of diffusion (Y26), the inlet of which is located downstream from the first air connection (24) and the suction duct, at least one protection barrier (282), disposed inside the dilution air circuit and at least one outlet tip (284) of the dilution circuit, disposed around the nozzle (26) and also connected to the conveyor pipe (T). The protection barrier comprises a non-return valve (282) that radially surrounds the nozzle (26).

Description

VENTURI EFFECT PUMP AND COATING APPLICATION FACILITY

PAINT

The present invention relates to a powder pump of Venturi technology used, in particular in a method of electrostatic powder coating paint application. A pump with Venturi effect is a relatively simple and inexpensive organ. This body is based on the Venturi effect which consists of creating a vacuum by injecting air at high speed in order to suck powder from a reservoir that can contain a bed of fluidized powder and then convey it to to a pneumatic or electrostatic applicator by means of a pipe adapted to the transport of powder. In order to more easily suck up the powder at the base of the tank, air is injected into the tank to fluidize the powder. Depending on the supply distance between the Venturi effect pump and the applicator and the length of the transport hose, which can vary between three and fifteen meters, this type of pump can be used to obtain paint flows from the pump. order of fifty to five hundred grams per minute.

A pump with a Venturi effect most often comprises a powder suction pipe immersed in the powder tank, an air connection which makes it possible to create a vacuum within the suction duct and an ejector which makes it possible to evacuate the mixture. air / powder inside a transport hose and towards the electrostatic applicator or, more simply, the gun.

In order to allow optimum transport in the dilute phase without pulsations, that is to say to ensure a continuous flow of powder along the transport pipe, it is known to add pump injection means to the pump. an additional air called "dilution" downstream of the mixture of air and powder and upstream of the transport pipe. A pump of this type is therefore most often powered by a pneumatic device generating two air circuits, an "injection" air circuit and a "dilution" air circuit. The pneumatic organ regulates the pressure or the air flow mixed with the powder. Regardless of the mode of regulation chosen, the pneumatic injection and dilution air supply members are sensitive to the rise of powder that can be observed during transient pumping phases or during the cleaning phases. It has been found that the dilution air circuit is much more sensitive to these rising powder. Indeed, it is sometimes inactive in the pumping phase when the injection air flow alone can ensure a transport without pulsations. Thus, the dilution air supply circuit is at zero relative pressure, whereas a pressure of the order of several tens of millibars prevails at the outlet of the pump in the mixture to be transported. As a result, a powder-fed reverse current flows to the pneumatic members of the module. Similarly, the cleaning phases are also conducive to the rise of powder in the dilution circuit.

To remedy this problem, it is known to protect the pneumatic control modules by incorporating protective barriers. These protection barriers can be integrated at the level of the pneumatic module itself, or in the supply circuits, between the module and the pump, or at the level of the injection air supply and dilution connections. the pump. These protective barriers generally consist of a porous media or a non-return valve such as for example a ball valve or a membrane valve.

The use of a non-return valve housed in the air supply connection makes the connection expensive and cumbersome. The use of a porous media provides an effective protective barrier, since air can flow through the pores of the media, but the pores are thin enough so that the powder can not pass through the media. On the other hand, after a certain period of operation, the inverse air flow loaded with powder has the effect of slowly closing the pores of the porous media by incrustation of the grains of powder in the material. This encrustation results in a decrease in the passage of air and therefore a loss of efficiency during pumping. It is then necessary to replace this part after a certain period of operation, which generates an additional cost of maintenance for the user. Thus, although the porous media is inexpensive in manufacture and offers effective protection against powder returns, it is an additional wear part and leads to more expensive maintenance.

It is these drawbacks that the invention intends to remedy more particularly by proposing a Venturi effect pump provided with an effective protective barrier and not constituting a wear part.

For this purpose the invention relates to a Venturi effect pump, for sucking a powder from a reserve, to dilute it and then to convey it to a gun via a transport pipe. This pump comprises an external body, at least one powder suction pipe, at least two air connections, among which a first air connection is able to supply an air injector to create a depression in the duct. a second air connection is adapted to feed a dilution air circuit separated from the powder flow, at least one powder outlet ejector, centered on a diffusion axis, the inlet of which is situated downstream of the first air connection and the suction duct, at least one protective barrier arranged inside the dilution of air and at least one outlet end of the dilution air circuit, disposed around the ejector and also connected to the transport pipe. According to the invention, the protective barrier comprises a non-return valve which radially surrounds the ejector.

Thanks to the invention, the pneumatic air supply members are protected from the return of powder economically since the protective barrier does not constitute a wear part and therefore does not need to be replaced during the operating period of the Venturi pump.

According to non-mandatory advantageous aspects of the invention, a Venturi effect pump may incorporate one or more of the following features, taken in any technically permissible combination:

- The non-return valve is a lip seal, radially disposed between the ejector and the outlet tip.

Alternatively, the non-return valve comprises a ring bearing an O-ring seal.

- The ring comprises a groove which widens inwardly radially to the axis of diffusion and which comprises two chamfers, between which is disposed the seal in the closed position of the groove.

- Alternatively, the ring comprises a groove which widens outwardly radially to the diffusion axis and which comprises two chamfers, between which is disposed the seal in the closed position of the groove.

- The seal has a section of diameter greater than or equal to the minimum opening of the groove.

- During the passage of the injected air upstream, the seal is deformed elastically to move from a first position where it closes the groove to a second position where it does not close the groove.

- The ring comprises a shoulder located radially inside the seal.

- The O-ring is in its second position, bearing against the shoulder.

- The ring and the body of the pump are monoblock.

- The outlet end and the ring are monoblock.

- The ejector and the ring are monoblock.

The invention also relates to an installation for applying a powder coating product, comprising a reservoir, in which the powdery product is fluidized, a pneumatic supply module, supplying an "injection" air circuit, and a fuel injection circuit. 'air' of dilution, a pump with Venturi effect powered by the module pneumatic supply and conveying coating product from the reservoir to a gun while the Venturi effect pump is as previously described.

The invention will be better understood and other advantages thereof will appear more clearly in the light of the following description of an embodiment of a pump Venturi effect according to its principle, given only as a example and with reference to the accompanying drawings in which:

FIG. 1 is a front view of a Venturi effect pump according to the invention,

FIG. 2 is a section along the line 11-11 of FIG. 1;

FIG. 3 is a view on a larger scale of the box III of FIG. 2,

FIG. 4 is a view similar to FIG. 3 when a seal of the pump is in a second position different from that shown in FIG.

FIGS. 1 and 2 show a Venturi effect pump 2 intended to be used in a powder coating product application installation. The Venturi effect pump 2 extends along a main axis Y2 and comprises an outer body 20. The outer body 20 has a plurality of openings for receiving different inlet and outlet ducts. Among the inlet ducts, there is a first suction duct 22 of generally cylindrical shape and centered on an axis Z22. The suction duct 22 is connected upstream to a tank A which is not shown and which contains a bed of fluidized powder.

The Venturi effect pump 2 also includes at its inlet a first air injection connector 24. The connector 24 is connected via a duct 25 to a pneumatic supply module B. On the end portion of the connector 24, there is an injector 242 which extends along an axis Y242, the axis Y242 coinciding with the Y2 axis defined above. The injector 242 is located in the extension of the fitting 24 whose section is narrowed so as to accelerate the air at the end of the connector 24 to create a vacuum at the outlet of the injector 242. This is the Venturi effect . In this case, the injector 242 belongs to the connector 24. In a variant, the injector 242 and the connector 24 are two different parts. The air injector 242 opens onto an area 244 located at the downstream end of the suction duct 22. A depression is therefore created in this zone 244, which tends to suck the powder from the tank A to the zone 244 in the direction of the arrow F ₀ in FIG. 2. At the zone 244, there is the mixing between the air injected by the connection 24 and the powder sucked into the suction duct 22. The mixture of air and powder is propelled downstream of the connection 24, that is to say along the axis Y242 and the right to the left in Figure 2. The air / powder mixture thus reaches an ejector 26 which extends along a Y26 scattering axis, the Y26 axis and the Y242 axis being merged. The ejector 26 has a downstream end portion, that is to say located on the left side of the ejector 26 in Figure 2, an inner section greater than that of the upstream part, or the right part in Figure 2. The ejector 26 has the shape of a nozzle. The fact of using a nozzle shape makes it possible to increase the pressure of the air / powder mixture at the outlet. This makes it easier to route the air / powder mixture to an electrostatic applicator D, especially a gun, through the transport pipe.

The Venturi effect pump 2 also includes as input a second air supply connector 28, centered on an axis Z28 which is perpendicular to the axis Y2. It feeds a dilution air circuit, this dilution circuit V28 being separated from the powder flow. The injection of the dilution air into the air / powder mixture takes place downstream of the first injection, intervened upstream via the injector 242. This supply duct 28 is also connected to the pneumatic supply module B by a duct 29. The pneumatic supply module B thus provides air in the two connections 24 and 28. The connector 24 is a supply connection called "injection" while the supply connection 28 is a conduit of diet called "dilution". The air injected inside the supply connection 28 passes inside an outlet nozzle 284, this outlet nozzle 284 is disposed around and coaxially with the ejector 26 and having externally projections: therefore a "fir" connection. The passage of the dilution air is annular between the outlet nozzle 284 and the ejector 26.

The outlet nozzle 284 and the ejector 26 are connected downstream, that is to say on the left in FIG. 2, to a transport pipe T which makes it possible to route the air / powder mixture to the electrostatic applicator or application gun D for coating a piece of paint. The additional air injected into the connection 28 makes it possible to reduce the pulsations that may appear during the transport of the air / powder mixture. These pulsations occur if the transport speed is not sufficient in the pipe resulting in insufficient transport air flow. The diameter of the transport pipe T is optimized according to the powder flow rate to be supplied and the transport distance to be made from the Venturi effect pump 2 to the electrostatic applicator D.

The volume present between the outlet nozzle 284 and the ejector 26 is an annular volume V284 which constitutes a dilution chamber.

The use of additional air or dilution air at connection 28 is actually optional. Indeed, this dilution air supply is sometimes inactivated in the pumping phase when the injection air flow alone allows to ensure a transport without pulsations. In this particular case, the pressure that prevails within the volume V284 is substantially equal to the pressure at the outlet of the ejector 26 which is of the order of a few millibars. This pressure is a consequence of the air / powder flow downstream in the transport pipe. Side pneumatic supply module B, the conduit 29 is at zero pressure when the dilution feed is inactivated. At its other end, the conduit 29 is subjected to a pressure substantially equal to that prevailing in the volume V284. Thus part of the air / powder mixture is likely to reach the pneumatic supply module B.

This is why the dilution air circuit is much more sensitive to the rising of powder. In order to protect the pneumatic supply module B from the powder lifts, the Venturi effect pump 2 further comprises a nonreturn valve 282. This non-return valve 282 ensures, on the one hand, the passage of air freely from upstream to downstream, that is to say, from the supply conduit 28 to the outlet nozzle 284, and secondly, the blocking of the air / powder mixture in the reverse. In order to stop as close as possible the infiltration of the air / powder mixture inside the dilution air circuit V28, the nonreturn valve 282 is placed as close as possible to the outlet of the air / powder mixture. Since it is impossible to position this check valve 282 in the connector "fir", it has been chosen to position it directly at the outlet of the supply conduit 28. The check valve 282 is generally annular shape and is advantageously arranged coaxially around the ejector 26. Thus, the air injected into the dilution circuit is homogeneously distributed in the dilution chamber V284 and the mixture of this dilution air with the powder, at the outlet of the ejector 26 is improved.

More precisely, and as visible in FIG. 3, the check valve 282 comprises a seal ring 2820 and a seal 2822. A volume V2820 is defined as the volume of passage of the air from the pneumatic module. P to the dilution chamber V284. This volume includes in particular the channels 2826 to the passage of air in the valve 282 and the throat 2824. Thus, the dilution air circuit V28 is constituted by the dilution chamber V284 and the volume V2820 corresponding to the volume borrowed by the air upstream of the V284 dilution chamber. The ring 2820 comprises several air passage channels 2826, one of which is visible in FIG. 3. These channels 2826 are installed at the outlet of the supply duct 28, extend parallel to the diffusion axis Y26 and open onto a groove 2824 formed by two chamfers 2828. The channels 2826 open on the narrower part of the groove, that is to say where the gap, taken parallel to the axis Y26, between the chamfers 2828 is the most low. In other words, the channels 2826 are positioned radially on the axis Y26, on the outside 2824. The groove 2824 extends over the entire periphery of the seal ring 2820, while the air passage channels 2826 are regularly distributed around the diffusion axis Y26. This allows air injection which is homogeneous in the groove 2824 and in the dilution chamber V284. The groove 2824 widens, radially to the axis Y26, ie along a central axis Z2824, inwards. The two chamfers 2828 are arranged symmetrically with respect to the central axis Z2824 and are inclined at an angle of about 45 ° with respect to this central axis. Between the two chamfers 2828 is disposed an O-ring 2822. The seal 2822 has an annular section whose diameter D1 is greater than the minimum opening distance D2 of the groove 2824. Thus, the seal 2822 is able to close the throat 2824.

The air injected into the passage 2826 tends to compress the seal 2822 in a direction radial to the Y26 axis and directed inwardly. This direction is represented by the arrow F1 in FIG.

In order to limit the compression of the O-ring 2822 and that it is peeled off, a shoulder 2829 is provided in the ring 2820 and is radially located inside the O-ring 2822. During the passage of the injected air in upstream, the seal is elastically deformed so as to move from a first position shown in Figure 3 where it closes the groove 2824 to a second position shown in Figure 4 where it is optionally bearing against the shoulder 2829 of the ring. Indeed, in the case where the inlet air pressure is too low, the seal is compressed radially but does not reach the shoulder 2829. However, the air can flow along the chamfers 2828, as represented by the arrows F2 in FIG.

On the contrary, assuming that an air / powder mixture arrives in the opposite direction, that is to say from left to right in FIG. 3, the seal 2822 is expanded, it is that is, pressed against the chamfers 2828 and closes the groove 2824. The nonreturn valve 282 is designed so that it has the least possible powder retention zones. In addition, the valve 282 is cleaned simply during the passage of the dilution air because the entire seal is bathed by the air flow.

Indeed, a rise of powder from the ejector 26 in the dilution chamber V284 and even to the O-ring 2822, causes deposits of powder residues on the walls of the valve and on the seal. When injecting the dilution air, the air tends to sweep down these powder residues downstream. This self-cleaning function is particularly advantageous since it avoids a maintenance operation of removing and cleaning the check valve 282. In contrast with the valves of the art prior, the nonreturn valve 282 does not therefore constitute a wear part of the pump 2.

The valve 282 is advantageously disposed coaxially with the ejector 26, thus limiting the compressible volume V284 which separates the valve 282 from the powder outlet. This makes it possible, on the one hand, to facilitate the cleaning of the dilution chamber V284 and, on the other hand, to limit the infiltrations of the air / powder mixture arriving at the outlet of the ejector 26 in the volume V284.

The outlet tip 284 is made of a generally electrically conductive material and caps the ejector 26 to its downstream end. Thus, the outlet nozzle 284 is practically indestructible and makes it possible to discharge a portion of the triboelectric charges present on the ejector 26. The passageways for the passage of the powder, namely the suction duct 22 and the ejector 26, are made of suitable plastic, so as not to polymerize the powder on contact.

When connecting the transport pipe T and the outlet of the pump 2, consisting of the ejector 26 and the outlet nozzle 284, the dilution air is therefore added to the mixture of air and powder injected upstream. The injection air and dilution air flows add up and form a total air flow rate of the powder coating product. A good adjustment of the transport air flow ensures a transport without pulsations, that is to say smoothly and at a constant rate. In this way, the application of the powder coating product is uniform. A seal 202 seals the dilution air supply duct relative to the outside.

As a variant not shown, the seal ring 2820 and the body 20 of the pump 2 are monobloc. The ring 2820 can also be integrated in the outlet nozzle 284 or in the ejector 26.

The nonreturn valve 282 can be mounted fixed or removable on the pump 2.

According to another variant, it is conceivable to use a lip seal, integrated directly into the dilution chamber, and whose lip preferably deforms in one direction. The direction of deformation of the lip being that of the passage of the dilution air. It is this unilateral deformation of the lip that provides the anti-return function.

According to another variant, the installation comprising the Venturi effect pump 2 uses a non-electrostatic application gun, for example of the pneumatic type.

According to another variant, there is only one air passage channel 2826 which has an annular shape in the seal ring 2820. According to another variant, the groove 2824 widens, radially to the axis Y26, towards the outside. Thus the channels 2826 are positioned, radially to the axis Y26, inside the groove 2824 and open on the narrowed portion of the groove 2824. When injecting the air upstream, the seal 2822 is therefore radially expanded to allow air to enter the throat 2824.

The variants and embodiments mentioned above may be combined to give new embodiments of the invention.

Claims

1. - Pump (2) with Venturi effect, to suck a powder from a reserve (A), to dilute it, then to convey it to a gun (D) via a transport pipe (T) , this pump comprising:

an external body (20),

at least one pipe (22) for extracting powder,

at least two air connections (24, 28), among which a first air connection (24) is able to feed an injector (242) of air to create a vacuum within the suction duct (22); ) and a second air connection (28) is adapted to feed a circuit (V28) of dilution air separated from the powder flow,

at least one powder outlet ejector (26), centered on a diffusion axis (Y26), the inlet of which is located downstream of the first air connection (24) and the suction duct (22) ,

- at least one protective barrier (282) disposed within the dilution air circuit and,

at least one outlet end (284) of the dilution air circuit (V28) disposed around the ejector (26) and also connected to the transport pipe (T), characterized in that the protective barrier comprises a nonreturn valve (282) radially surrounding the ejector (26).

2. - Pump according to claim 1, characterized in that the non-return valve (282) is a lip seal, radially disposed between the ejector (26) and the outlet nozzle (284).

3. - Pump according to claim 1, characterized in that the non-return valve (282) comprises a ring (2820) carrying an O-ring seal (2822). 4. Pump according to claim 3, characterized in that the ring (2820) comprises a groove (2824) which widens inward radially to the diffusion axis (Y26) and which comprises two chamfers (2828) , between which is disposed the seal (2822) in the closed position of the groove. 5- pump according to claim 3, characterized in that the ring (2820) comprises a groove (2824) which widens outwardly radially to the diffusion axis (Y26) and which comprises two chamfers (2828), between which is disposed the seal (2822) in the closed position of the groove.

6. Pump according to one of claims 4 and 5, characterized in that the seal (2822) has a diameter section (D1) greater than or equal to the minimum opening (D2) of the groove (2824). ). 7.-Pump according to one of claims 4 to 6, characterized in that during the passage of the injected air upstream, the seal (2822) is deformed elastically (F) to pass a first position (Figure 3) where it closes the groove (2824) at a second position (Figure 4) where it does not close the groove. 8. Pump according to one of claims 3 to 7, characterized in that the ring

(2820) comprises a shoulder (2829) located radially inside the seal (2822).

9. - Pump according to one of claims 7 and 8, characterized in that the O-ring (2822) is in its second position, bearing against the shoulder (2829).

10. - Pump according to one of claims 3 to 9, characterized in that the ring (2820) and the body (20) of the pump are monobloc.

1 1 - Pump according to one of claims 3 to 10, characterized in that the outlet tip (284) and the ring (2820) are monobloc.

12. Pump according to one of claims 3 to 1 1, characterized in that the ejector (26) and the ring (2820) are monobloc. 3. A powder coating product application installation, comprising:

a reservoir (A) in which the powdery product is fluidized,

a pneumatic supply module (B) supplying an "injection" air circuit and a "dilution" air circuit, a Venturi effect pump (2) fed by the pneumatic supply module (B) and conveying coating product from the tank (A) to a gun (D),

characterized in that the Venturi effect pump is a pump according to one of claims 1 to 12.