FR2720662A1 - Cleaner using abrasive particles delivered by compressed air - Google Patents

Abstract

The cleaner consists of a compressed air source (100), a container (C) for the abrasive powder, and a projection head (106) for delivering very fine abrasive particles (0-200 micrometers) towards the surface being cleaned. The projection head is connected to the compressed air source by a duct with a feed section (204), a mixing chamber (6) and an outlet (206). The container (C) for the powder has a feed pipe (3) with convergent walls and a control valve connecting it to the mixing chamber. The projection head (106) contains a disc with fine holes for the powder particles to pass through. The holes measure from 400 micrometres to 4mm in diameter and are kept constantly clear by the compressed air flow. The compressed air feed duct has a pressure regulator (400), and the compressed air source (100) is connected to the abrasive powder container (C) by a duct (402) with a second pressure regulator (403), so that the air can be delivered at difference pressures to the container and mixing chamber. The powder feed pipe (3) the mixing chamber (6) and a diffusion chamber (7,70) after it are made from a synthetic material.

Description

MIXTURE DISPENSING DEVICE
COMPRESSED AIR AND POWDER
The present invention relates to a device for dispensing a mixture of compressed air and powder, and more precisely a powder with very fine particle size.

 In several areas of the art, it is necessary to deliver a mixture of compressed air and powder to a user device.

 This is particularly the case in the field of cleaning a soiled support, for example the facade of a building, using fine abrasive particles.

 In its international patent application WO-93 11908, the applicant has proposed a micro-cleaning installation for a support which uses a rotary spraying head of the air / powder mixture. The projection is done through a multitude of nozzles having a small passage section, the diameter, for information, is between 400 micrometers and 4 millimeters.

 The particle size of the abrasive particles is less than 200 micrometers.

 Traditionally, the supply of abrasive particles to the device is done by means of sandblasting equipment, commonly called a sandblaster, comprising a powder storage tank which is connected to a source of compressed air, generally a compressor. ; passing through the tank, the compressed air becomes charged with particles, which are then transferred via a flexible hose to the projection apparatus.

 If such a material is satisfactory with relatively large particles, and large diameter projecting nozzles, we observe with very fine particle size powder, and correlatively with very small section nozzles, clogging problems, which lead to a malfunction. quick installation.

 In addition, the particle flow is irregular and does not allow to obtain a homogeneous flow. This is particularly the case when the arrival of the air / powder mixture is frequently stopped, when the operation is restarted.

 The present invention aims to overcome the above-mentioned drawbacks by proposing a device which makes it possible to obtain a fine and regular flow, making it possible to use the abrasive temporarily and selectively, without the problem of clogging of the pipes or of the nozzles.

 Another objective of the invention is to propose a device of simple design.

These results are achieved, in accordance with the present invention, thanks to the fact that the device comprises, from upstream to downstream in the direction of movement of the powder.
a) a powder supply duct, with a substantially frustoconical converging wall, into which the powder flows from a storage tank
b) a valve for closing the outlet orifice of the supply duct, capable of selectively occupying an open position or a closed position of said orifice
c) a transfer duct
d) a powder mixing chamber with compressed air
e) a diffusion chamber closed by a filtering grid provided with a multitude of passage holes of small section, slightly greater than the section corresponding to the particle size of the powder;
f) an outlet pipe for the air / powder mixture.

Furthermore, according to a certain number of advantageous, non-limiting characteristics
- the diffusion chamber is composed of two coaxial parts, with frustoconical wall, separated by the filtering grid, one divergent, upstream of the grid, and the other convergent, downstream of the grid
- the supply duct is substantially vertical, with its outlet orifice directed downwards, and is provided with deflectors limiting the packing of the powder
- the device comprises a vibrator arranged in the exit zone of the supply duct
- said valve and / or said vibrator are pneumatically operated
- the device consists of a plastic housing containing the various conduits and chambers for the passage of powder and air
- The device comprises a purge system comprising a compressed air supply channel at said outlet orifice
- A series of removable and interchangeable tips is provided, which have outlet openings of different finesse, capable of being placed selectively at the base of said supply conduit.

 The device finds particular application for feeding an apparatus for projecting abrasive particles for cleaning a surface; in this case, the device comprises projection nozzles whose passage section is greater than that of the holes of the filtering grid.

 Advantageously, this device is with a rotary head driven by a pneumatic motor and the control of the latter, the control of said valve and the supply of compressed air to said mixing chamber are done from a common source of compressed air. , such as a compressor.

 Particularly advantageously, it is possible to supply compressed air to the device while said valve is in the closed position.

 Other characteristics and advantages of the invention will appear from the description and the appended drawings which represent a preferred embodiment.

On these drawings
- Figure I shows the device in section;
- Figure 2 is a diagram of an installation for projecting abrasive particles using a device according to the invention.

 In FIG. 1, reference has been made to a housing made of synthetic material, composed of two parts 1A and 1B fixed to each other, the assembly constituting a compact block.

 As a material, it is possible to use a polyamide such as that commonly designated by the registered trademark "NYLON".

 This material, in fact, has both good quality of abrasion resistance and avoids condensation phenomena which occur on metal walls.

 The device 1 comprises a connector 10 on which a nozzle 11 is fitted which is integral with the powder storage tank C, which is symbolized by a strong broken line.

 The connector 10 is tubular and opens into a coaxial conduit 3, called the supply conduit.

 It is a chamber with a frustoconical wall, of vertical axis, the outlet opening 30 of which faces downwards. At the inlet of the conduit 3 is mounted a shutter 2 with manual control by means of a lever 20.

As an indication, the frustoconical wall of conduit 3 has an apex angle u of the order of 20.

 Inside the duct 3 are mounted deflecting vanes 31 arranged in staggered rows and slightly inclined in the direction of flow, by gravity, of the powder from top to bottom, towards the outlet orifice 30. Their function is to absorb part of the weight of the powder mass, avoiding settling, and promote the flow of particles.

 At the lower part of the duct 3 is mounted a vibrator 9 with pneumatic control, the function of which - well known per se - is also to encourage the passage of particles in the outlet zone 30, of the smallest diameter.

 This lower part of the conduit 3 is occupied by a frustoconical end piece 32, removable and interchangeable. One can provide a series of tips having more or less fine outlet orifices 30, for example with a diameter ranging from 0.5 to 5 millimeters. Thus it is always possible to obtain a regular fluid flow by choosing the appropriate nozzle, the best suited to the nature and / or the particle size of the powder.

It would be difficult, if not impossible, to obtain a regular flow by means of a flow control screw of the "screw-needle" type (commonly used in sandblasters) partially blocking the outlet orifice.

 At this level opens a channel 12, 12 ′ intended to allow the purging of the powder capable of clogging the orifice 30. For this, it is sufficient to connect the channel to a source of compressed air, which has the effect of expelling by blowing the powder cap.

 The outlet orifice 30 is selectively closable by means of a butterfly-type valve 4, having a pivoting obturator pallet 40 in the form of a disc.

 Valve 4 is pneumatically operated.

 It is normally closed, and opens when it is supplied with compressed air.

 The device 1 is provided with a conduit 6 called the mixing chamber. It is a horizontal cylindrical duct having a tapped end zone 60, for the adaptation of a hose connector for supplying compressed air into the duct 6.

 The latter is located below and directly above the outlet orifice 30, with which it communicates by a transfer duct 5, of generally frustoconical shape inclined downward and downstream if we consider the direction of displacement of the compressed air flow in the duct 6.

In Figure I we symbolized by the arrows F1 and F2
respectively, the displacement of a part of the stern in the duct of
transfer 5 and on the other hand of the compressed air in the duct 6.

There is therefore a mixing of the powder in line 6
and air.

The conduit 6 opens at its downstream end into a space
called diffusion chamber.

It is a room composed of two frustoconical parts
7, 70 coaxial, of vertical axis, between which is inserted a filtering grid 8.

The lower part, and upstream 7, diverges towards the grid, while
the upper part, and downstream 70, converges from the grid.

The fitrante grid is a disc of material very resistant to
abrasion, for example in tungsten carbide, pierced with a plurality of cylindrical holes 80 of very small diameter, nevertheless greater than the largest dimensions of the powder particles.

 As an indication, the particle size of the powder is from 0 to 200 micrometers, and the holes 80 have a diameter of between 300 and 800 micrometers.

 The arrows G and H respectively symbolize the entry of the air / powder mixture into part 7 of the diffusion chamber, and its evacuation from part 70, via an outlet conduit 71.

 At the outlet of the device is mounted a connection sleeve provided with a manually operated shutter 21 and an end piece 72 for connection to a hose.

 At the base of part 7 is mounted a shutter 22 intended to purge the diffusion chamber, through a residue evacuation sleeve 73.

 The shutter devices 2, 21 and 22 are of the plug type.

 In operation, the shutters 2 and 21 are open while the shutter 22 is closed.

 The conduit 6 is permanently connected to a source of compressed air supplying pressurized air according to F2.

 When the valve 4 is opened, the powder contained in the tank and in the supply chamber 3 descends into the latter to fall into the transfer duct 5. It is therefore a continuous flow of particles which mixes with the current d air passing through duct 6.

 The air / powder mixture is then diffused in the divergent chamber part 7.

 In this part 7 is a mass of particles in suspension, part of which passes through the holes 80, while the rest abuts against the grid 8 to be taken up by the air flow, until these particles arrive at go through one of the holes 80 in the grid.

 At the outlet of the grid, there is therefore a homogeneous spatial distribution of the particles in the air flow, and it is a regular flow which leaves through the outlet duct 71.

 As already stated, the deflectors limit the packing of the powder in the converging duct 3, while the vibrator 9 promotes the flow of the particles in the narrowed part 30.

 It is possible to stop the arrival of the powder particles by controlling the valve 4 in its closed position. In this case, the air continues to circulate in the duct 6 and in the chamber 7, 70, which makes it possible to eliminate the remaining particles, and to purge the ducts, including in the user apparatus, which is then supplied compressed air only.

 The channel 12, 12 'makes it possible to purge the base of the supply conduit 3 after use.

 Finally, by opening the shutter 22, it is possible to purge the diffusion chamber of all of its residues, normally large particles, incapable of crossing the filtering grid.

 In Figure 2 there is shown an installation using this device 1, symbolically represented by a rectangular outline in broken lines.

 It is an installation for cleaning a surface, for example a building facade, by projection of abrasive particles by means of a projecting head 106. The latter is rotated by a pneumatic motor 105 , via a motion transmission mechanism 300.

 The compressor 100 and the device 1 are normally stationary, while the device 106 is mobile. Its supply of compressed air is therefore through flexible conduits.

 Thus, the rotary head 106 is supplied with an air / powder mixture by the device 1 by means of a flexible pipe 206 connected to the connector 72.

 The device receives compressed air from a compressor 100 via a line 204 connected to the threaded portion 60 of the mixing duct 6.

 On the line 204 is mounted a closing valve 107, which is opened during work.

 The pneumatic motor 105 is also supplied from the compressor 100 by successive flexible pipes 200, 201, 203. On the part 200 is a closing valve 101 and a flow divider 102. Between the parts 201 and 203 is a control valve 103 which is actuated by a small pilot valve 104 the latter is actuated by a trigger (not shown) carried by the device 106, and maneuverable by the operator.

 The actuation of the control valve 103 is done by a compressed air supply duct 202 coming from the divider 102, via the pilot valve 104. The valve 103 is a pneumatically actuated valve normally closed; it changes to the open state when the pilot valve 104 is open.

 Finally, the part 203, located downstream of the control valve 103 is connected respectively by conduits 207 and 208, respectively to the vibrator 9 and to the shut-off valve 4. The conduits 207, 208 and 203 carry throttle valves variable 109, 108, and respectively 110, allowing adjustment of the flow rates.

 For a cleaning operation, the valves 101 and 107 are open and the compressor is started.

 Thus, compressed air arrives in the device, via the pipe 204, the device 1, and the flexible pipe 206.

 As long as the operator does not actuate the trigger, the pilot valve 104 is closed, and does not actuate the control valve 103, which is also consequently closed (positions in FIG. 2).

 When the operator actuates the trigger, he switches the pilot valve 104 to the open position, and compressed air arrives via the pipe 202, at the valve 103. The latter opens and compressed air arrives from the compressor via pipes 200 and 201 in duct 203.

There is then a supply of compressed air to the vibrator 9, which starts to move, to the valve 4 which passes to the open state and to the motor.
105, which rotates the rotary head 106.

 An air / powder mixture distribution is then obtained by the device 1, and the operator cleans the facade, by moving the projection apparatus along the latter.

 When the operator wishes to stop this work, he just has to release the trigger to automatically stop the head rotation drive, stop the vibrator, and stop the powder supply (by closing valve 4). Compressed air continues to be supplied, allowing the pipes and nozzles to be purged.

 As an indication, the narrowed passage section 30 has a diameter between 0.5 and 5 mm, the mixing duct 6 and the outlet duct 71 have a diameter of 12 mm, while the disc 8 has a diameter of 50 mm.

 The pressure of the compressed air supplied by the compressor 100 is between 5 and 10 bars (i.e. 5 x 105 and 106 Pa).

Claims (10)

 1. Device for distributing a mixture of compressed air and very fine-grained powder, characterized in that it comprises, from upstream to downstream in the direction of movement of the powder  a) a powder supply conduit (3), with a substantially frustoconical converging wall, into which the powder flows from a storage tank (C)  b) a valve (4) for closing the outlet orifice (30) of the supply duct (3), capable of selectively occupying an open position or a closed position of said orifice  c) a transfer duct (5)  d) a chamber (6) for mixing the powder with compressed air  e) a diffusion chamber (7, 70) closed by a filtering grid (8) provided with a multitude of holes (80) for passage of small section, slightly greater than the section corresponding to the particle size of the powder  f) an outlet duct (71) for the air / powder mixture.  2. Device according to claim 1, characterized in that said diffusion chamber is composed of two parts (7, 70) coaxial, with frustoconical wall, separated by the filtering grid (8), one (7) divergent, upstream of the grid, and the other (70) converging, downstream of the grid.  3. Device according to claim I or 2, characterized in that said supply duct (3) is substantially vertical, with its outlet orifice (30) directed downwards, and is provided with deflectors (31) limiting the compaction of the powder.  4. Device according to one of claims I to 3, characterized in that it comprises a vibrator (9) disposed in the outlet area of the supply duct (3).  5. Device according to one of claims I to 4, characterized in that said valve (4) and / or said vibrator (9) are pneumatically controlled.  6. Device according to one of claims 1 to 4, characterized in that it consists of a plastic housing (I) containing the various conduits (3, 5, 71) and chambers (6, 7, 70) powder and air passage.  7. Device according to one of claims I to 6, characterized in that it comprises a purge system comprising a channel (12) for supplying compressed air at said outlet orifice (30).  8. Device according to one of claims I to 7, characterized in that there is provided a series of removable and interchangeable tips (32), which have outlet orifices (30) of different fineness, capable of being selectively placed at the base of said supply conduit (3).  9. Device according to one of the preceding claims, characterized in that it is intended to supply an apparatus (106) for spraying abrasive particles for cleaning a surface, this apparatus (106) comprising projection nozzles whose passage section is greater than that of the holes (80) of said filter grid.  10. Device according to claim 9, characterized in that said device (106) is with a rotary head driven by a pneumatic motor (105) and that the control of the latter, the control of said valve (4) and the supply of compressed air from said mixing chamber (6) is from a common source of compressed air, such as a compressor (100).  He. Device according to claim 10, characterized in that it is possible to supply compressed air to the device (106) while said valve (4) is in the closed position.