JP3429316B2 - Vehicle powder coating system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This is described in US patent application Ser. No. 08 / 066,873 to Shutic et al., Filed May 25, 1993, entitled Vehicle Powder Coating System and owned by the assignee of the present invention. It is a partial continuation application.

FIELD OF THE INVENTION The present invention relates to powder coating systems, and more particularly to powder spray booths, powder collection and recovery systems, and mixtures of fresh powder coating materials with fresh and recycled or oversprayed powder coating materials. The present invention relates to a powder coating system for use in a vehicle manufacturing facility including a powder supply device that conveys powder from a distant position to a coating dispenser attached to a spray booth.

BACKGROUND OF THE INVENTION The task of applying coating materials to large objects such as automobiles and other bodywork has traditionally been done at the entrance of the bodywork, the paint application area, and depending on the design, the curing or drying area, and the exit of the bodywork. It has been implemented in a spray booth with an elongated tunnel-like structure. Many systems introduce "conditioned" air, that is, humidified and filtered air, into a plenum chamber at the top of a booth with a blower or blower fan, and then direct it to vehicles passing through the booth. To orient downward. The conditioned air picks up the overspray coating material in the booth chamber and the airborne overspray material is exhausted downwardly by one or more exhaust fans through the floor or sides of the booth. A filter is provided to capture excess sprayed paint material and the resulting filtered or clean air is drawn from the booth,
Exhaust to atmosphere or recirculate in system for reuse.

The most commonly used coating material for vehicles such as automobiles and trucks is a high-solid resin coating material having a relatively high proportion of a liquid solvent component that facilitates atomization of the resin material. The problems associated with the recovery of oversprayed resin coating materials are well documented and continue to be an environmental issue in the coating and finishing industry. See U.S. Pat. No. 4,247,591 to Cobbs and 4,553,701 to Rehman et al.

Powder coating materials are an alternative to solvent-based liquid coating materials for coating large objects such as car bodies, as disclosed in US Pat.No. 5,078,084, attributed to Shutic et al. And owned by the assignee of the present invention. Has been proposed. In the practice of powder coating, when the powdered resin is applied to the substrate and then the substrate and the powder are heated, the powder is melted and then cooled,
Form a continuous solid film on the substrate. In most powder spraying applications, the amount of powder adhering to the substrate increases and imparts an electrostatic charge to the spraying powder towards a grounded object to be applied to help hold the powder on the substrate. The operation of applying powder material to the body of an automobile or truck is carried out in a spray booth that provides a controlled area where excess spray powder that does not adhere to the car body can be collected. The containment of excess sprayed powder in the booth is assisted by an exhaust system that creates a negative pressure in the booth chamber to draw excess sprayed powder out of the booth and into the powder collection and recovery system. The recovered overspray powder can be stored for future use or immediately recycled to a powder spray gun associated with the powder spray booth.

There are some inherent problems in coating automobiles and other bodywork with powder coating materials. Due to the design of vehicle manufacturing facilities, the source of coating material is typically located far away from the spray booth, or hundreds of feet. In addition, large quantities of powder coating material, such as over 136.2 kilograms (300 pounds) per hour, can be used at 0.454 to 0.9 per second.
This relatively long distance must be transferred from the source to the spray booth at a rate such as 08 kilograms (1-2 pounds). Further, in order to properly coat the powder material on the vehicle body, the powder coating material must be transferred with an appropriate density and particle distribution. The term "density" refers to the relative mixing or proportion of powder and air, and "particle distribution"
The term refers to a distribution of powder particles of various sizes in a stream of air-borne powder material that is sent to a spray gun associated with a powder spray booth. It has been found that currently available powder coating systems are unable or unable to maintain the desired density and particle distribution while transferring large amounts of powder material over large distances at high flow rates. .

As described above, not all of the powder coating material released in the powder spray booth adheres to the vehicle body passing through the booth. This oversprayed powder material is collected in a powder collection and recovery system at the base of a booth, such as disclosed in US Pat. No. 5,078,084 to Shutic et al. In this type of system, the powder collection and collection system includes individual groups or banks of cartridge filters that are individually contained in a series of powder collection chambers mounted side by side under the floor of the spray booth. A single exhaust fan or blower creates a negative pressure in the booth chamber, which sucks excess blown airborne powder material into the individual powder collection chambers where the powder is Collected on the walls of the cartridge filter, "clean air" passes through it and is then released to the atmosphere. By manipulating the reverse air jet to remove the collected powder from the walls of the cartridge filter, the powder falls to the base of the powder collection chamber where it is sprayed with the spray gun associated with the powder spray booth. Ejected for collection or recycling for return to the gun.

In a large number of applications, such as painting the body of an automobile, the practicality of the powder collection and recovery system and the application of uniform negative pressure in the booth compartment are particularly problematic. Obtaining a uniform negative pressure in the booth room using a single exhaust fan or blower fan can be somewhat difficult in some cases, which adversely affects the efficiency with which the powder coating material can be collected, and It has been found that it can disrupt the pattern of powder coating material emitted from the spray gun on the passing vehicle body. In this type of system, there is also a need to improve the utility of the reverse air jet valve contained within each powder recovery chamber.

Another problem with powder coating systems of the type described above is with respect to recovery of excess spray powder for recirculation back to the spray gun associated with the powder spray booth. . The unused powder coating material is
It includes powder particles with a wide range of particle size distribution, that is, a wide variety of sizes. Larger powder particles tend to adhere to objects to be coated in the spray booth. Because of their size, they have a higher electrostatic charge than the smaller particles, and the larger, heavier particles have a larger moment when ejected from the spray gun towards the painted object. . As a result, the powder that is over-sprayed and collected to recirculate back to the spray gun without sticking to the object has a higher percentage of particles than the unused powder. This is because larger particles have a higher rate of adhering to an object than smaller particles.

The stability of operation of powder coating systems depends, at least in part, on how to avoid the deposition or accumulation of "fines", eg, particles having a size of less than about 10 microns. The term "stability" as used herein refers to the ability of the system to fluidize, transfer and spray powder coating materials without the problems caused by excessive levels of fines. The presence of excessive levels of fines in the powder coating material results in poor powder fluidization, impingement fusion, clogging of filter cartridges and sieves, powder on the inside of the powder spray booth and on the spray gun. May result in increased adhesion and reduced coating efficiency. The term "impingement fusion" refers to the adhesion of powder particles to a surface as a result of particle velocity due to electrostatic attraction, and "coating efficiency" refers to the amount of powder sprayed onto an object relative to the object. It is a measure of the percentage of powder material that has adhered.

Powder coating systems of the type described above include measures to ensure system stability when re-circulating oversprayed powder material to the spray gun after collection.
Basically not. Ventilation units are used to remove fines from feed hoppers, etc., but such units have limited effectiveness and control the level or percentage of fines in a given feed hopper with the desired accuracy. You can't rely on it, though.

SUMMARY OF THE INVENTION Therefore, it is possible to convey a large amount of powder material over a long distance at a relatively large flow rate while maintaining a desired density and particle distribution, and to obtain an appropriate amount of powder coating material in a system regardless of the required amount. , And collect and recover large amounts of oversprayed powder efficiently for recirculation, avoiding buildup of excessive levels of fines, and relatively easy maintenance for automobiles and other vehicle bodies. It is part of the object of the present invention to provide a powder spray system for applying powder coating material to large objects such as.

These purposes are for applying powder coating materials to large objects such as cars, trucks or other car bodies,
The powder spray booth that defines the control area where the powder coating material is applied to the vehicle body, the "powder kitchen" located far from the powder spray booth, and the powder spray booth located near the booth. It is accomplished in an apparatus that includes several feed hoppers that receive powder coating material from a body kitchen and supply it to a booth associated powder spray gun that is either automatically or manually operated. The over-sprayed powder coating material is removed from the booth room by a powder collection and recovery system, which then recycles the over-sprayed powder to a powder spray gun in the powder kitchen. Return to one or more of the mixing hoppers.

One aspect of the present invention is based on the concept of providing an effective means for transferring powder coating material from a distant or powder kitchen location to a feed hopper located near a spray booth. is expected. This is accomplished in the device of the present invention by a powder transfer system operating at vacuum or negative pressure rather than positive pressure. The powder kitchen includes one or more primary hoppers, each coupled to a powder receiving unit, connected to a source of fresh powder coating material within the powder kitchen. The transfer line interconnects the primary hopper with a powder receiving unit associated with each supply hopper of the spray booth. The first vacuum pump is operated to generate a negative pressure in the powder receiving unit associated with the primary hopper, sucking unused powder material from the supply source into the powder receiving unit to transfer the powder to the primary Can be supplied to the hopper. A second vacuum pump provides a negative pressure within each powder receiving unit associated with the feed hopper,
Thus, unused powder material from the primary hopper located in the powder kitchen is sucked through the long transfer line into the powder receiving unit associated with the supply hopper near the spray booth. The powder receiving unit in the spray booth fills the individual supply hoppers with powder and the powder pump transfers the powder from the supply hopper to the powder spray gun in the spray booth.

This same principle of negative pressure applied powder transfer is used to collect excess spray powder material from the spray booth. A regeneration hopper located within the powder kitchen is coupled to a powder receiving unit, which is connected by a regeneration line to a powder collection and recovery system associated with the powder spray booth. The vacuum pump creates a negative pressure in the powder receiving unit associated with the reclaim hopper that receives the oversprayed powder from the booth and transfers such oversprayed powder to the recycle hopper. In one preferred embodiment of the present invention, the regenerated oversprayed powder is
Next, the powder is conveyed from the regeneration hopper at a negative pressure by another vacuum pump, and the excess sprayed powder is supplied to the powder receiving unit connected to the supply hopper located near the booth. next,
The feed hopper feeds excess spray powder to a spray gun associated with the spray booth, which operates to apply the powder to other parts of the vehicle body to be painted.

In another embodiment, the regeneration hopper and the primary hopper are each connected to a mixing hopper located within the powder kitchen. Powder pumps in the primary and recycle hoppers transfer a selected proportion of virgin powder and regenerated or oversprayed powder to a mixing hopper, where such powders are:
It is mixed here in preparation for transfer to the spray gun associated with the spray booth. According to the method of the present invention, in which the particle size distribution of the powder contained in the mixing hopper is mathematically expected, according to the method of the present invention, the supply of virgin powder and regenerated powder introduced into the mixing hopper is contained in the mixing hopper. The volume percentage of fines is controlled so that it does not exceed a predetermined maximum percentage. This ensures a stable operation of the powder coating system when applying regenerated or oversprayed powder to objects in the booth.

For example, a large amount of powder coating material of about 136.2 kilograms (300 pounds) or more per hour can be efficiently and effectively conveyed by the above-mentioned vacuum transfer system, and the source of the powder coating material is a powder spray booth. Has been found to meet the specific needs of distantly located automobile manufacturing facilities. The use of negative pressure rather than positive pressure is believed to result in lower air usage and therefore lower overall system energy requirements. Also, if any one of the transfer lines extending between the powder kitchen and the spray booth leaks, the powder material will be forced out to the outside in the case of a positive pressure powder transfer system. In such transfer lines, a vacuum is drawn inside the line. This reduces the risk of powder contamination of the facility should a leak problem occur.

Another feature of the powder transfer aspect of the present invention relates to automatically monitoring and replenishing unused powder coating material and oversprayed powder material as the coating operation proceeds.
Each of the primary hopper, recycle hopper and feed hopper is carried by a load cell connected to a programmable logic controller. This load cell is effective for weighing the weight of powder material into each individual hopper during system operation, with the individual hoppers set to zero reference with empty weight. For example, considering a primary hopper, its associated load cell sends a signal to the controller during operation of the system that indicates the weight of the powder in such a primary hopper. When the amount of powder material in the primary hopper falls below a predetermined minimum value, the controller receives a signal from the load cell and connects to the powder receiving unit associated with such a primary hopper. The vacuum pump is activated so that additional virgin powder coating material is transported from the source to the powder receiving unit and then to the primary hopper. When the primary hopper receives a sufficient level of powder coating material, further powder supply is stopped. Regeneration hoppers and feed hoppers operate in a similar manner so that during powder coating operations each maintains an appropriate level of powder coating material. In one embodiment, a connection line is provided between each of the primary hopper and the recycle hopper so that the amount of excess spray powder material collected by the powder collection and recovery system of the spray booth is within the recycle hopper. Unused powder coating material can be fed from the primary hopper to the recycle hopper if the amount of powder material is insufficient to maintain the desired level.

In another embodiment, a programmable controller includes a transfer of unused powder coating material from each primary hopper and associated hoppers in accordance with a selection rate determined by the method described above and discussed in detail below. Control over regeneration or transfer of oversprayed powder from the mixing hopper to the mixing hopper. The mixing hopper mixes the mixture of unused powder and regenerated powder with 1
Supply more than one spray gun.

Another aspect of the invention is that the structure of each of the primary hopper, recycle hopper and feed hopper ensures that the powder coating material is transported through the system at the desired density and particle distribution and is fed to the spray gun. Regarding measures.
In this aspect, similar operating principles to those used in the powder feed hoppers disclosed in U.S. Pat. It is used. Generally, each hopper herein includes a perforated plate that receives an upward flow of air through a baffle located in the base space of such a hopper. An agitator containing a rotating paddle or blade is placed over the perforated plate to ensure proper fluidization of the powder material, even distribution of the powder particles, and proper distribution prior to discharge from the individual hoppers. Different densities or air to particle ratios are ensured.

Yet another aspect of the present invention provides a powder spray booth with an efficient and easily maintainable powder collection and recovery system,
This is based on the concept of creating a homogeneous, downward air flow in the booth chamber. The powder collection and recovery system is modular in construction and includes several powder collection units mounted side-by-side under the floor along the length of the powder spray booth. Each powder collection unit includes a powder collection chamber, which is in two groups or two rows mounted in an inverted V shape on an angled fluidizing plate located at the base of the powder collection chamber. Accommodates the cartridge filter. A limited number of individual powder collection units are connected by a common duct to separate exhaust fan or blower units. Each exhaust fan creates a negative pressure in the associated powder collection unit and draws air-borne excess blast powder material from the booth chamber down through the floor of the booth, and then into each powder collection chamber. It is effective to put in. The over-sprayed powder material collects on the walls of the cartridge filter, through which "clean" air enters the clean air chamber associated with each powder collection unit. A pulsed air jet is regularly introduced inside the cartridge filter from an air jet valve located above the cartridge filter to drive away the powder that has accumulated on the walls of the filter, Drop onto the angled fluidization plate at the base of each powder collection chamber,
To be removed. Each powder collection chamber has an outlet connected to a common header pipe and a gate valve is located at each of its outlet lines. The system controller is effective to sequentially open and close the valves so that the collected powder material is removed from the various powder collection units in the order in which they are transferred to the recycle hopper associated with the powder kitchen. .

The structure of the powder collection and recovery system described in this specification includes:
There are several advantages. Since several exhaust or blower units are used, each of which is associated with a limited number of powder collection units, a more uniform and evenly distributed downward air flow results in a powder spray booth room , Along its entire length. This is an improvement over systems with a single exhaust fan or blower. This is because it proved difficult to obtain a uniform negative pressure with only one blower unit in a spray booth having an extremely long length necessary to apply a large object such as a car body. Because it is done. Maintenance of the powder collection and recovery system described herein is also much easier than that of conventional designs. For ease of access, a reverse air jet valve is placed on top of the powder collection unit to allow one operator to easily remove the cartridge filter from the powder collection chamber. Removing powder material from each powder collection chamber is also facilitated by the angled fluidization plate at its base, which helps to smoothly transfer powder from the chamber. Also, the walls of the powder collection chamber are made sufficiently thin to help oscillate and force the powder onto the perforated plate when back-spraying air is activated.

DESCRIPTION OF THE DRAWINGS The operation and advantages of the structure of the presently preferred embodiments of the invention will become more apparent when the following description is considered in conjunction with the accompanying drawings.

FIG. 1 is a partial schematic view of one embodiment of the present invention depicting one end of a powder spray booth including a portion of a powder collection and recovery system and a feed hopper, including a schematic view of a powder kitchen. is there.

FIG. 2 is an elevation view of the primary hopper and the powder receiving unit included in the powder kitchen.

  FIG. 3 is a plan view of the primary hopper shown in FIG.

FIG. 4 is a cross-sectional view taken generally along line 4-4 of FIG.

FIG. 5 is an elevation view of a partial cross-sectional view of one embodiment of the feed hopper of the present invention.

FIG. 6 is a schematic partial cutaway view of the robot hopper of the present invention.

FIG. 7 is a schematic partial cutaway view of the powder collecting and collecting system.

  FIG. 8 is an end view of the powder collection chamber.

9 is a side view of the powder collection chamber depicted in FIG.

FIG. 10 is a view similar to FIG. 1 except for another embodiment of the powder coating system of the present invention.

11 is an elevation view of a partial cross-sectional view of another embodiment of the feed hopper shown in FIG.

FIG. 12 is a graph showing the particle size distribution of an unused granular powder coating material by volume percentage.

FIG. 13 is a graph showing the particle size distribution of the regenerated granular powder coating material in terms of volume percentage.

FIG. 14 graphically illustrates the percentage of particulate powder coating material with a particle size of less than 10 microns present in the powder coating material having various percentages of virgin powder after a predetermined number of regeneration cycles. It is a set of value curves.

FIG. 15 is a block diagram depicting the measurement and control functions performed by the controller used in the embodiment of the invention shown in FIG.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, the powder coating system of the present invention
One embodiment of 10 is a powder spray booth 12, an apparatus for transferring powder coating material from a powder kitchen 14 to booth 12, and a powder collection and recovery system 16 associated with booth 12.
including. These system elements are described separately below and their operation is discussed.

Powder Spray Booth Referring to FIGS. 1 and 2, the powder spray booth 12 is
Ceiling 18, floor 20, opposite side walls 22, 24, and booth entrance
26 and an opposite end wall defining a booth exit 28.
See also FIG. 7. This spray booth 12 has a structure in which a central portion 36 extending in the vertical direction of the spray booth 12 is provided with a room 30 forming a control area for applying a powder coating material to an object such as a vehicle body 32 moved by a conveyor 34. Stipulate. Excessive spray powder material that does not adhere to the vehicle body 32
It passes through a grid 38 located along 20 and enters the powder collection and collection system 16 which will be described in detail below.

The powder spray booth 12 extends a considerable distance in the vertical direction,
Various powder spray guns can be arranged at various positions along the booth chamber 30 so that the powder coating material is applied to the entire area of the vehicle body 32 while passing through the booth chamber 30. For illustration, a robot 40 carrying a spray gun 42 is depicted on one side of the spray booth 12, and an overhead gun manipulator 44 is shown carrying a spray gun 47 at a position above the vehicle body 32. ing. Depending on the size of the vehicle body 32, the type of powder coating material applied, the desired coating area on the vehicle body 32 and other factors, it may be operated automatically or manually to coat the vehicle body 32 with the powder coating material. Basically, any number of spray guns can be provided along the length of the spray booth 12. The particular location and operation of such a spray gun does not form part of the present invention per se and is not discussed herein.

In the preferred embodiment of the present invention, the body 32 is conveyorized.
Maintained at ground potential by 34, spray gun 42 and
46 imparts an electrostatic charge to the powder coating material. The electrostatic charge imparted to the powder material increases the amount of powder that adheres to the vehicle body 32 and helps retain it, but still relatively large amounts of powder material are "oversprayed". That is, the car body
Does not adhere to 32. This oversprayed powder must be collected and collected during the powder coating operation, as described below.

1. Powder coating system of FIG. 1 An important aspect of the present invention is to add powder coating material to a powder kitchen.
The structure of the system 10 transferring from 14 to the spray booth 12. In many vehicle manufacturing facilities, the powder kitchen 14 is located far away from the spray booth 12, for example, tens to hundreds of meters (100s of feet), and a large amount of powder coating material quickly Must be transferred. Powder flow rate of 0.454 to 0.908 kilograms (1-2 pounds) per second and 136.2 kilograms (300 pounds) per hour
The above total demand is not uncommon. The overall construction of the powder transfer system of the present invention that can efficiently and economically satisfy such parameters will first be described, followed by the various discrete elements that make up such a transfer system. , Consider in detail.

In the embodiment of FIG. 1, the powder kitchen 14 is a basically closed enclosure (not shown), a “conditioned”, supplied from an air house (not shown) of conventional design. air,
That is, filtered and humidified air is provided. Inside the powder kitchen 14 is a supply 54 that contains unused powder coating material.
There is a first powder receiving unit which will be described in detail below.
Connected to 58 by line 56. Powder receiving unit
58 is connected to a primary hopper 60 and also by suction hose 61 to a first vacuum pump 62, both of which are housed in the powder kitchen 14; The primary hopper 60 is connected by a transfer line 64 to a second powder receiver 66 connected to a first feed hopper 68. This transfer line 64 is
It carries a gate valve 70 and is connected to a first make-up air valve 72, both downstream of the primary hopper 60, in the powder kitchen 14
Located inside. Make-up air valve 72 is connected to a pressurized air supply 73, which is schematically depicted in FIG. As shown at the top of FIG. 1, a second powder receiver 66 and a first feed hopper 68.
Is located in the vicinity of the powder spraying booth 12, but the transfer line 64 interconnects the primary hopper 60 and the second powder receiver 66.
Can be tens to hundreds of meters (several hundred feet) long. The supply hopper 68 is connected by a line 67 to a third vacuum pump 69 housed in the powder kitchen 14 and carries a powder pump 74 (see FIG. 5), which is connected by a line 76 to a robot hopper 78. Connected. Robot hopper 78 is connected by line 79 to spray gun 42 associated with robot 40.

As illustrated in FIG. 1, the right portion of the powder kitchen 14 includes a structure similar to that described above for the primary hopper 60. This part of the powder kitchen 14 supplies the collected excess spray powder, mainly from the collection and recovery system 16 of the powder spray booth 12, instead of receiving the unused powder coating material from the container 54. To be done. In a preferred embodiment of the invention,
The powder kitchen 14 has a recycle hopper coupled to a third powder receiving unit 82 of the same type as the receiving units 58 and 66.
Accommodates 80. The third powder receiving unit 82 is a third vacuum pump arranged in the powder kitchen 14 by a line 83.
Connect to 84 and regenerate suction line as discussed below.
Joined to the powder collection and recovery system 16 by 86. The second transfer line 88 carries a make-up air valve 92 and a gate valve 90 connected to an air supply source 73 and a regeneration hopper 80 to a fourth.
Interconnect with the powder receiving unit 94. The fourth powder receiving unit 94 is coupled to the second supply hopper 96 located near the powder spray booth 12. As schematically illustrated in FIGS. 1 and 5, the second feed hopper 96 includes a spray gun 46 associated with the overhead gun manipulator 44.
Includes a positive pressure powder pump 98 that supplies powder material through line 100. The fourth powder receiving unit 94 is connected by a line 104 to the fourth vacuum pump 102 located inside the powder kitchen 14.

In the preferred embodiment of the present invention, the primary hopper 60, the first feed hopper 68, the robot hopper 78, the recycle hopper 80 and the second feed hopper 96 are each a hardy.
Instruments Company (Hardy Instruments Co
mpany) is carried in a separate load cell 116A-E of the type commercially available under model numbers FLB-3672-1K and H1242 PS-C500. Load cells 106A-E are designed to reflect zero weight in the absence of powder coating material on each associated hopper,
"Zeroing" or adjusted. As discussed below,
Each load cell 106A-E operates to measure the weight or amount of powder coating material accumulated in its associated hopper and generate a signal representative of such a weight reading. The signal is sent to programmable logic controller 108 (PLC), which is Allen Bradley of Cleveland, Ohio.
Is preferably a type commercially available under the model number PLC-5. Controller 108 operates vacuum pumps 62, 71, 84 and 102, as well as valves 70, 72, 90 and 92, respectively, in response to signals from load cells 106A-E.

Operation of the Powder Coating System Illustrated in FIG. 1 The structure and operation of each of the individual elements of the powder coating system 10 will be discussed in detail below, the overall operation of one of which is outlined in FIG. It can be described with reference to the figures. Unlike many prior systems, the powder coating system 10 of the present invention uses negative pressure to convey powder coating material from the powder kitchen 14 to the powder spray booth 12. Further, the supply and transfer of the powder are basically automatically performed as the powder coating operation progresses.

Referring first to the left side of the powder kitchen 14, unused powder coating material is transferred from the source 54 when the controller 108 activates the first vacuum pump 62. First vacuum pump
62 creates a negative pressure in the first powder receiver 58, which draws unused powder coating material from the source 54 into the first powder receiver 58 through line 56. As described below,
The first powder receiver 58 discharges powder coating material into the primary hopper 60, and the amount of such powder coating material received is monitored by the load cell 106A associated with the primary hopper 60. When a predetermined level or quantity of powder coating material is present in the primary hopper 60, the load cell 106A sends a signal to the controller 108 indicating this condition, which causes the first vacuum pump 62 to operate.
To stop.

First supply hopper for powder coating material from primary hopper 60
The transfer to 68 is also carried out by applying negative pressure. The controller 108 activates the second vacuum pump 69 to generate a negative pressure in the second powder receiver 66 associated with the first feed hopper 68. This negative pressure draws the powder coating material from the primary hopper 60 into the transfer line 64 and passes through the gate valve 70, which is opened by the controller 108 upon activation of the second vacuum pump 69. The transfer of powder from primary hopper 60 is monitored by its load cell 116A, which sends a signal to controller 108 when a predetermined amount or weight of powder has been discharged from primary hopper 60. The controller 108 closes the gate valve 70 in the transfer line 64 to stop the flow of powder therethrough and switches off the second vacuum pump 69. The operation of filling the first feed hopper 68 with powder from the primary hopper 60 is performed by its associated load cell 106B monitoring the weight or amount of powder. When the amount of powder in the first feed hopper 68 falls below a predetermined level, the load cell 106B sends a signal to the controller 108, which will be discussed in detail below in the second powder receiver 66. Start the weighing device included in. Next, the powder transferred from the primary hopper 60 to the second powder receiver 66 is directed to the first supply hopper 68, and when a predetermined weight is obtained, a signal is sent from the load cell 106B to the controller 108. Thus, the measuring device in the second powder receiver 66 stops operating.

A first feed hopper, as shown schematically at the top of FIG.
The powder coating material in 68 is removed by the powder pump 74 by applying a positive pressure (see also FIG. 5), and transferred to the robot hopper 78 carried by the original load cell 106C via the line 76. To do. When the robot hopper 78 receives a sufficient amount of powder coating material, the load cell 106C monitors and the controller 108 stops the powder pump 74 and the second powder pump 77.
From the robot hopper 78 to the powder gun 42 via line 79 and associated spray gun 42 with the robot 40.
And apply to the vehicle body 32.

The purpose of the load cells 106A-E is to ensure that the flow rate and total amount of powder coating material transferred through the system meets the requirements of a predetermined number of car bodies 32 as they pass through the powder spray booth 12. Is to operate automatically. Load cell 106A associated with primary hopper 60, first feed hopper 68 and robot hopper 78, respectively.
C monitors the amount or weight of the powder coating material, and when the amount of powder falls below a predetermined level, the control device 108
To provide a signal to. When the controller 108 receives such a signal, the appropriate vacuum pump or metering device is activated to transfer the powder coating material to the hopper which has been depleted of the supplied coating material. This way, the hopper 60,
68 and 78 all provide a continuous and sufficient supply of powder coating material.

Due to the extreme length of the transfer line 64, a second vacuum pump
The powder kitchen 14 is operated so that there is no residual powder coating material in the transfer line 64 when 69 stops and the flow of powder coating material from the primary hopper 60 to the second powder receiver 66 is stopped. Including the arrangement configuration of. As mentioned above, the primary hopper
During the transfer operation from 60 to the second powder receiver 66, the controller 10
8 opens the gate valve 70 in the transfer line 64. Primary hopper 6
When the load cell 106A associated with 0 indicates that a predetermined amount has been discharged from the primary hopper, the controller
108 stops the second vacuum pump 69 in the powder kitchen 14, closes the gate valve 70 and opens the make-up air valve 72. Next, the pressurized air from the air supply source 73 passes through the makeup air valve 72 and enters the transfer line 64, and the coating material remaining on the upstream side of the transfer line 64 receives the second powder receiver from the powder kitchen 14. "Catch up" to 66, that is, actively forcibly transfer. As a result, the accumulation of the powder coating material in the transfer line 64 is almost prevented, and the subsequent transfer operation of the powder from the primary hopper 60 to the first supply hopper 68 is executed quickly and efficiently. be able to.

Referring to the right-hand portion of powder kitchen 14 and the upper-right portion of FIG. 1, the components of the powder transfer system that supply powder coating material to spray gun 46 are depicted. As discussed above, such elements include a recycle hopper 80, a third powder receiver 82 and third and fourth powder hoppers 80 within the powder kitchen 14.
It includes vacuum pumps 84, 102 and a fourth powder receiver 94, a second supply hopper 96 and a third powder pump 98 located near the powder spray booth 12. The structure and operation of these elements is basically the same as the corresponding elements in the left part of FIG. Such elements primarily carry the collected overspray powder coating material received from the collection and recovery system 16.

In order to fill the reclaim hopper 80 with oversprayed powder material, the controller 108 activates the third vacuum pump 84 to create a negative pressure in the third powder receiver 82 and through the recycle line 84. The powder coating material is sucked into the third powder receiver 82 from the collection / recovery system 16. The third powder receiver 82 loads excess sprayed powder material into the recycle hopper 80 in a manner discussed in detail below.
The amount of powder entering the recycle hopper 80 is monitored by the load cell 106D associated with it. The control device 108 is the fourth
When the vacuum pump 102 is activated, the powder material is transferred from the regeneration hopper 80 to the fourth powder receiver 94 and the second supply hopper 96. The negative pressure generated in the fourth powder receiver 94 sucks the powder from the regeneration hopper 80 through the gate valve 90 opened by the control device 108 into the second transfer line 88, and the fourth powder receiver 94. Put in 94. The second feed hopper 96 receives such powder from the fourth powder receiver 94, the amount of which is monitored by the load cell 106E associated therewith, and the positive pressure powder pump 98 then feeds the powder. From the second feed hopper 96 via line 100 to the spray gun 46 carried by the manipulator 44. The operation of the vacuum pumps 84 and 102 and the metering device associated with the fourth powder receiver 94 is performed in the same manner as discussed above, namely load cell 106D and load cell 106D and associated with recycle hopper 80 and second feed hopper 96, respectively. Controlled by the controller 108 in response to the signal from 106E. Positive pressure powder pump 9
The operation of 8 is also controlled by the control device 108 depending on whether or not the vehicle body 32 is present in the powder spray booth 12. Valves 90 and 92 in powder kitchen 14 function in the same manner as valves 70 and 72 described above.

Before examining each of the individual elements associated with the powder transfer system in more detail, it is worth mentioning two additional features of the powder transfer system. Depending on the application, the total amount of powder coating material required for the recycle hopper 80 may exceed the amount of oversprayed powder coating material supplied by the collection and recovery system 16. To ensure that there is always a sufficient amount of powder coating material in the recycle hopper 80, the primary hopper 60, which contains unused powder coating material, is connected to the mini-cyclone 114 carried by the recycle hopper 80 in line 112. Powder pump connected by 110
including. This mini-cyclone 114 is model number PC-4- from Nordson Corporation of Amherst, Ohio.
It is marketed in 2. If the load cell 106D associated with the recycle hopper 80 senses that the powder material in the recycle hopper 80 is below the required weight and the powder cannot be adequately supplied from the collection and collection system 16, the controller 108 will recycle the powder. Start the body pump 110 to remove unused powder coating material,
It is transferred to the regeneration hopper 80 through the line 112 and the mini-cyclone 114, and the total amount of the powder is replenished. If such a transfer is required, both the virgin powder coating material and the powder coating material from booth 12 that has been oversprayed and collected is mixed in the recycle hopper 80, and then, as described above. Supply the spray gun 46 in the same manner.

Yet another aspect of the powder transfer system shown in FIG.
A vent utility collector 116 is used that is located within the powder kitchen 14 and is connected by a line 118 to a vent 120 at the top of the primary hopper 60. Similarly, a second vented utility collector 122, also included in powder kitchen 14, is connected by line 124 to vent 126 of reclaim hopper 80. Ventilation utility collector 11
6 and 122 vent the interior of the primary and recycle hoppers 60 and 82, respectively, to remove "fines" from above the interior of such hoppers 60 and 82. As used herein, the term "fines" is typically concentrated near the upper portion of the powder feed hopper and does not electrostatically charge when discharged from a spray gun, such as spray guns 42 and 46, Refers to particles of very small diameter powder material of less than 10μ that also do not have a sufficient moment to reach the object to be coated. Such small particles are usually not attracted to the surface of the object to be coated and thus tend to accumulate in the system, reducing the coating efficiency and thus the percentage of particles adhering to the object to be coated. Therefore, it is advantageous to remove these small particles or fines with the aeration utility collectors 116 and 112 within the powder kitchen 14 for subsequent disposal.

Powder Coating System and Method of Operation of FIG. 10 Referring to FIG. 10, powder coating system 50 according to the present invention.
Another embodiment of 0 is schematically illustrated. Because powder coating system 500 includes some of the elements shown in FIG. 1 and described above, the same reference numbers are used in FIG. 10 to identify structures in common with FIG.

The distinction between the system 500 of FIG. 10 and the system 10 of FIG.
It is mainly based on the recognition that in certain spraying applications using various types of virgin powder coating materials, care must be taken to avoid excessive accumulation of "fines".
The term "fines" refers to powder particles that are less than about 10 microns in size. As mentioned above, excessive buildup of fines results in poor fluidization in the hoppers 60, 68, impingement fusion on the parts to be painted, clogging of filter cartridges and screens, spray booth 12 and various types. It has been found to cause problems with increased powder accumulation in the coating dispensers 42, 46 and reduced coating efficiency. For many types of powder coating materials, one or more of the problems listed above will occur if 30% or more of the total amount of powder coating material accumulates. The proportion of fines that causes problems is different.

In addition to concerns regarding the buildup of excessive amounts of fines in the powder coating material supplied to the spray guns 42, 46, the appearance of the finished product should also be considered when coating the powdered coating material. It should be an element. For example, the surface finish tends to deteriorate as the proportion of relatively large or coarse particles increases. For example, particles larger than about 70 microns do not flow on the surface of the part to be coated to the same extent as particles of about 10 microns, thus resulting in a rough surface finish. In contrast, smaller particles have a better surface finish, but when the relative proportion of such small particles exceeds a certain level, the above problems prevail.

To address the problem of retaining an acceptable surface finish while suppressing the buildup of excess fines, the system 500 shown in FIG. 10 includes a pair of supply lines 504, 505 to contain virgin particulate powder material. It is connected to the mixing hopper 502 which is connected to the primary hopper 60 and is connected by a pair of feed lines 506, 507 to the recycle hopper 80 which receives the oversprayed powder from the booth 12 as described above. Gate valve 508 is 1
A gate valve 509 is attached to each of the supply lines 504 and 505 extending from the next hopper 60 to the mixing hopper 502, and to each line 506 and 507 between the regeneration hopper 80 and the mixing hopper 502. The mixing hopper 502 was connected to the fourth powder receiving unit 94 by a transfer line 512, which in the embodiment of FIG. 1 was connected to the recycle hopper 80 by a line 88.

Other than the above, another structural difference between the coating system 10 and system 500 shown in FIG. 1 is that a single vacuum pump 51 connected by line 516 to each powder receiver 66 and 94.
Is to use 4. As mentioned above, the embodiment of FIG. 1 uses two vacuum pumps 69 and 102 to
It provided a negative pressure to transfer the coating material to powder receivers 66 and 94, respectively. Also, in FIG. 10, one ventilation utility collector 518 is used in place of the two ventilation utility collectors 116, 122 depicted in FIG. The ventilation utility collector 518 has a larger capacity than that described above and is connected to the filter unit 522 by a line 520, as shown in the right part of the powder kitchen 14 in FIG. The filter unit 522 is connected to the fan 526 by a duct 524. Ventilation utility collector 5
18 to the primary hopper 60 by line 519, line 521
To the recycle hopper 80 and to the mixing hopper 502 by line 523.

As mentioned above in connection with the discussion of venting utility collectors 116, 122 of FIG. To remove excess particulates and avoid the same attendant problems as described above. Nevertheless, the ventilation utility collectors 116, 112 and 518
As such, it is sufficient to adequately control the relative volume percentage of fines in the overall mixture of virgin powder coating material and recycled powder coating material supplied to at least a portion of the spray gun. is not.

The powder coating system 500 of FIG. 10 operates in the same manner as described above in connection with FIG. 1, except that a mixture of virgin powder coating material and recycled or oversprayed powder coating material is
It is supplied to the painting dispenser 46. As shown in FIG. 1 and described above, the system 50 of the present invention does not directly feed the oversprayed powder material from the recycle hopper 80 to the gun 46.
0 mixes unused powder coating material with over-sprayed or regenerated powder coating material in an appropriate volume percentage to prevent excess fines from accumulating in the mixing hopper 502, and to supply dispenser 46 for coating. With such a mixture being
Methods and means of operation are provided that ensure that a suitable particle size distribution is obtained. Unused powder supply line
Gate valves 508 associated with 504, 505 and gate valves 509 associated with reclaimed powder supply lines 506, 507.
Is operated by the controller 108 according to a mathematical model executed by software in the controller 108. The purpose of the mathematical model is to predict the particle size distribution in the mixing hopper 502 during steady state operation, which allows for "stable" operation, i.e. without excessive fines and easy fluidization. Regeneration hopper 80 to obtain a powder mixture that can be pumped and sprayed onto the parts to be painted
It is possible to determine how much unused powder coating material must be added from the feed hopper 60 to the mixing hopper 502 for combination with regenerated or over-sprayed powder from the hopper 502.

Referring first to FIGS. 12 and 13, the particle size distribution within the powder coating material is graphically depicted. The term "particle size distribution" refers to the volume percentage of powder particles in a particular size range of a given powder coating material sample. Figure
The 12 is made by Ferro of Cleveland, Ohio, and is No.158E11.
4 shows the particle size distribution of an unused powder coating material sold as No. 4. This virgin powder coating material has a median particle size of 22 microns and the data points shown in the graph are the total volume percentages of 16 particle size ranges within this type of virgin powder coating material, Physical measurements were made with a laser diffractive particle size analyzer such as the Malvern PSD analyzer commercially available from Malvern Instruments, Inc. of Southborough, Massachusetts. The particle size range of 16 is 0.5-1.9μ, 1.9-2.4μ, etc.,
A range chosen for ease of illustration and it is contemplated that various other particle size ranges may be used in the following description of the method of the present invention.

FIG. 13 is a graph similar to FIG. 12, but after applying an unused powder coating material to a predetermined vehicle body 32 in the booth 12,
FIG. 3 shows a particle size distribution in the particulate powder coating material regenerated or collected from the powder spray booth 12. That is, FIG. 13 shows the particle size distribution of the powder coating material that did not adhere to the vehicle body 32 in the spray booth 12 after the spraying operation was performed once with the unused powder coating material shown in FIG. Show. Figure 13
The particle size distribution of the powder shown in Fig. 12 was also measured with a Malvern PSD analyzer, and as shown in the figure, for the over-sprayed powder sample after one pass in Fig. The proportion of smaller particles is higher. This is generally because larger powder particles are more easily and efficiently charged with static electricity by the coating dispenser 42 or 46 before they are deposited on the object, and such larger particles have a greater mass.
This is because the moment for flowing to the vehicle body 32 in the spray booth 12 is large.

The purpose of the mathematical model of the present invention is to introduce a sufficient amount of fresh powder coating material from the primary hopper 60 into the mixing hopper 502 continuously during the steady operation of the system 500 to accumulate excess fines. To maintain an acceptable overall particle size distribution, i.e. booth 12
To mathematically predict the particle size distribution of the powder that does not adhere to the vehicle body 32 inside.

In order to calculate the change in particle size distribution over time, the probability of particles remaining in the system must be determined. A method for obtaining the probability coefficient for each size range of the distribution will be briefly described below, and then mathematically detailed. Its purpose is to find a set of numbers (probability coefficient) which, when multiplied by the unused particle size distribution, gives a size distribution of oversprayed particles.

(I) First, the ratio of the size distribution of unused particles to the size distribution of regenerated particles is obtained for each size range. This percentage is a measure of the relative tendency of different particle sizes to be attracted to the part. Particle sizes having a ratio of 1 or greater are more likely to be attracted to the part than particle sizes having a ratio of less than 1. This latter particle tends to remain in the system.

(Ii) Then normalize the cumulative sum of the data from paragraph (i) to 1.00 and the probability distribution is still 10 for all particles.
Guaranteed to reflect 0%.

(Iii) The probability that the powder remains in the system is calculated by normalizing by subtracting the above probability distribution of each particle size from the value of "1". However, this mathematical operation still does not provide the necessary probability distribution. What is sought is a set of numbers that, when multiplied by the size distribution of virgin particles, yields a size distribution of oversprayed particles.

(Iv) Use an appropriate multiplier for each particle size in the distribution in paragraph (iii) above to obtain a good match between this calculated particle size distribution and the particle size distribution of the oversprayed powder. .. If you normalize this new set of numbers,
The resulting value is the particle size distribution for each cycle through the system multiplied by a probability factor.

The first step of the method outlined above is the Ma
The lvern PSD analyzer is used to physically measure the particle size distribution Fv of the virgin powder coating material used for a given coating application. This material is then sprayed into the spray booth 12 of the given configuration with the particular vehicle body 32 to be painted, and then the oversprayed or reclaimed powder coating material is collected. For purposes of this discussion, such oversprayed powder material is referred to as "one-bath reclaim", i.e., a powder regenerated after a single "bath" or spray operation. Next, the particle size distribution of 1-bus reproduction is physically measured to obtain Fr.

As can be seen in Figures 12 and 13, particle size "distribution" refers to the combined volume percentage of 16 distinct particle size ranges from 0.5 microns to 188 microns. Therefore, the term
Fv and Fr are expressed as follows.

Fv = Fv ₁ to ₁₆ (1) = Fv ₁ Fv ₂ ... Fv ₁ to ₁₆ where Fv ₁ = volume percentage of particles of an unused powder coating material having a size of 0.5 to 1.9μ, Fv ₂ = The volume percentage of the particles of the unused powder coating material having a size of 1.9 to 2.4μ, ...

Fr = Fr ₁ to ₁₆ (2) = Fr ₁ , Fr ₂ , ... · Fr ₁ to ₁₆ where Fr ₁ = 0.5 to 1.9μ of 1-pass regenerated powder coating material particle volume percentage, Fr ₂ = Volume percentage of particles of the 1-pass regenerated powder coating material of 1.9 to 2.4μ, ...

The measured particle size distributions Fv and Fr are calculated by the controller 108.
, Which can calculate the quotient of the particle size distribution as follows.

The quotient obtained from equation (3) above is then normalized according to the relationship:

This is achieved in a two-step process, but first the Fv / F
Find the quotient of r ₁ , that is, S.

The various quotients were then "normalized" for each of the 16 particle size ranges shown in the graphs of Figures 12 and 13.
Calculate the value as follows:

The following sequence of calculations performed by the software of controller 108 allows, for example, P ₁ to ₁₆ for each particle size range.
A solution of the probability coefficient P such as Probability coefficient P ₁ ~
₁₆ determines the probability that particles will remain in the system 500, i.e., will not be attracted to the carbody 32 in the booth 12, and will therefore be regenerated as overspray powder, in each of the 16 size ranges shown in FIGS. 12 and 13. Represent This information is important because, as mentioned above, system stability depends on the mixing hopper 502.
This is because it depends on maintaining the volume percentage of the fine powder inside below a predetermined level such as 30%. Probability coefficient P ₁
The formula used to find ~ ₁₆ is given by:

Where F _A = part after the F _A term adjustment factor x = integer 1 to 16 P = probability factor P _1, P ₂ ··· P ₁₆ Equation (7) is obtained by the following two-step calculation. First, the coefficient Z is calculated as follows.

Next, the quotient obtained from the calculation based on the equation (8) is normalized to 1.

The quotient obtained from the calculation based on equation (9) is
Normalized values are shown for each of the 16 particle size ranges in the 12 and 13 graphs. This value is then used in equation (7) to represent the probability coefficient P for each particle size range, that is, the probability that each size range will remain in the system (not stick to the part) after a particular painting operation.

For example, equation (7) can be written to determine the probability factor P ₁ for powder particles having a first group of particle sizes of 0.5-1.9 microns as follows.

For each of the 16 groups of particle sizes, the "adjustment factor" F _A can be empirically determined by trial and error, so the following equation is more accurate than the actual measurements of fresh and one-pass regenerated particles: .

Fr ₁ ≈ Fv ₁ · P ₁ (11) Fr ₂ ≈ Fv ₂ · P ₂ (12) Fr ₁₆ ≈ Fv ₁₆ · P ₁₆ (13) That is, as described in equations (1) and (2), Diffraction particle size analyzer first particle size distribution
The actual measured values of Fv and Fr are used to derive a suitable adjustment value F _A to ensure that the final mathematical calculation of Fr ₁₆ is as accurate as possible. Given the type of powder coating material described above, the actual adjustment factors F _A1 to ₁₆ for the particle size range increasing from 0.5-1.9μ to 87.2-188μ are 1.0, 0.95, 0.90 ... 0.25 respectively. Preferably there is.

Once the probability factors P ₁ to ₁₆ have been calculated respectively as described above, this value must also be normalized to 1.0 in the same way as above. Now the results normalized values obtained P ₁ ~ _16, for example, subjected to particle size distribution of the unused powder, used as a multiplier, overspray particle size distribution of each cycle through the apparatus 10 Can be predicted mathematically.

The above discussion is simply based on the assumption that no other unused powder material will be added to the system and the original amount of powder material will be recycled during the continuous painting operation. It was based on a mathematical model. Under normal operating conditions, the powder coating material adheres to objects such as the carbody 32 in the booth 12 and must be constantly replaced, so to approximate the actual operation of the system 500, a predetermined fraction of A mathematical model is needed in which virgin powder material is added to the system.

In the above, the calculations given by equations (1) to (13) are not repeated, and the following relational equations are used to obtain from equations (11) to (13)
The particle size distribution of path regeneration is shown.

Fr = Fv · P (14) Therefore, the term Fr represents the particle size distribution within the first pass reclaimed powder as calculated using the mathematical model of equations (1)-(13).

Taking into account the addition of the volume fraction y of new virgin powder added to the reclaimed powder after the first pass or painting operation, normalized to 1.0 in equation (14), the following relation is derived:

Fr _i y = (1-y) Fr _i + yFv (15) where y = volume fraction of unused powder coating material added to the system after collection of 1-pass reclaimed powder, Fr _i y = fraction The particle size distribution of the 1-pass reclaimed powder containing the unused powder coating material of y, i = the index of the number of passes starting from the unused powder coating material.

Once the value of Fr _i y is calculated, the particle distribution of the subsequent “pass” or painting operation can be expressed as:

Fr _{i + 1} = Fr _i y · P (16) Equation (16) is normalized to 1.0, and then the following calculation is performed.

Fr _{i + 1} y = (1-y) · Fr _{i + 1} + yFv (17) The term Fr _{i + 1} y is a particle in the second pass regenerated powder (i + 1) containing the unused powder of the fraction y. Represents the distribution.

This same series of calculations is repeated for a number of cycles to produce the type of curve depicted in the graph of FIG. FIG. 14 shows the volume percentage of fines present when spraying the Ferro 158E 114 powder coating material with varying percentages or volume percentages of virgin powder. Each curve in the graph of FIG. 14 represents various volume percentages of the virgin powder y in the reclaimed powder, depicting how the volume percentage of the powder changes with the number of cycles or continuous painting operations. Based on the calculations from equations (15) and (17), and its iterative method for total particle size (i + 16), the calculated particle size distribution over the entire 16 particle size range is obtained. The software of controller 108 is activated to sum the calculated volume percentages of all particles less than or equal to 10 microns in each of the 16 size ranges, and for each successive cycle or painting operation, the vertical column of the graph in FIG. The coordinate value is obtained. To illustrate how the volume percentage of fines changes with successive cycles and changes with the change of virgin powder to reclaimed powder, by way of illustration, several different values of y are calculated, Included in Figure 14.

The curve in Figure 14 shows a median particle size of about 22 microns.
Ferro 158E114 virgin powder coating material was used to mathematically derive from the above equation. For this type of material, it has been found to be desirable to keep the volume percentage of fines below about 30% to avoid the problem of excessive fines accumulation described above. From the graph of Figure 14, to maintain a fine powder volume percentage of less than 30%, the
It is observed that it is advisable to add to the 500 more than 65%, or about 70% fraction y, of virgin powder. This is done by the operation of controller 108, which
Each line 504 from the primary hopper 60 to the mixing hopper 502,
A gate valve 508 of 505 and a gate valve 509 of each line 506, 507 extending between the regeneration hopper 80 and the mixing hopper 502 are selectively opened and closed.

As mentioned above, the mathematical model used here is
Useful for showing the percentage of fines in the mixing hopper 502 for powder coating materials containing various volume percentages of virgin powder. This allows an appropriate volume fraction of fresh powder to be added to the mixing hopper 502 to prevent excessive fines from accumulating in the mixing hopper 502 during steady operation of the system 500. As a safety measure, the system 500 of the present invention
Monitors the particle size distribution in the mixing hopper 502,
Software that ensures that the percentage of actual fines in the mixing chamber 502 matches the value predicted by the mathematical model,
Included within controller 108.

Referring to FIG. 15, there is a flow chart that graphically illustrates a sequence of operations for performing the above monitor functions. First, manually pull the sample from the mix hopper 502,
Using the same laser diffraction particle size analyzer as above, as outlined in block 528, mix hopper
The actual particle size distribution F _M in the 502 measurement. Particle size distribution information is entered manually or electronically from block 528 into controller 108 via line 530. afterwards,
All of the tasks depicted in FIG. 15 are performed electronically by software in controller 108. Controller 108 operates to calculate the volume percentage of fines, such as particles less than about 10 microns, contained in mixing hopper 502. Block 53
See 2. One value representing such a calculated volume percentage is entered by line 534 into block 536, where the calculated volume percentage of fines and the calculated volume percentage for the particular type of powder coating material applied by system 500. Compare to a given maximum volume percentage. In the illustrative embodiment shown in FIG. 15, block 536 nominally shows a desired maximum volume percentage of 30%, while other types of coating materials have other minimum volume percentages of fines. It is understood that it may be appropriate in some cases. If the calculated percentage of fines is 30% or less, line 538 sends a "NO" signal back to block 528 until the next monitoring period begins, for example, one day, one week, or any other desired period. , The monitor sequence has ended.

If it is determined at block 536 that the calculated percent fines is 30% by weight above the powder in the mixing chamber 502, a signal is sent from block 53 to block 542 through line 540. Controller 108 as indicated by block 542.
The calculation performed by empirically selects a weight fraction W, that is, a fraction such as 20% or 30%. Then, the controller 108 solves the following equation using the selected weight fraction W.

Ff = W · Fv + (1-W) · Fm (18) where Ff = desired volume percentage of fines in the mixing hopper, eg <30%, W = weight fraction of virgin powder, Fm = Particle size distribution of powder in the mixing hopper, Fv = particle size distribution of unused powder.

When the value of Ff becomes larger than 30% at the selected weight fraction W, another weight fraction W larger than this is selected, and the calculation using the equation (18) is repeated.

The next step in the monitor sequence shown in Figure 15 is:
The use of a load cell 106 of the type described above in connection with FIG. 1 to meter the powder in the mixing hopper 502. See Box 544. The actual weight of the powder in the mixing hopper 502 is then compared to the total weight capacity of the mixing hopper 502, and a signal representing the calculation is blocked via line 548, as shown schematically at block 546. Enter in 550. If the level of powder in the mixing hopper 502 is less than or equal to 1-W, as indicated by block 550, the controller 102 is actuated to put unused powder coating material into the mixing hopper 502 (block 552). If the mixing hopper 502 is full and cannot receive fresh powder coating material with a volume fraction W needed to reduce the volume fraction of fines to a desired level, ie> (1-W), the controller 108. Discharges a sufficient amount of powder from the mixing hopper 502, as indicated by block 554, and then adds fresh powder coating material. 50 mixing hoppers to make room for adding unused particulate powder coating material
The amount of powder that must be released or removed from 2 is
It can be obtained from the following relational expression.

Here, the fraction of the powder emitted from Q _D = mix hopper, MH _W = weight measurements of the mixing hopper capacity MH _C = mixing hopper is.

Therefore, the above series of weight calculations is based on the mixing hopper.
There is sufficient capacity in 502 to receive the fresh virgin powder coating material, thus ensuring that the mixing hopper 502 does not overflow and the overall volume fraction of fines is reduced. After adding unused powder coating material (block 552), the monitoring operation is complete until the next monitoring period.

Therefore, the above method of maintaining the desired ratio of recycled powder coating material to virgin powder coating material in the mixing hopper 502 is based on the mixing hopper 50 as the coating operation progresses.
2 depends on measuring the weight loss. Alternatively,
It is believed that an appropriate amount of reclaimed and virgin powder coating material can be supplied to the mixing hopper 502 based on flow rate measurements rather than weight measurements. In this embodiment, the flow rate of the powder coating material discharged from the mixing hopper 502 is monitored over time, and a recycle hopper 80 is respectively used by using a flow rate control device such as a screw feeder (not shown). And from the primary hopper 60, a predetermined amount of both reclaimed powder coating material and virgin powder coating material is added to the mixing hopper 502. The screw feeder or similar device associated with the primary hopper 60 and the separate screw feeder associated with the recycle hopper 80 are
Mix hopper in response to signal from mix hopper 502 or with additional unused powder coating material and recycled powder coating material
It is preferably activated by controller 108 after a predetermined period of work to be introduced at 502, or both.

Powder Receiver Referring to FIG. 2, the powder receiver 58 described above in connection with the discussion of the system 10 of FIG. 1 is illustrated in detail. It is understood that each of the other powder receivers 66, 82 and 94 is structurally and functionally equivalent to powder receiver 58, and therefore only one of the powder receivers will be discussed in detail herein. I want to. Also, an alternative embodiment of the powder receiver 600 is disclosed below in connection with FIG.

The powder receiver 58 includes a collector housing 128 having a hollow interior 130 with a plate 134 attached to the cartridge filter 132. Since the access panel 136 is fixed along the one side of the collector housing 128 by the latch 138 so as to be opened, the cartridge filter 132 can be accessed. The inside 130 of the collector housing 128 has a vent 14
It is vented by 0 and its upper end is closed by a cap 143 fixed by a latch 144. The cap 142 is a plate
Mount a reverse air jet valve 146 aligned with the open end of the cartridge filter 132 connected to 134. Reverse air jet valve 146 is connected to accumulator 150 by line 148.
Which is connected to a source 73 of pressurized air which is shown schematically in FIG. The cap 142 is the first vacuum pump 62.
Suction hose from or fitting connected to line 61
It carries 154. The lower portion of collector housing 128 includes a powder inlet 158 connected to line 56 from the container carrying the fresh powder coating material. The collector housing 128 tapers downwardly from the powder inlet 158 radially inwardly to form a tapered base 160 including an outer flange 162, as shown in FIG.

As discussed above, in order for the load cell 106A associated with the primary hopper 60 to function properly, this must be "zeroed" without the primary hopper 60 being completely powder coated. So you have to set the weight reading to zero. By this method, the load cell 106A only weighs the powder coating material that actually enters the primary hopper 60.
To ensure an accurate reading of the powder weight in the primary hopper 60, all the elements associated with the first powder receiving unit 58, independent of the primary hopper 60, are shown in the frame shown in FIG. Support on 164. The frame 164 includes a top plate 166 supported on vertical legs 168, a sloping brace 170 extending between the top plate 166 and the vertical legs 168, and one or more horizontal positions in the middle between the vertical legs 168. Includes support 172.

The collector housing 128 is an external flange of the collector housing 128.
A frame 164 is provided by a bolt 174 extending between the 162 and the upper plate 166.
It is attached to the upper plate 166. Extending downwardly from the tapered base 160 of the collector housing 128 is the collector housing 128.
Primer Pneumatics, Inc. of Salina, Kansas
c.) is a flexible sleeve 176 which connects to a rotary air lock metering device 178 of the type commercially available under model number MDR-FG-76-10NH-2-RT-CHE-T3. Weighing device 1
78 is drivingly connected by a belt (not shown) to the output of a motor 182 carried on a support plate 184 connected to one vertical leg 168. The motor 182 is activated and the weighing device 178
A series of inner blades 186 therein are rotated to transfer a metered amount of powder coating material from the tapered base 160 of the collector housing 128 to a rotary sieve 196 mounted on a horizontal support 172. The rotary sieve 196 is model E-240 manufactured by Azo Incorporated of Germany.
It is a commercial product of the type manufactured and sold by. The rotary screen 196 transfers the powder coating material through the second flexible sleeve 198 to the powder inlet 200 of the primary hopper 60. This is illustrated in more detail in FIG. 3 and described below.

In operation, the first vacuum pump 62 is activated by the controller 108 to create a vacuum along the suction hose or line 61 and a negative pressure in the hollow interior 130 of the collector housing 128. This draws unused powder coating material from the supply container 54 through line 56 and powder inlet 158 into the hollow interior 130 of collector housing 128. A portion of the powder coating material falls by gravity onto the tapered base 160 of the collector housing 128, and a portion of the powder coating material collects on the walls of the cartridge filter 132. Pressurized air, periodically supplied from accumulator 160, is conveyed in pulses through a reverse air jet valve 147 aligned with cartridge filter 132. This jet of air allows the powder coating material that has collected on the walls of the filter 132 to separate and drop downwards onto the tapered base 160 of the collector housing 128.

Depending on the operation of the motor 182, powder coating material
As it is transferred from the collector housing 128 by the lock metering device 178, a metered amount of powder coating material is delivered to the rotary screen 19.
Enter 6. After the powder coating material has passed through the rotary sieve 196,
Passing through flexible sleeve 198 by gravity, 1
It falls to the powder inlet 200 of the next hopper 60. When a predetermined amount of powder coating material has accumulated in the primary hopper 60, its associated load cell 106A sends a signal to the controller 108 which deactivates the first vacuum pump 62. As mentioned above, all other powder receiving units 66, 82 and 94 of the powder transfer system of FIG. 1 are structurally and functionally identical.

Referring to FIG. 11, another embodiment of the powder receiver 600 is
It is illustrated in detail. The powder receiver 600 is partially similar to the powder receivers 58, 66, 82 and 94 described above in connection with the discussion of FIG. 2 and in FIG. 11 the same reference to identify structures in common with FIG. Use numbers. Powder receiver 600 and powder receiver 58
One difference with is the structure for transferring the powder coating material from the collector housing 128 to the primary hopper 60. It has been found that in applications with certain types of powder material, the coating material may arch or bridge in the area of the tapered base 160 of the powder receiver 58, resulting in intermediate flow stops. . When the tapered base 160 is occluded, the powder coating material cannot pass through the airlock metering device 178 and into the rotary sieve 196 of the construction shown in FIG. Also,
The powder receiver 600 of FIG. 11 does not include the sieve 196, but the hopper 60
It is believed that the particulate powder coating material can be sieved prior to being introduced into the hopper 60 by placing it on top of. It is preferred to use sieve 196 at least at the points where powder coating material is first introduced into the system, such as pans 58 and 82. See FIG.

The powder receiver 600 of FIG. 11 is basically composed of the upper part of the powder receiver 68 of FIG. 2, and the lower part includes a structure for fluidizing the powder coating material toward the collector housing 128.
Can be smoothly transferred. The bottom of the collector housing 128 defines an interior containing a fluidized bed 602, which includes a cap 142 and a perforated plate extending outwardly from the side wall of the collector housing 128 and supported by a bracket (not shown) on the side wall. It extends between 604. The second area within the base of the collector housing 128 is
An air plenum 608 extending between a circular mounting plate 610 and a perforated plate 604 carried by a bracket mounted to the side wall 129 of the collector housing 128. A third section within the base within the collector housing is a motor chamber 612 that extends between the bottom wall 614 of the collector housing 128 and the mounting plate 610. For purposes that will become apparent below, the entire powder receiver 600 is preferably mounted on top of the support stand 615 at a position vertically above the primary hopper 60 or other hopper.

At the base of the feed hopper 600 is an agitator 616, which includes a motor 618 carried within a motor chamber 612 by a motor mount connected to a mounting plate 610.
The output of the motor 618 is drivingly connected to a shaft 622 that is rotatably carried in a bearing 624. The bearing 624 is mounted to the mounting plate 610 by a bearing mount and is mounted on the air plenum 6
It extends vertically upward through 08 to a position just above the perforated plate 604. At least two entrainment arms 628 are secured to the top of shaft 622 extending through bearings 624 by lock nuts 630, so that entrainment arms 628 are perforated according to the operation of motor 618. 6
For 04, rotate in the position above it.

Air supply line 636 entering one side of motor chamber 612
, At least two air inlets 632 are connected by pipes in a manner not shown. This air supply line
It is connected to a source 73 of pressurized air. Upward air flow enters the air plenum 608 through the air inlet 632 where the air is deflected by the baffles 638 mounted on the bearings 624. The purpose of this baffle is disclosed in detail in US Pat. No. 5,018,909 owned by the assignee of the present invention, the disclosure of which is hereby incorporated by reference in its entirety.

The transfer pipe 640 has one end on the perforated plate 604 and the fluidized bed 60.
Inside 2, the collector housing 128 is connected. Transfer pipe 640
The other end of is attached to the inlet 642 of the primary hopper 60. Rotary air lock 178 is driven by motor 182 and is connected in transfer tube 640, both of the same types described above in connection with powder receiver 58 considerations. Figure 1
The operation of the motor 182 is shown in FIG.
8 and thus also the operation of the rotary air lock 178. The powder coating material from the fluidized bed 602 in the powder receiver 600 flows downward by gravity according to the operation of the rotary air lock 178, passes through the transfer pipe 640, and then inside the primary hopper 60. to go into. The motor 182 is stopped, turning off the rotary air lock 178 as desired, stopping the flow of powder coating material through the transfer tube 640. This configuration of the powder receiver 600 provides a smooth transfer of powder to the primary hopper 60, such a powder receiver 600 shown in FIG.
And 10 could be used as an alternative to both embodiments. Otherwise, the powder receiver 600 functions in the same manner as the powder receiver 58 described above, and discussion of such operation will not be repeated here.

Primary and Recycle Hopper The primary hopper 60 and recycle hopper 80 are essentially identical to each other and, for discussion purposes only, only the primary hopper 60 is shown and described in detail. Referring to FIGS. 3 and 4, the primary hopper 60 includes a housing 202 having an inner wall 204 generally in the shape of a “figure eight”. Therefore, the inner wall 204
Includes two circular sections 206 and 208, which are defined by opposing triangular baffles 212 and 214, each connected to one side of housing 202, and meet at a reduced diameter area 210 in the center of housing 202. . The baffles 212, 214 each have a pair of side panels 216, 218 that extend inwardly from the walls of the housing 202 and meet to form a top 220 toward the center of the housing interior 203.

As best seen in FIG. 4, the perforated plate 222 is
Carried by mount 224 near the base of the housing inside 2
03 is separated into a fluidized bed 226 between the perforated plate 222 and the top wall 229 of the housing 202 and an air plenum 230 located between the perforated plate 222 and the bottom wall 232 of the housing 202. To do. Air Plenum 230
Includes a number of baffles 270 and a generally U-shaped perforated air tube 272. The bottom wall 232 is located on top of the load cell 106A discussed above in connection with the powder transfer system of the present invention.

The upper wall 228 of the casing 202 has a first stirrer 234 and a second stirrer 2
36 and the upper wall 22 with the handle 240 and the latch mechanism 242.
Supports access cover 238 attached by hinge 243 to opening 244 in eight. Since the opening 244 is displaced from the powder inlet 200 of the primary hopper 60, the inside 203 of the housing can be accessed for maintenance or the like without interfering with the powder inlet 200. The first agitator 234 includes a motor 246 connected to the gear box 250 by a shaft 248. The output of gearbox 250 is drivingly connected to a shaft 252 housed in tube 254. Attached to the lower end of the shaft 252 are at least two stirrer paddles 256, which are inside the circular part 206 of the housing interior 203 formed by the inner wall 204, at a position vertically above the perforated plate 222. Rotate. Second agitator 236
Has a structure similar to that of the first agitator 234. 2nd stirrer 2
36 includes a motor 258 having a shaft 260 connected to a gear box 262, the output of the gear box drivingly connected to a shaft 264 housed in a tube 266. 2 or more paddles 268
The other circular portion of the housing interior 203 formed by the inner wall 204
Within 208, it is attached to the base of shaft 264. As shown in FIG. 4, the shaft 264 and tube 26 associated with the second agitator 246.
6 is slightly longer than that of the first agitator 234, so the second
The paddle 268 of the stirrer 236 is located closer to the perforated plate 222 than the first stirrer 234. Paddles 256 and 268 overlap, but they do not interfere with each other because they are vertically displaced.

As described above, one aspect of the present invention is, for example,
Transfer a large amount of powder coating material such as 136.2 kilograms (300 pounds) or more per hour at a flow rate of 0.454 to 0.908 kilograms (1 to 2 pounds) per second while achieving the desired density in the powder coating material flow. And maintaining particle distribution. As mentioned above, the term "density" refers to the relative mixing or proportion of powder and air, and the term "particle distribution" refers to powders of various sizes in a stream of powder coating material. Refers to the distribution of particles. Primary hopper 60 and recycle hopper 80 are designed to meet the desired density and particle distribution requirements for high throughput powder coating materials.

During operation, pressurized air is introduced into the perforated air tube 272 in the air plenum 230 to create an upward flow of air,
This is evenly distributed by the baffle 270 over the bottom of the perforated plate 22. The powder coating material is introduced into the housing interior 203 through the powder inlet 20 and is perforated by the upward flow of air for fluidization and by the action of the first and second agitators 234, 236. Distributed along 222. Stirrer paddle 25
As the 6 and 268 move relative to the perforated plate 222, the "8" shape of the housing interior 203 defined by the inner wall 204
Since the internal "dead point" is almost eliminated, the powder coating material is evenly distributed along the entire surface of the perforated plate 222, and the aggregation or accumulation of the powder material is almost eliminated. As a result, the powder is uniformly distributed in the fluidized bed 226, and the desired particle distribution and density are obtained. When the second vacuum pump 69 is activated,
The powder coating material mixed in the air is the housing of the primary hopper 60.
Suction tube sucked from 202 and inserted into the inside 203 of the housing
The inside of the housing passes through 274 and is connected to the transfer line 64 described above.

Feed Hopper Since the first and second feed hoppers 68 and 96 are basically of the same construction, only the first feed hopper 68 will be discussed in detail here. Referring to FIG. 5, the feed hopper 68 includes a top wall 278 formed with an opening closed by a cover 279, a generally cylindrical side wall 280, and a load cell.
And a bottom wall 282 carried by 106B. The housing 276 basically defines an interior that is separated into three distinct areas. One area is a fluidized bed 284 extending outwardly from the housing side wall 280 and between a perforated plate 286 supported on the side wall by brackets 288 and a top wall 278. A second area within the housing 276 is an air plenum 290 extending between a circular mounting plate 292 carried by a bracket 294 mounted on the sidewall 280 and a perforated plate 286. A third area inside housing 276 is a motor chamber 296 that extends between mounting plate 2292 and bottom wall 282.

The supply hopper 68 is provided with an agitator 298 including a motor 300 carried within a motor chamber 296 by a motor mount 302 connected to a mounting plate 292. The output of the motor 300 is drivingly connected to a shaft 304 rotatably carried in a bearing 306. Bearing 306 is a bearing mount
Attached to mounting plate 292 by 308, air plenum
It extends vertically upward through 290 to a point just above perforated plate 286. At least two paddles 308 are secured to the top of shaft 304 extending through bearings 206 by lock nuts 310 so that in response to motor 300 movement, paddle 308 is positioned directly above active plate 286. Rotate at the position.

At least two air inlets 312 are carried in the mounting plate 292 and are connected by a tube 314 to an air supply line 316 entering one side of the motor chamber 296 in a manner not shown. This air supply line 316 is connected to the pressurized air supply source 73 described above with respect to the powder receiver. An upward air flow is provided to the air plenum 290 through the air inlet 313, where the air is deflected by baffles 318 mounted on bearings 306. This baffle 318 is a powder receiver
The same type used for the 600 is disclosed in the aforementioned US Pat. No. 5,018,909.

In operation, powder coating material is introduced into the fluidized bed 284 of the enclosure 276 through a tapered powder inlet 276 mounted along the sidewall 280 of the enclosure 276. The motor 300 operates to rotate the paddle 308, so that the powder coating material is evenly distributed along the perforated plate 286 without a dead center. The powder coating material is
The upward air flow from the air supply line 316 and the air inlet 312 fluidizes along the perforated plate 286.
Pump 74 to remove powder coating material from enclosure 276.
The powder coating material is sucked through a suction pipe 322 extending into the inside of the casing just above the perforated plate 286 by operating one or more powder pumps. Several suction tubes 322 are shown in FIG. 5 to illustrate that multiple powder pumps 74 can be used to pump powder from the feed hopper 68.

Robot Hopper The robot hopper 78 shown schematically in FIG.
For more details. In a preferred embodiment of the invention,
The robot hopper 78 mixes 324 a motor chamber containing a motor 326 drivingly connected to a shaft 328 having one or more paddles 330 mounted on its upper end.
Including a cylindrical base forming. Robot hopper 78
The top of the air plenum and motor chamber 324
Bottom wall formed by perforated plate 336 and upper end 334
And a cylindrical housing 332 having. Cylindrical housing 332
Defines a fluidized bed 338 having a rectangular plate or baffle 340 mounted therein. Baffles 340 are vertically spaced above the perforated plate 336 and divide the fluidized bed 338 into two compartments. On one side or side of the baffle 340, the powder coating material from the feed hopper 68 has a cylindrical housing.
It is introduced through a powder inlet 342, which is shown schematically at the top of 332. Suction tube 344 associated with powder pump 79
Is attached to the cylindrical housing 332 opposite the baffle 340, the suction tube 344 ending just above the perforated plate 336.

Robot hopper 78 receives powder coating material via line 76 from powder pump 74 associated with supply hopper 68. The powder coating material enters the powder inlet 342 of the cylindrical housing 332, moves downward along one side of the baffle 340, and reaches the perforated plate 336. Since the motor 326 operates to rotate the paddle 330 just above the perforated plate 336, a uniform flow of the powder material mixed in the air is drawn out from the powder pump 79 through the suction pipe 344, and the robot moves. 40 and its associated spray gun 42. Cylindrical housing 332
A baffle 340 inside the powder pump helps stabilize the fluidization of the powder coating material across the perforated plate 336 and helps the powder pump
The flow of powder coating material drawn by 29 ensures that the desired density and powder distribution is maintained.

Powder Collection and Recovery System Referring to FIGS. 1 and 7-9, the powder collection and recovery system 16 is illustrated in further detail. This system 16 is generally referred to as Shutic et al.
Related to the system disclosed in 5,078,084, the disclosure of which is incorporated herein by reference in its entirety. As mentioned above, the powder collection and recovery system 16 is located below the floor 20 of the powder spray booth 12 on either side of the central portion 36 of the booth 12 where the carbody 32 is transported by the conveyor 34. As shown in the left-hand portion of FIG. 7, the grate 38 covers the booth floor 20 so that excess sprayed aerated powder coating material is directed downward into the system 16 from any area within the booth chamber 30. Can be sucked into.

The powder collecting and collecting apparatus 16 has a modular structure, and as a whole, includes a series of powder collecting units 346 which are vertically arranged along the entire length of the booth 12 and are mounted side by side. See center of FIG. As shown on the right side of FIGS. 1 and 4, the powder collection units 346 are connected to individual fan or blower units 348 located below the powder collection units 346, for example in groups of three or four. Each powder collection unit 346 includes a collector housing 350 having opposed side walls 354, 356, opposed end walls 358, 360, and an inclined bottom wall 362. A clean air chamber 364 is located at the top of the collector housing 350 and has a pair of support plates 336, 367 that slope inwardly and each has several spaced openings 368, opposite side plates 369, 390, and a pair of access doors 371, 372 hinged to side plates 369, 370, respectively. The clean air chamber 364 extends the length of the collector housing 350 and connects to the extension 373, the purpose of which is described below. The lower portion of the collector housing 350 has a powder collection chamber 374 having a bottom wall and a tapered sidewall defined by a perforated plate 376.
To form. The perforated plate 376 is the base 362 of the collector housing 350.
At an angle of about 5 degrees to the horizontal, forming an air plenum 377 therebetween. An upward airflow is introduced into the air plenum 377 below the perforated plate 376 through an inlet (not shown) so that the powder collection chamber 374
The incoming powder coating material fluidizes at the top of perforated plate 376.

In the preferred embodiment of the present invention, two groups or rows of cartridge filters 378 are located within the powder collection chamber 374 and are arranged in an inverted V shape, as seen in FIG. The open top of each cartridge filter 378 is connected to the support plates 366, 36 of the clean air chamber 364.
It is carried by one of the plates 7 above the opening 368 of the plates 366, 367. Each cartridge filter 378 has a center rod 382 threaded at the top and receives a mount 384 that is clamped to the rod 382 so that one of the support plates 366 or 367 connects the mount 384 and the top of the cartridge filter 378. Sandwiched between. One or more of the filter mounting plates 386 extending between the end walls 358, 360 of the collector housing 350 preferably provide additional support for each cartridge filter 378.

In order to remove the powder coating material that enters the collector housing 350 from the walls of the cartridge filter 378 as discussed above, each bank of the cartridge filter 378 has:
One set or group of air jet nozzles 392 are provided. A set of air jet nozzles 392 is carried on a nozzle support 394 mounted in a clean air chamber 364 and a second set of air jet nozzles 392 is in the clean air chamber 364. Supported on the nozzle support 396 of FIG. As shown in FIG. 8, each set of air jet nozzles 392 is directed to the open top of a group or row of cartridge filters 378. The air jet nozzle 392 associated with each row of cartridge filters 378 is connected to the air line 3
It is connected by 98 to a hydraulic valve 400, which is connected to a pressurized air supply 73. In response to a signal from system controller 108, hydraulic valve 400 is actuated to cause a jet of pressurized air to be expelled from air jet nozzle 392 to one or both rows of cartridge filters 378. Selectively direct pressurized air through 398. This pulsed air jet removes the powder coating material from the walls of the cartridge filter 378 so that the powder coating material can fall by gravity into the powder collection chamber 374 and further to the perforated plate 376. .

With reference to FIGS. 1 and 7, the airborne powder coating material is drawn into each of the powder collection units 346 from the booth interior 30 when subjected to the negative pressure generated by the blower unit 348 described above. Each blower unit 3
48 includes a fan plenum 402 that houses a fan or blower 404, and some final filters 406 shown schematically in FIG. The fan plenum 402 is formed with a number of openings 408 on which the exhaust duct 410 is fixed. Each exhaust duct 410 extends vertically upward to engage a shaft coupling 412 located at the base of one of the clean air chambers 364 associated with each powder collection unit 346.
In response to the operation of the blower 404 in the fan plenum 402, a negative pressure is generated in the exhaust duct 410, and each powder collection unit 3
It also creates in the clean air chamber 364 associated with 46. This negative pressure causes a downward air flow in the booth chamber 30, to which powder coating material excessively sprayed is mixed. The powder coating material entrained in the air passes through the grid 38 on the floor 20 of the spray booth 12 into each powder collection unit 346, where the powder coating material
It collects along the walls of the filter 378 or falls onto the perforated plate 376 at the base of the collector housing 350.

The important aspects of the powder collecting and collecting system 16 of the present invention are:
One blower unit 348 is to accommodate a limited number of powder collection units 346. For example, the blower unit 348A shown on the right side of FIG.
Fan plenum 4 formed with four openings 408 that receive an exhaust duct 410 connected to one powder collection unit 346
Have 02. Therefore, four powder collection units 346
One blower unit 348A supports. The other blower unit 348 is associated with a relatively small group of adjacent powder collection units 346, so that
A uniform downward airflow is provided throughout the booth chamber 30. In addition, the configuration of the clean air chamber extension 373 of each powder collection unit 346 allows the spray base 1
The powder collection unit 346 on one side of the 2 can be “doweled” or fitted to the powder collection unit 346 on the other side of the booth 12. See center of FIG. This saves space and reduces the overall size of booth 12.

Another aspect of the powder collection and collection system 16 of the present invention is to collect the collected oversprayed powder from the powder collection unit 346 and recycle it back to the powder kitchen 14. As described above, the powder material mixed in the air from the booth chamber 30 is sucked into each powder collecting unit 346 and dropped by gravity onto the perforated plate 376 at the base or the air jet nozzle 392. It is removed from the wall of the cartridge filter 378 by a periodic jet of pressurized air released from the. In a preferred embodiment of the invention, the movement of the powder to the perforated plate 376 is such that the collector of each powder collection unit is vibrated when an opposite pressurized air jet is emitted from the air jet nozzle 293. It is aided by forming the walls 354-362 of the housing 350 with a relatively thin metal such as 18-20 gauge No. 304 stainless steel. Perforated plate 37
Since 6 has an angle of about 5 degrees with respect to the horizontal, the fluidized powder coating material on it is directed toward the outlet 422 on one side of the collector housing 350 at the lower end of the perforated plate 376. Flowing. Each outlet 422 of the powder collection unit 346 has a branch line 42
Connected by 4 to a common header pipe 426, which extends longitudinally along the length of the powder booth 12 on either side thereof. The header pipe 426 is connected to a regeneration line 86 that connects to a third powder receiver 82 within the powder kitchen 14. A guillotine-type gate valve 428 is preferably carried in each branch line 424, the valve being movable between an open position in which the powder coating material can flow and a closed position in which such flow is impeded.

The third vacuum pump 84 in the powder kitchen 14 is associated with the third powder receiver 82 and the recycle hopper 80 as described above, but in response to this activation, a negative pressure is created in the header pipe 426. . The system controller 108 described above in connection with the powder transfer system operates to activate each powder collection unit 3
The gate valve 428 associated with 46 is selectively opened so that powder therein is sucked into header pipe 426 through respective branch lines 424. Due to the large number of powder collection units 346, only a certain number of gate valves 428 will be open at a given time for transfer to the recycle line 86 leading to the third powder receiver 82 and primary hopper 80. Limit the total amount of powder material that can enter the header pipe 426.

Referring to FIG. 1, a pressure sensor 430 is schematically illustrated as connected to a fan plenum 402 of a blower unit 348. The purpose of the pressure sensor 430 is to sense the pressure drop across the final filter 406 within the blower unit 348 and send a signal representative thereof to the controller 108. If one or more of the cartridge filters 348 fails or has other problems within the powder collection unit 346 associated with a given blower unit 348, the powder coating material will cause the clean air chamber 364 to run. Pass by
The final filter 406 is reached and the pressure drops in the final filter 406. This pressure drop is sensed by pressure sensor 430, at which time a signal representative of such a pressure drop is sent to controller 108 to alert the operator that there is a problem within such powder collection unit 346. To do. Since there are several blower units 346, it is possible to pinpoint a failure in the powder collection and recovery system 16 and
It can be attributed to a group of 348 and associated powder collection units 346. This facilitates system maintenance and does not require the operator to inspect each of the blower units 348 when such problems arise.

Although the present invention has been described in relation to the preferred embodiments, those skilled in the art can, without departing from the scope of the invention,
It is understood that various changes can be made to the element and that it can be replaced with the equivalent. Also, many modifications may be made to a particular situation or material to the teachings of the invention without departing from the basic scope of the invention.

For example, the system 10 of the present invention includes a single primary hopper 60, a single recycle hopper 80, a feed hopper 68 associated with a robot hopper and robot 40, and a feed hopper associated with an overhead gun manipulator 44. I have said that there are 96. The embodiments of the system 10 shown in the drawings and described above are intended to illustrate the subject matter of the invention, it being understood that the system 10 may be modified according to the requirements of a particular application. Multiple primary hoppers 60
And recycle hopper 80 can be used to provide a variety of spray hoppers including various combinations of feed hoppers and automatic and manual guns fed by robot hoppers.
Gun configurations can be used.

Accordingly, the invention is not limited to the particular embodiments disclosed as the best mode contemplated for carrying out the invention, but the invention includes all embodiments falling within the scope of the appended claims. And

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Holstein, Thomas, E. USA. 44001 Ohio, Amherst, Forest Hill Drive 104 (72) Inventor Williams, Keith, E. USA. 48158 Michigan, Manchester, Sharon Valley Road 19190 (72) Inventor Fuena, Ernest, J. USA. 44116 Ohio, Rocky River, Locust Lane 22577 (72) Inventor Ladder, Harley J. USA. 44107 Ohio, Lakewood, Woodward Avenue 2379 (56) References JP-A-61-212354 (JP, A) US Patent 4373820 (US, A) US Patent 3791341 (US, A) (58) Research Fields ( Int.Cl. ⁷ , DB name) B05B 15/00-15/12 B05B 7/14

Claims (36)

(57) [Claims] 1. A powder coating system comprising: an unused powder hopper containing an unused powder coating material; and a first powder weight or volume measuring device associated with the unused powder hopper. Communicating with the powder spray booth so that oversprayed powder coating material that did not adhere to objects moving through the powder spray booth can be received from the powder spray booth A regenerated powder hopper, a second powder weight or volume measuring device associated with the regenerated powder hopper, the unused powder hopper and the regenerated powder hopper, and the powder Utilizing the information received from the mixing hopper in communication with at least one paint dispenser associated with the spray booth and the information received from the first and second measuring devices,
From the unused powder hopper and the regenerated powder hopper, respectively, each of the unused powder coating material and the excessively sprayed powder coating material is supplied to the mixing hopper at a selected ratio, A powder coating system comprising: a controller unit for mixing and supplying to the at least one coating dispenser. 2. The powder coating system of claim 1, wherein the unused powder hopper is connected to at least one other coating dispenser associated with the powder spray booth. . 3. The particle size distribution of a mixture of an unused powder coating material and an excessively sprayed powder coating material in the mixing hopper is controlled by the controller unit from a particle size distribution measuring device. The powder coating system of claim 1, wherein the powder coating system is operative to receive a measured value of. 4. The controller unit calculates a total volume percentage of powder coating material in the mixing hopper having a particle size smaller than a selected minimum size, and the calculated total volume percentage is desired. The powder coating system of claim 3, wherein the powder coating system operates as compared to a total volume percentage. 5. The unused powder hopper is connected to the mixing hopper by at least one line carrying a first valve, and the regenerated powder hopper is at least one line carrying a second valve. Is connected to the mixing hopper by means of which the controller unit opens and closes the first and second valves to enter unused powder coating material and excess sprayed powder coating material entering the mixing hopper. The powder coating system of claim 1, wherein the powder coating system operates to control an amount. 6. The hopper casing having an inside including an inner wall forming a first powder fluidization region and a second powder fluidization region, and a perforated plate carried in the hopper casing. And the perforated plate divides the inside of the hopper casing to provide a fluidized bed on the perforated plate and air
A plenum is provided, and the hopper housing has a powder inlet for introducing a powder coating material into the fluidized bed and an air inlet for introducing an upward air flow into the air plenum below the perforated plate. Is formed, and comprises a first stirrer disposed in the first powder fluidization zone and a second stirrer disposed in the second powder fluidization zone, the first and second The powder coating system according to claim 1, wherein the agitator serves to generate a stable fluidized bed of powder in each of the first and second fluidization zones. 7. The inner wall of the hopper housing is formed into a generally figure-eight shape having two generally circular portions that meet at a central region of reduced diameter. Powder coating system. 8. The first and second stirrers each include a paddle disposed in the first and second powder fluidization zones on the perforated plate and driven by a motor, 7. The powder coating system according to claim 6, wherein one of the paddles is arranged so as to partially overlap vertically above the other paddle. 9. The first measuring device comprises a first load measuring device for measuring the weight of the powder coating material in the unused powder hopper.
2. The powder according to claim 1, wherein the powder is a cell, and the second measuring device is a second load cell for measuring the weight of the powder coating material in the regenerated powder hopper. Painting system. 10. In a powder coating material transferred from said virgin powder hopper and said regenerated powder hopper to said mixing hopper, a particle size smaller than the selected minimum size achieves the desired maximum amount. The powder coating system according to claim 1, wherein the selected ratio is set as described above. 11. The particle size distribution of a sample of unused powder is divided into a number of size ranges, and powder particles within the size range are sprayed from a coating dispenser for each size range. Later, by determining the probability coefficient that it remains in the oversprayed powder without sticking to the object to be coated, the amount of particle size smaller than the selected minimum size is determined, Predict the particle size distribution of the over-sprayed powder by multiplying the probability coefficient by the fresh particle size distribution, and the particle size distribution of the unused powder and the over-sprayed powder. Particle size distribution of the powder to the mixing hopper to achieve only the desired maximum amount of particle size less than the selected minimum size in the powder coating material transferred to the mixing hopper. Transferred Powder coating system according to claim 10, characterized in that it is used to set the percentage of unused powder against excessively sprayed was powder must. 12. For powders in the mixing hopper, the amount of particle size smaller than the selected minimum size is determined and compared to the maximum amount, and if the maximum amount is exceeded, 12. The powder of claim 11, wherein virgin powder coating material is transferred to the mixing hopper such that the amount of particle size less than the selected minimum size is less than the maximum amount. Body coating system. 13. The powder coating system of claim 1, wherein a third powder weight or volume measuring device is associated with the mixing hopper. 14. The powder coating according to claim 13, wherein the third measuring device is a third load cell for measuring the weight of the powder coating material in the mixing hopper. system. 15. The powder according to claim 14, wherein the powder is supplied from the mixing hopper to a first supply hopper and from the first supply hopper to a first set of coating dispensers. Powder coating system. 16. The powder coating system according to claim 15, wherein a fourth load cell is provided for measuring the weight of the powder in the first supply hopper. 17. The powder is supplied from the unused powder hopper to a second supply hopper, and from the second supply hopper to a second set of coating dispensers. The powder coating system described in. 18. The powder coating system according to claim 17, wherein a fifth load cell is provided for measuring the weight of the powder in the second supply hopper. 19. The powder coating system according to claim 15, wherein the powder is transferred from the mixing hopper to the first supply hopper by a vacuum pump. 20. The powder coating system according to claim 18, wherein powder is transferred from the unused powder hopper to the second supply hopper by a vacuum pump. 21. A method of applying a granular powder coating material to an object moving through a powder spray booth, the method comprising: Spraying the body coating material onto an object moving through the powder spray booth; and overspraying the powder coating material that did not adhere to the object in the powder spray booth. Transfer from the powder spray booth to the reclaimed powder hopper, mixing unused powder material from the unused powder hopper, and excess sprayed powder material from the reclaimed powder hopper And controlling the ratio of the unused powder material and the excessively sprayed powder material supplied from the unused powder hopper and the regenerated powder hopper to the mixing hopper. Smaller than the minimum size Ensuring that the amount of powder particles does not exceed a predetermined percentage of the total amount of powder coating material fed to the mixing hopper. 22. Measuring the particle size distribution of the powder coating material in the mixing hopper, and determining the percentage of powder particles smaller than the selected minimum particle size. Comparing said percentage to the desired percentage, and if said determined percentage is greater than said desired percentage, supply virgin powder material to said mixing hopper to select said selected hopper in said mixing hopper. Adjusting the percentage of powder particles smaller than the minimum particle size to be less than the desired percentage.
The method described in 21. 23. The particle size distribution of a sample of virgin powder is divided into a number of size ranges, and powder particles within the size range are sprayed from a coating dispenser for each size range. Afterwards, by determining the probability coefficient that the powder remains in the oversprayed powder without sticking to the objects in the powder spraying booth, a particle size of less than the selected minimum size is determined. An amount is determined to predict the particle size distribution of the oversprayed powder by multiplying the probability coefficient by the virgin particle size distribution,
Then, the particle size distribution of the unused powder and the particle size distribution of the regenerated powder are the desired particle sizes smaller than the selected minimum size in the powder coating material transferred to the mixing hopper. The ratio of virgin powder to oversprayed powder that must be transferred from the virgin powder hopper and the reclaimed powder hopper to the mixing hopper, respectively, to achieve only the maximum amount of 22. The method according to claim 21, characterized in that it is used for setting. 24. The step of further supplying powder from the mixing hopper to the first supply hopper, and from the first supply hopper to the first set of coating dispensers, and the second supply from the unused powder hopper. Supplying the powder to the hopper and from the second supply hopper to the second set of coating dispensers.
The method described in. 25. The powder is transferred from the mixing hopper to the first supply hopper by a vacuum pump, and the powder is
25. The method of claim 24, wherein the powder is transferred from the fresh powder hopper to the second feed hopper by a vacuum pump. 26. The first load cell measures the weight of the powder in the unused powder hopper, and the second load cell measures the weight of the powder in the regenerated powder hopper. The first and second load cells transfer the desired proportion of fresh and oversprayed powder from the fresh powder hopper and the reclaimed powder hopper to the mixing hopper. 22. The method of claim 21, wherein the method is used to: 27. The method of claim 26, wherein the third load cell weighs the powder in the mixing hopper. 28. The ratio of the unused powder material to the excessively sprayed powder coating material is such that 70% of the powder supplied to the mixing hopper becomes the unused powder, and the powder is supplied to the mixing hopper. 22. The method of claim 21, wherein 30% of the powder is controlled to be oversprayed powder. 29. The powder spray booth includes a plurality of overspray powder recovery hoppers, and the regenerated powder hopper receives excess sprayed powder from the powder recovery hoppers. The powder coating system according to claim 1, wherein: 30. Each of the recovery hoppers includes a powder recovery chamber, each of the powder recovery chambers receiving excess sprayed powder coating material from the powder spray booth. Includes a perforated plate attached to a predetermined position at a predetermined angle with respect to the horizontal direction at the bottom of the powder recovery chamber, and the powder recovery chamber includes powder received by the perforated plate. 30. The powder coating system of claim 29, wherein an air inlet is formed for passing a stream of air through the perforated plate to fluidize the body coating material. 31. Each of the perforated plates has a lower end, and an outlet from each of the powder recovery chambers is provided at the lower end of the perforated plate, and each of the outlets. 31. The powder coating system according to claim 30, wherein the powder coating system communicates with the regenerated powder hopper and supplies excessively sprayed powder from the powder recovery chamber to the regenerated powder hopper. . 32. A valve is provided at each outlet of the powder recovery chamber, and the controller unit selectively opens the valve to remove excess sprayed powder from the powder. 32. The powder coating system according to claim 31, wherein the powder coating system transfers the powder from each of the body recovery chambers to the regenerated powder hopper. 33. The powder coating system according to claim 32, wherein a vacuum pump is used to transfer the powder from the powder recovery chamber to the regenerated powder hopper by suction. 34. Each of said recovery hoppers comprises a plurality of cartridge filters, wherein excess powder sprayed is recovered on said cartridge filters and later transferred to a regenerated powder hopper. Claims to be characterized
29. The powder coating system described in 29. 35. The powder coating according to claim 34, wherein the plurality of cartridge filters of the recovery hopper are arranged in two rows in an inverted V shape in the powder recovery chamber. system. 36. Further comprising a plurality of reverse air jet valves mounted in place on the cartridge filters, each of the reverse air jet valves being aligned with each of the cartridge filters. 36. The powder coating system according to claim 35, characterized in that it is arranged.