INSTALLATIONS FOR THE COATING OF PARTS BY POWDERING
United States Patent 3847118
A powdering enclosure shields the parts to be coated and powdering means. A distributing device is situated close to the powdering enclosure and connected to the powdering means. A recovery system treats the gas extracted from the powdering enclosure and an input system introduces into the distributing device a quantity of powder corresponding to a part of that delivered by said distributing device to the abovesaid powdering means. The recovery system comprises a battery of several separating cells traversed by the gas extracted from the powdering enclosure and arranged to retain the powder in suspension in this gas. A first set of valves enables the selective isolation of one at least of these calls. A second set of valves enables the purging of this cell by a neutral gas to clean the cell and to draw the powder in it to a recycling pipe ending at the distributing device. This recycling pipe is traversed by a neutral gas for the pneumatic transport of the powder coming from the cell. The input system comprises a powder reserve communicating with a supply pipe, ending at the distributing device, traversed by a neutral gas for the pneumatic transport of the powder coming from said reserve.
US Patent References:
Apparatus for treating textiles
Smith - July 1950 - 2516349
Electrostatic flocking apparatus
Freeder - June 1959 - 2889805
Parts treating and coating apparatus
Schouw - June 1961 - 2989027
Apparatus for treating textiles
Smith - July 1950 - 2516349
Electrostatic flocking apparatus
Freeder - June 1959 - 2889805
Parts treating and coating apparatus
Schouw - June 1961 - 2989027
Application Number:
05/358955
Publication Date:
11/12/1974
Filing Date:
05/10/1973
View Patent Images:
Export Citation:
Assignee:
Air Industries (Courbevoie, FR)
Primary Class:
Other Classes:
118/629, 118/603, 118/634, 118/610, 118/DIG.007
International Classes:
B05B15/12; G03G11/00
Field of Search:
118/600,602,603,610,612,627,629 117/12R
Primary Examiner:
Reynolds W. C.
Assistant Examiner:
Millstein, Leo
Attorney, Agent or Firm:
Larson, Taylor & Hinds
Claims:
I claim
1. Installation for the coating of parts by powdering, comprising a powdering enclosure shielding the parts to be coated and powdering means, a distributing device situated close to the powdering enclosure and connected to the powdering means, a recovery system adapted to treat the gas extracted from the powdering enclosure and an input system adapted to introduce into the distributing device a quantity of powder corresponding to a part of that delivered by said distributing device to the abovesaid powdering means, in which installation:
2. Installation according to claim 1, arranged to circulate the neutral gas, for creating a non-explosive atmosphere in the isolated separating cell, in the same direction as the carrier gas for the powder which has traversed said cell, so as to avoid any displacement of the powder before the atmosphere of the cell concerned has become non-explosive.
3. Installation according to claim 1, wherein the recycling pipe and the supply pipe each comprise, in front of the distributing device, a separating device adapted to separate the transported powder from the neutral gas passing through said recycling and supply pipes.
4. Installation according to claim 1, comprising means for supplying the powdering enclosure with air, the circulation being effected in open circuit.
5. Installation according to claim 1, comprising means for supplying the powdering enclosure with a neutral gas, and an extraction fan for extracting the neutral gas from the powdering enclosure situated downstream of the battery of separating cells, and means for reintroducing the neutral gas into the powdering enclosure after it has traversed a washing or depowdering device.
6. Installation according to claim 1, including an injection device provided in the linking pipe connecting the powdering enclosure to the plurality of separating cells, and means for supplying said injection device with neutral gas so as to produce in said pipe at least one gaseous jet to isolate said powdering enclosure from the recovery system when conditions indicative of explosion or of combustion are detected in the powdering enclosure.
7. Installation according to claim 6, wherein the connecting pipe comprises, between the injection device and the powdering enclosure, a valve device placing this connecting circuit in communication with the atmosphere when the injection device delivers its gaseous jet.
8. Installation according to claim 1, including means adapted to circulate the same neutral gas through the recycling system, said separating cells and the input system.
9. Installation according to claim 1, adapted to circulate a fuel gas as said neutral gas.
1. Installation for the coating of parts by powdering, comprising a powdering enclosure shielding the parts to be coated and powdering means, a distributing device situated close to the powdering enclosure and connected to the powdering means, a recovery system adapted to treat the gas extracted from the powdering enclosure and an input system adapted to introduce into the distributing device a quantity of powder corresponding to a part of that delivered by said distributing device to the abovesaid powdering means, in which installation:
2. Installation according to claim 1, arranged to circulate the neutral gas, for creating a non-explosive atmosphere in the isolated separating cell, in the same direction as the carrier gas for the powder which has traversed said cell, so as to avoid any displacement of the powder before the atmosphere of the cell concerned has become non-explosive.
3. Installation according to claim 1, wherein the recycling pipe and the supply pipe each comprise, in front of the distributing device, a separating device adapted to separate the transported powder from the neutral gas passing through said recycling and supply pipes.
4. Installation according to claim 1, comprising means for supplying the powdering enclosure with air, the circulation being effected in open circuit.
5. Installation according to claim 1, comprising means for supplying the powdering enclosure with a neutral gas, and an extraction fan for extracting the neutral gas from the powdering enclosure situated downstream of the battery of separating cells, and means for reintroducing the neutral gas into the powdering enclosure after it has traversed a washing or depowdering device.
6. Installation according to claim 1, including an injection device provided in the linking pipe connecting the powdering enclosure to the plurality of separating cells, and means for supplying said injection device with neutral gas so as to produce in said pipe at least one gaseous jet to isolate said powdering enclosure from the recovery system when conditions indicative of explosion or of combustion are detected in the powdering enclosure.
7. Installation according to claim 6, wherein the connecting pipe comprises, between the injection device and the powdering enclosure, a valve device placing this connecting circuit in communication with the atmosphere when the injection device delivers its gaseous jet.
8. Installation according to claim 1, including means adapted to circulate the same neutral gas through the recycling system, said separating cells and the input system.
9. Installation according to claim 1, adapted to circulate a fuel gas as said neutral gas.
Description:
The invention relates to installations for the coating of parts by powdering, the parts thus coated with a layer of powder of given thickness being then subjected to a suitable treatment to fix this powder and to obtain an adherent protective coating.
In such installations, the powder is distributed into a powdering enclosure by powdering means generally constituted by one or several electrostatic installations spraying the powder, electrified in its passage through said installations, on to the part which is then brought to an electrical potential different from that to which the powder is brought.
These powdering installations are connected to a distributing device situated close to the powdering enclosure, and they deliver a flow-rate of powder greater than that necessary for the coating.
The atmosphere of the powdering enclosure is constantly renewed by blower means and the gas extracted from said powdering enclosure is directed towards a recovery circuit where all or part of the powder contained in this gas is recovered.
Moreover, the installation comprises an input system enabling the introduction into the distributing device of an amount of powder corresponding to a part of that delivered by said distributing device to the powdering apparatus.
It is an object of the invention to improve installations of the aforementioned type, especially as regards the arrangement of the recovery circuit and of the input circuit.
The invention has a further object of improving these installations especially as regards the elimination of the risks of explosion and of fire in the distributing device, in the recovery system, in the input system and in the powdering enclosure proper.
The invention is applicable more particularly to installations intended for the automobile industry, the parts on which it is desired to obtain a protective coating being automobile bodies.
The installation according to the invention comprises a powdering enclosure shielding the parts to be coated and the powdering apparatuses, a distributing device being situated close to the powdering enclosure and connected to the powdering apparatuses, a recovery circuit treating the gases extracted from the powdering enclosure, and an input circuit introducing into the distributing device a quantity of powder corresponding to a part of that delivered by the said distributing device to the abovesaid powdering apparatuses, and this installation is characterised by the fact that,
the recovery system comprises a battery of several separating cells traversed by the gas extracted from the powdering enclosure and arranged to retain the powder in suspension in this gas, a first set of valves enabling the selective isolation of one at least of these cells, a second set of valves enabling the injection into the cell thus isolated of a neutral gas for purging this cell of the gas contained in it, which can be a fuel, to complete the clearance and cleaning of this cell and to draw the powder retained in it cell towards a recycling pipe ending at the distributing device, this recycling pipe being traversed by a neutral gas ensuring the pneumatic transport of the powder coming from the abovesaid cell,
and the input system comprises a reserve of powder communicating with a supply pipe ending at the distributing device, this supply pipe being traversed by a neutral gas providing for the pneumatic transportation of the powder coming from the abovesaid reserve.
It will then be seen that it is possible to arrange the powder reserve relatively far from the powdering enclosure, and, especially to render this powder reserve accessible to delivery vehicles or containers (lorries or special wagons equipped for the transportation of pulverulent materials).
Moreover, the presence of a neutral gas ensuring the entraining and transportation of the powder enables the elimination of explosion risks in the distributing device, in the recovery system, in the input system and in the powdering enclosure proper.
According to an advantageous feature of the invention, the neutral gas, for creating a non-explosive atmosphere in the isolated separation cell, circulates in the same direction as the powder carrier gas which has passed through this cell, this in order to avoid any movement of the powder before the atmosphere of the cell concerned has become non-explosive.
According to yet another advantageous feature of the invention, the recycling pipe and the supply pipe each comprise, in front of the distributing device, a separating device in which the powder transported is separated from the neutral gas passing through the abovesaid recycling and supply pipes.
The invention consists, apart from the features which have just been considered, of certain other features which are preferably used at the same time and which will be more explicitly considered below.
The invention will in any case be well understood by means of the additional description which follows as well as of the accompanying drawing, which description and drawing relate to a preferred embodiment of the invention, and do not comprise of course any limiting nature.
The single FIGURE of this drawing is a diagrammatic view of a powdering installation constructed according to the invention.
This installation comprises a powdering enclosure 1, in which the parts to be coated 2, such as automobile bodies, are borne by a conveyor 3.
The powder is distributed into this powdering enclosure 1 by a powdering apparatus 4 which can be constituted by several electrostatic guns 4a, 4b, 4c and 4d spraying the powder, electrified on its passage through said guns, on to the part 2 which is then brought to a potential different from that to which the powder is brought.
These powdering apparatuses 4 are connected to a distributing device 5 situated close to the powdering enclosure 1.
The powdering enclosure 1 is supplied with clean gas through a blower fan 6 introducing this clean gas into the said enclosure, preferably through its ceiling. Below the floor of the powdering enclosure 1 there are provided one or several hoppers 7 through which the gas is extracted from the powdering enclosure 1, this gas containing in suspension a certain amount of powder since the powdering apparatuses 4 deliver a flow-rate of powder greater than that necessary for coating the parts 2. By way of example, and within the field of application of coatings to automobile bodies, it may be indicated that a high proportion (of the order of 40 percent) of the flow-rate of powder delivered by the powdering apparatuses occurs in the gas extracted from the powdering enclosure.
Under these conditions, there is provided a recovery system, denoted in a general way by the reference numeral 8, to treat the gas extracted from the powdering enclosure 1.
As for the distributing device 5, it cooperates with an input system, denoted in a general way by the reference numeral 9, this input system 9 introducing into the distributing device 5 an amount of powder corresponding to a part of that delivered by a said distributing device 5 to the powdering apparatuses 4.
The recovery system 8 comprises a battery of several separating cells 10a, 10b, 10c traversed by the gas extracted from the powdering enclosure, and arranged to retain the powder in suspension in this gas.
The first set of valves 11a, 11b, 11c enables the isolation selectively at one at least of the cells 10a, 10b and 10c and a second set of valves 12a, 12b, and 12c enables the injection into the cell thus isolated of a neutral gas for purging this cell of the gas that it contained and which can be a fuel, to complete the clearing and cleaning of this cell, and to entrain the powder retained in this cell to a recycling pipe 13 ending at the distributing device 5, this recirculating pipe 13 being traversed by a neutral gas ensuring the pneumatic transport of the powder coming from the abovesaid cell.
The neutral gas, intending to create a non-explosive atmosphere in the isolated separating cell, flows in the same direction as the carrier gas for the powder which has traversed this cell, this in order to avoid any movement of the powder before the atmosphere of the cell concerned has become non-explosive.
The input system 9 comprises a reserve of powder 14 communicating with a supply pipe 15 ending at the distributing device 5, this supply pipe 15 being traversed by a neutral gas ensuring pneumatic transport coming from this reserve 14.
The separating cells 10a, 10b, 10c are provided respectively, at their lower part, with isolating valves 16a, 16b, 16c ending in a hopper 17 the powder coming from these cells being directed by gravity towards the recycling pipe 13 through a valve 18.
The powder is introduced into this recycling pipe 13 through a blower device 19 in which the neutral gas mixes with the powder to thereby ensure the pneumatic transport.
The powder coming from the reserve 14 is directed by gravity towards the supply pipe 15 through a rotary valve 20.
The powder is introduced into this supply pipe 15 through a blower device 21 in which the neutral gas is mixed with the powder to ensure the pneumatic transport thereof.
The neutral gas used is the same in the recovery circuit 8 and in the input circuit 9 and nitrogen can advantageously be used.
A bottle of compressed nitrogen 22 is therefore arranged to supply, on one hand, the recovery system 8, through a valve 23, and on the other hand, the battery of separating cells 10a, 10b, 10c, through a set of valves 12a, 12b, 12c. In the recycling pipe 13 the neutral gas is placed in circulation by a fan 24 or a compressor of the "ROOTS" type, followed by a cooler 25.
For ease of installation there may be enclosure; another bottle of compressed nitrogen 26 to feed the supply system 9, through a valve 27.
One of these two bottles of compressed nitrogen, for example the bottle 26, can also feed for their pressurisation, the reserve 14, the distributing device 5, and a vehicle or a delivery container 28. One or several valves such as 29 can then be provided to control these different functions. In the supply pipe 15 the neutral gas is placed in circulation through a blower 30 or a compressor of the "ROOTS" type, followed by a cooler 31.
The recycling pipe 13 and the supply pipe 15 each comprise, in front of the distributing device 5, a separating device, respectively 32 and 33, in which the transported powder is separated from the neutral gas by passing through the abovesaid recycling 13 and supply 15 pipes.
The separating device 32 communicates with a hopper 34, situated in the distributing device 5, through a valve 35, and the separating device 33 communicates with a hopper 36, located in the distributing device 5, through a valve 37.
The distributing device 5 is also provided with a third hopper 38 in which there may be introduced, through a valve 39, supplementary substances (dyes, consumable additives, etc.).
Downstream of the battery of separating cells 10a, 10b, 10c there are provided an extraction fan 40 connected to the abovesaid cells by a set of valves 41a, 41b, 41c.
The powdering enclosure 1 being supplied with air, the circulation of air is effected in open circuit, and the air recycling through the extraction fan 40 is ejected to the atmosphere, if necessary after having been washed to eliminate the particules of residual powder.
If the powdering enclosure 1 is supplied with neutral gas, the circulation of this neutral gas is effected in closed circuit, and the gas recycled by the extraction fan 40 is brought back to the blower fan 6 through a return circuit 42 (shown in mixed line), in which a washing device or powder remover 43 is arranged to remove the particles of residual powder.
The powdering enclosure 1 is generally provided with an upstream ante-chamber 44 and a downstream ante-chamber 45, the gas extracted from these two chambers 44 and 45 being discarded to the atmosphere, if necessary after having traversed a washing or powder removing device 46 to eliminate the particles of powder which have accidentally passed from the powdering enclosure to one and/or other of these two chambers.
In the linking pipe 47 connecting the hopper 7 of the powdering enclosure 1 to the battery of separating cells 10a, 10b, 10c, there is provided advantageously an injector device 48 through which neutral gas can be introduced into the pipe 47 in the form of two opposed jets. This introduction is actuated by an electrovalve 49 connected to one or several fire detectors 50 arranged in the powdering enclosure 1.
Due to this arrangement, and when a shock wave (due to an explosion) or a light or infra-red radiation (due to slow combustion) is detected by the one or more detectors 50 and the powdering enclosure 1, the electrovalve 49 opens and a neutral buffer gas is admitted into the pipe 47 between the powdering enclosure 1 and the recovery system 8 comprising the battery of separating cells 10a, 10b, 10c.
The spreading of the fire to this battery is hence avoided, taking into account the amount of powder retained in the cells, which combines with the air, the necessary components for an explosive reaction.
Moreover, the rapid admission of neutral gas into the pipe 47 can be put to profit to actuate a valve device 51 placing this passage in communication with the atmosphere and avoiding hot gases or even flames, from being aspirated to the extraction fan 40 and spreading the fire to the battery of separating cells 10a, 10b, 10c.
Finally and whatever the embodiment adopted, there is provided an installation which has a certain number of advantages among which may be mentioned those summarised by the following points:
possibility of arranging the reserve of powder at a relatively distant point from the powdering enclosure, which enables this reserve powder to be rendered accessible to vehicles and delivery containers, this advantage being particularly important when the consumption of powder is high, which is the case in installations intended for the automobile industry;
considerable reduction in the risks of explosion and fire in the distributing device, in the recovery system and in the input system, and this by reason of the neutral gas which flows in these parts of the installation and which creates an inert atmosphere on clearing and cleaning of the separating cells (the most dangerous operation which occurs during the functioning of the installation);
the possibility of ventilating the powdering enclosure with a neutral gas, circulating in the closed circuit, which considerably reduces the risk of explosion and fire in the powdering enclosure ;
the detection of explosions and of fires in the powdering enclosure and immediate isolation of the recovery system with respect to the powdering enclosure.
As is self evident, and as emerges already from the foregoing; the invention is in no way limited to those of its types of application and embodiments which have been more especially envisaged; it encompasses, on the contrary, all modifications.
In such installations, the powder is distributed into a powdering enclosure by powdering means generally constituted by one or several electrostatic installations spraying the powder, electrified in its passage through said installations, on to the part which is then brought to an electrical potential different from that to which the powder is brought.
These powdering installations are connected to a distributing device situated close to the powdering enclosure, and they deliver a flow-rate of powder greater than that necessary for the coating.
The atmosphere of the powdering enclosure is constantly renewed by blower means and the gas extracted from said powdering enclosure is directed towards a recovery circuit where all or part of the powder contained in this gas is recovered.
Moreover, the installation comprises an input system enabling the introduction into the distributing device of an amount of powder corresponding to a part of that delivered by said distributing device to the powdering apparatus.
It is an object of the invention to improve installations of the aforementioned type, especially as regards the arrangement of the recovery circuit and of the input circuit.
The invention has a further object of improving these installations especially as regards the elimination of the risks of explosion and of fire in the distributing device, in the recovery system, in the input system and in the powdering enclosure proper.
The invention is applicable more particularly to installations intended for the automobile industry, the parts on which it is desired to obtain a protective coating being automobile bodies.
The installation according to the invention comprises a powdering enclosure shielding the parts to be coated and the powdering apparatuses, a distributing device being situated close to the powdering enclosure and connected to the powdering apparatuses, a recovery circuit treating the gases extracted from the powdering enclosure, and an input circuit introducing into the distributing device a quantity of powder corresponding to a part of that delivered by the said distributing device to the abovesaid powdering apparatuses, and this installation is characterised by the fact that,
the recovery system comprises a battery of several separating cells traversed by the gas extracted from the powdering enclosure and arranged to retain the powder in suspension in this gas, a first set of valves enabling the selective isolation of one at least of these cells, a second set of valves enabling the injection into the cell thus isolated of a neutral gas for purging this cell of the gas contained in it, which can be a fuel, to complete the clearance and cleaning of this cell and to draw the powder retained in it cell towards a recycling pipe ending at the distributing device, this recycling pipe being traversed by a neutral gas ensuring the pneumatic transport of the powder coming from the abovesaid cell,
and the input system comprises a reserve of powder communicating with a supply pipe ending at the distributing device, this supply pipe being traversed by a neutral gas providing for the pneumatic transportation of the powder coming from the abovesaid reserve.
It will then be seen that it is possible to arrange the powder reserve relatively far from the powdering enclosure, and, especially to render this powder reserve accessible to delivery vehicles or containers (lorries or special wagons equipped for the transportation of pulverulent materials).
Moreover, the presence of a neutral gas ensuring the entraining and transportation of the powder enables the elimination of explosion risks in the distributing device, in the recovery system, in the input system and in the powdering enclosure proper.
According to an advantageous feature of the invention, the neutral gas, for creating a non-explosive atmosphere in the isolated separation cell, circulates in the same direction as the powder carrier gas which has passed through this cell, this in order to avoid any movement of the powder before the atmosphere of the cell concerned has become non-explosive.
According to yet another advantageous feature of the invention, the recycling pipe and the supply pipe each comprise, in front of the distributing device, a separating device in which the powder transported is separated from the neutral gas passing through the abovesaid recycling and supply pipes.
The invention consists, apart from the features which have just been considered, of certain other features which are preferably used at the same time and which will be more explicitly considered below.
The invention will in any case be well understood by means of the additional description which follows as well as of the accompanying drawing, which description and drawing relate to a preferred embodiment of the invention, and do not comprise of course any limiting nature.
The single FIGURE of this drawing is a diagrammatic view of a powdering installation constructed according to the invention.
This installation comprises a powdering enclosure 1, in which the parts to be coated 2, such as automobile bodies, are borne by a conveyor 3.
The powder is distributed into this powdering enclosure 1 by a powdering apparatus 4 which can be constituted by several electrostatic guns 4a, 4b, 4c and 4d spraying the powder, electrified on its passage through said guns, on to the part 2 which is then brought to a potential different from that to which the powder is brought.
These powdering apparatuses 4 are connected to a distributing device 5 situated close to the powdering enclosure 1.
The powdering enclosure 1 is supplied with clean gas through a blower fan 6 introducing this clean gas into the said enclosure, preferably through its ceiling. Below the floor of the powdering enclosure 1 there are provided one or several hoppers 7 through which the gas is extracted from the powdering enclosure 1, this gas containing in suspension a certain amount of powder since the powdering apparatuses 4 deliver a flow-rate of powder greater than that necessary for coating the parts 2. By way of example, and within the field of application of coatings to automobile bodies, it may be indicated that a high proportion (of the order of 40 percent) of the flow-rate of powder delivered by the powdering apparatuses occurs in the gas extracted from the powdering enclosure.
Under these conditions, there is provided a recovery system, denoted in a general way by the reference numeral 8, to treat the gas extracted from the powdering enclosure 1.
As for the distributing device 5, it cooperates with an input system, denoted in a general way by the reference numeral 9, this input system 9 introducing into the distributing device 5 an amount of powder corresponding to a part of that delivered by a said distributing device 5 to the powdering apparatuses 4.
The recovery system 8 comprises a battery of several separating cells 10a, 10b, 10c traversed by the gas extracted from the powdering enclosure, and arranged to retain the powder in suspension in this gas.
The first set of valves 11a, 11b, 11c enables the isolation selectively at one at least of the cells 10a, 10b and 10c and a second set of valves 12a, 12b, and 12c enables the injection into the cell thus isolated of a neutral gas for purging this cell of the gas that it contained and which can be a fuel, to complete the clearing and cleaning of this cell, and to entrain the powder retained in this cell to a recycling pipe 13 ending at the distributing device 5, this recirculating pipe 13 being traversed by a neutral gas ensuring the pneumatic transport of the powder coming from the abovesaid cell.
The neutral gas, intending to create a non-explosive atmosphere in the isolated separating cell, flows in the same direction as the carrier gas for the powder which has traversed this cell, this in order to avoid any movement of the powder before the atmosphere of the cell concerned has become non-explosive.
The input system 9 comprises a reserve of powder 14 communicating with a supply pipe 15 ending at the distributing device 5, this supply pipe 15 being traversed by a neutral gas ensuring pneumatic transport coming from this reserve 14.
The separating cells 10a, 10b, 10c are provided respectively, at their lower part, with isolating valves 16a, 16b, 16c ending in a hopper 17 the powder coming from these cells being directed by gravity towards the recycling pipe 13 through a valve 18.
The powder is introduced into this recycling pipe 13 through a blower device 19 in which the neutral gas mixes with the powder to thereby ensure the pneumatic transport.
The powder coming from the reserve 14 is directed by gravity towards the supply pipe 15 through a rotary valve 20.
The powder is introduced into this supply pipe 15 through a blower device 21 in which the neutral gas is mixed with the powder to ensure the pneumatic transport thereof.
The neutral gas used is the same in the recovery circuit 8 and in the input circuit 9 and nitrogen can advantageously be used.
A bottle of compressed nitrogen 22 is therefore arranged to supply, on one hand, the recovery system 8, through a valve 23, and on the other hand, the battery of separating cells 10a, 10b, 10c, through a set of valves 12a, 12b, 12c. In the recycling pipe 13 the neutral gas is placed in circulation by a fan 24 or a compressor of the "ROOTS" type, followed by a cooler 25.
For ease of installation there may be enclosure; another bottle of compressed nitrogen 26 to feed the supply system 9, through a valve 27.
One of these two bottles of compressed nitrogen, for example the bottle 26, can also feed for their pressurisation, the reserve 14, the distributing device 5, and a vehicle or a delivery container 28. One or several valves such as 29 can then be provided to control these different functions. In the supply pipe 15 the neutral gas is placed in circulation through a blower 30 or a compressor of the "ROOTS" type, followed by a cooler 31.
The recycling pipe 13 and the supply pipe 15 each comprise, in front of the distributing device 5, a separating device, respectively 32 and 33, in which the transported powder is separated from the neutral gas by passing through the abovesaid recycling 13 and supply 15 pipes.
The separating device 32 communicates with a hopper 34, situated in the distributing device 5, through a valve 35, and the separating device 33 communicates with a hopper 36, located in the distributing device 5, through a valve 37.
The distributing device 5 is also provided with a third hopper 38 in which there may be introduced, through a valve 39, supplementary substances (dyes, consumable additives, etc.).
Downstream of the battery of separating cells 10a, 10b, 10c there are provided an extraction fan 40 connected to the abovesaid cells by a set of valves 41a, 41b, 41c.
The powdering enclosure 1 being supplied with air, the circulation of air is effected in open circuit, and the air recycling through the extraction fan 40 is ejected to the atmosphere, if necessary after having been washed to eliminate the particules of residual powder.
If the powdering enclosure 1 is supplied with neutral gas, the circulation of this neutral gas is effected in closed circuit, and the gas recycled by the extraction fan 40 is brought back to the blower fan 6 through a return circuit 42 (shown in mixed line), in which a washing device or powder remover 43 is arranged to remove the particles of residual powder.
The powdering enclosure 1 is generally provided with an upstream ante-chamber 44 and a downstream ante-chamber 45, the gas extracted from these two chambers 44 and 45 being discarded to the atmosphere, if necessary after having traversed a washing or powder removing device 46 to eliminate the particles of powder which have accidentally passed from the powdering enclosure to one and/or other of these two chambers.
In the linking pipe 47 connecting the hopper 7 of the powdering enclosure 1 to the battery of separating cells 10a, 10b, 10c, there is provided advantageously an injector device 48 through which neutral gas can be introduced into the pipe 47 in the form of two opposed jets. This introduction is actuated by an electrovalve 49 connected to one or several fire detectors 50 arranged in the powdering enclosure 1.
Due to this arrangement, and when a shock wave (due to an explosion) or a light or infra-red radiation (due to slow combustion) is detected by the one or more detectors 50 and the powdering enclosure 1, the electrovalve 49 opens and a neutral buffer gas is admitted into the pipe 47 between the powdering enclosure 1 and the recovery system 8 comprising the battery of separating cells 10a, 10b, 10c.
The spreading of the fire to this battery is hence avoided, taking into account the amount of powder retained in the cells, which combines with the air, the necessary components for an explosive reaction.
Moreover, the rapid admission of neutral gas into the pipe 47 can be put to profit to actuate a valve device 51 placing this passage in communication with the atmosphere and avoiding hot gases or even flames, from being aspirated to the extraction fan 40 and spreading the fire to the battery of separating cells 10a, 10b, 10c.
Finally and whatever the embodiment adopted, there is provided an installation which has a certain number of advantages among which may be mentioned those summarised by the following points:
possibility of arranging the reserve of powder at a relatively distant point from the powdering enclosure, which enables this reserve powder to be rendered accessible to vehicles and delivery containers, this advantage being particularly important when the consumption of powder is high, which is the case in installations intended for the automobile industry;
considerable reduction in the risks of explosion and fire in the distributing device, in the recovery system and in the input system, and this by reason of the neutral gas which flows in these parts of the installation and which creates an inert atmosphere on clearing and cleaning of the separating cells (the most dangerous operation which occurs during the functioning of the installation);
the possibility of ventilating the powdering enclosure with a neutral gas, circulating in the closed circuit, which considerably reduces the risk of explosion and fire in the powdering enclosure ;
the detection of explosions and of fires in the powdering enclosure and immediate isolation of the recovery system with respect to the powdering enclosure.
As is self evident, and as emerges already from the foregoing; the invention is in no way limited to those of its types of application and embodiments which have been more especially envisaged; it encompasses, on the contrary, all modifications.