阅读说明：本技术 涂覆室 (Coating chamber ) 是由 亨利·马孔 于 2019-02-18 设计创作，主要内容包括：一种用于要涂覆的元件的涂覆室(101)。涂覆室(101)包括在相对的竖直侧面(107a,107b,108a,108b)之间的通路,要涂覆的元件被输送通过该通路。在通路的一个端部处存在入口(105),在通路的另一个端部处存在出口(106)。涂覆室(101)包括：输送线(102),所述输送线用于支撑所述要涂覆的元件并且被配置为沿着直路径将这些元件从入口(105)输送到出口(106)；以及抽吸系统。该通道的相对侧是关于该路径对称的。用于向元件喷涂涂料粉末的喷枪组(103a,104a,103b,104b)对称地设置在直路径的两侧。抽吸系统包括彼此相对安装在通路的每个相对竖直侧面上的竖直抽吸入口(109a,109b),该抽吸系统被配置为通过每个相对的竖直抽吸入口(109a,109b)提供相等量的抽吸。(A coating chamber (101) for an element to be coated. The coating chamber (101) comprises a passage between opposite vertical sides (107a, 107b, 108a, 108b) through which the element to be coated is conveyed. There is an inlet (105) at one end of the passageway and an outlet (106) at the other end of the passageway. The coating chamber (101) comprises: a conveyor line (102) for supporting the elements to be coated and configured to convey these elements along a straight path from an inlet (105) to an outlet (106); and a suction system. The opposite sides of the channel are symmetrical about the path. Groups of spray guns (103a, 104a, 103b, 104b) for spraying coating powder to the components are symmetrically arranged on both sides of the straight path. The suction system comprises vertical suction inlets (109a, 109b) mounted opposite each other on each opposite vertical side of the passageway, the suction system being configured to provide an equal amount of suction through each opposite vertical suction inlet (109a, 109 b).)

1. A coating chamber for an element to be coated, the coating chamber comprising: a passageway between opposite vertical sides through which the element to be coated is conveyed; an inlet at one end of the passageway; and an outlet at the other end of the passageway;

a conveyor line for supporting the elements to be coated and configured to convey the elements along a straight path from the inlet to the outlet; and

a suction system is arranged on the air-conditioning system,

wherein:

the opposite sides of the channel are symmetrical about the path;

a pair of spray guns for spraying coating powder to the components are symmetrically arranged on both sides of the straight path; and

the suction system includes vertical suction inlets mounted opposite one another on each opposing vertical side of the passageway, the suction system being configured to provide an equal amount of suction through each of the opposing vertical suction inlets.

2. The coating chamber of claim 1 wherein each vertical suction inlet extends substantially along the entire height of the chamber.

3. Coating booth according to any one of the preceding claims, comprising a system for hooking the elements to be coated onto the conveyor line, said hooking system being configured for horizontal translation and suspended conveyance of the elements to be coated in vertical position.

4. The coating booth according to any one of the preceding claims, wherein said spray gun group has a reciprocating and controlled movement along a vertical axis, so that it can be configured to spray said coating powder along the entire height range of said element to be coated.

5. The coating chamber of any one of the preceding claims wherein said suction system is configured to generate an air flow in said passageway that is substantially symmetrical about said path.

6. The coating chamber of any one of the preceding claims, wherein each vertical suction inlet is divided into an upper portion and a lower portion on both sides of a suction source, each vertical suction inlet further comprising one or more movable baffles configured to divert an amount of suction force from the suction source to the upper portion or the lower portion of each vertical suction inlet.

7. The coating chamber of claim 6, wherein the outer and inner walls of the chamber that define the sides of the channel comprise a cross-sectional closed sheet of flexible material that is inserted over and held in tension by a motorized rotatable roller that rotates the sheet past a cleaning device, wherein the cleaning device is configured to remove excess coating powder deposited on the flexible material.

8. The coating booth of claim 7, wherein each side of said channel comprises two sheets of flexible material extending substantially along the height of said spray booth, and wherein each vertical suction inlet is disposed between said two sheets of flexible material on each side of said booth.

9. The coating booth of claim 8, wherein said rotatable roller is configured to rotate when said spray gun is positioned to spray powder onto portions of said element that are lateral to a lower portion of said suction inlet and when substantially all of the suction force is diverted to said lower portion of said vertical suction inlet.

10. The coating chamber according to any of the preceding claims, wherein each opposing vertical side of the channel is longitudinally straight and parallel to the path.

11. The coating chamber according to any of the preceding claims, wherein the spray gun groups comprise a first spray gun group located near the inlet and a second spray gun group located near the outlet.

12. The coating chamber according to any one of the preceding claims, further comprising a cleaning tank having an open top configured to receive any of the spray gun groups, wherein:

the spray gun groups each being operable to rotate to a downward position for insertion of a nozzle of the spray gun group into the cleaning bin; and is

The cleaning tank is configured to provide a stream of air directed toward the inserted nozzles of the spray gun stack to clean the nozzles.

13. A method of coating a component in a coating chamber, the method comprising the steps of:

passing a component to be coated through a passageway between opposite vertical sides from an inlet at one end of the passageway to an outlet at the other end of the passageway, the component being conveyed along a straight path along a conveyor line, wherein opposite sides of the channel are symmetrical about the path;

operating groups of spray guns to spray coating powder onto the component, the groups of spray guns being symmetrically disposed on either side of the straight path;

operating a suction system comprising vertical suction inlets mounted opposite one another on each of the opposite vertical sides of the passageway, the suction system for providing an equal amount of suction through each of the opposite vertical suction inlets.

14. The method of claim 13, wherein the element to be coated is suspended in a vertical position.

15. The method of claim 13 or 14, further comprising the step of moving the electrostatic spray gun stack along a vertical axis to spray powder coating along any portion of the height of the element to be coated.

16. The method of any one of claims 13 to 15, wherein the suction system generates a substantially symmetrical air flow in the passageway about the path.

17. The method of any one of claims 13 to 16, wherein each vertical suction inlet is divided into an upper portion and a lower portion on either side of a suction source, and further comprising the step of moving one or more baffles of each vertical suction inlet to divert an amount of suction from the suction source to the upper portion or the lower portion of the vertical suction inlet.

18. The method of claim 17, wherein the outer and inner walls of the chamber that define the sides of the channel comprise a cross-sectional closed sheet of flexible material that is inserted on a motorized rotatable roller and held in tension by the motorized rotatable roller, the method further comprising the step of rotating the sheet past a cleaning device, wherein the cleaning device is configured to remove excess coating powder deposited on the flexible material.

19. The method of claim 18, further comprising the step of rotating the rotatable roller when the spray gun is positioned to spray powder onto portions of the element that are lateral to the lower portion of the vertical suction inlet and when substantially all available suction is diverted to the lower portion of the vertical suction inlet.

20. The method of any one of claims 13 to 19, further comprising the step of rotating the spray guns to a downward position for inserting nozzles of each spray gun group into a cleaning tank and cleaning the inserted nozzles of the spray gun groups by directing air jets towards the inserted nozzles within the cleaning tank.

Technical Field

The present invention relates to a coating booth for coating elongated elements, such as extruded sections suspended in a vertical position on an overhead conveyor line.

Introduction to the design reside in

Coating chambers in continuous coating systems are used to coat components on a conveyor line. Typically, these components are translated through a coating booth where they are sprayed with coating powder by an electrostatic spray gun. Due to electrostatic action, the coating powder adheres to the surface of the element to be coated.

EP 2897740B 1 discusses that at present the coating booth is generally in the shape of a parallelepiped-shaped tunnel closed at the sides, bottom and top. Overhead conveyor lines pass through both open surfaces at the tunnel entrance and exit. The elements to be coated are suspended on a conveyor line and exposed to the spray of an electrostatic spray gun within the coating chamber. Suction inlets at the sides and top are used to extract powder not deposited on the component.

Such a chamber has several disadvantages. For example, the resulting coating may be of poor quality due to variations in the thickness of the resulting coating resulting from uneven distribution of the powder in the chamber. In elements with complex cross-sections there is the problem of powder penetration into the grooves of the profile. Such chambers are also inefficient because a large amount of powder is not deposited on the elements and remains suspended in the air or on the inner surfaces of the chamber, thereby requiring complex and unsanitary cleaning methods. Another problem is that these elements are susceptible to undesirable oscillatory motion due to air flow and inertial forces, which can reduce the quality of the resulting coating.

EP 2897740B 1 proposes a coating chamber that overcomes some of these disadvantages. The proposed chamber has a triangular plane schematically identified by three sides. The elements enter and exit the chamber via one side (i.e. take a curved or angled route through the chamber). The remaining two sides intersect the vertical suction inlet. One of the two sets of lances is provided at each of a point at which the element enters the chamber and a point at which it exits the chamber. The entry point and the lance at the entry point are in the direction of travel of the element or in the opposite direction of travel of the element, respectively. In this way, an air flow is provided for pushing the powder past the element and into the suction inlet.

Additionally, each of the two sides intersecting the vertical suction inlet comprises a "conveyor belt" wall that transfers powder deposited on the wall to a scraper that removes such deposited powder.

The chamber of EP 2897740B 1 has several disadvantages. The chamber requires a bend/angle in the conveyor line. This creates a risk of undesired inertial movements of the element as it travels around the bend. This problem is exacerbated when the component to be coated is large. Furthermore, the width of the element compatible with this chamber is limited by the relatively narrow geometry. This is clearly seen in the diagram of EP 2897740B 1. Furthermore, when only one set of spray guns is spraying, the flow pattern within the chamber is asymmetric, which may result in an uneven coating distribution.

The present invention is directed to overcoming the disadvantages of existing spray booths.

It is also desirable to provide a paint spray booth having a more efficient suction system than existing paint spray booths.

Disclosure of Invention

According to a first aspect of the invention, a coating chamber for an element to be coated is provided. The coating chamber comprises a passage between opposite vertical sides through which the elements to be coated are conveyed. There is an inlet at one end of the passageway and an outlet at the other end of the passageway. The coating chamber further comprises: a conveyor line for supporting the elements to be coated and configured to convey them along a straight path from an inlet to an outlet; and a suction system. The opposite sides of the channel are symmetrical about the path. The groups of spray guns for spraying the coating powder to the elements are arranged symmetrically on both sides of the straight path. The suction system includes vertical suction inlets mounted opposite one another on each of the opposite vertical sides of the passageway, the suction system being configured to provide an equal amount of suction through each of the opposite vertical suction inlets.

The use of a passageway having an inlet and an outlet at each end allows the element to pass through the spray booth without the size constraints imposed by the curvature of the delivery path. Furthermore, it is only necessary to make the width of the chamber similar to the width of the element to be coated. In contrast, a triangular spray booth must be wide enough to include an inlet and an outlet on one side of the booth (thus, similar in width to the width of two elements side-by-side).

The use of a straight conveyor line (along a straight path) reduces the amount of inertial motion introduced into the elements to be coated as they move along the conveyor line, particularly when the elements are pivotally suspended. In particular, the inertial motion in the direction perpendicular to the direction of motion is reduced. This is in contrast to alternative chambers that incorporate a "V" shaped conveyor line, where this inertial motion occurs as the orientation of the components changes.

Suction is provided to extract any excess coating powder that does not adhere to the component to be coated. The suction system reduces the amount of coating powder particles that are either suspended in the coating chamber, are floated out of the coating chamber, or are attached to the walls of the coating chamber. Providing equal levels of suction on each side of the channel helps to reduce the movement of the element to be conveyed, since the element is not pulled in either direction by the air flow in the chamber. The equal level of suction also helps to ensure that the powder is equally distributed over the elements as they pass through the chamber.

Optionally, each vertical suction inlet extends substantially along the entire height of the chamber.

Optionally, the coating booth comprises a system for hooking the elements to be coated onto the conveyor line, configured for horizontal translation and suspended conveyance of the elements to be coated in vertical position.

Optionally, the spray gun group has a reciprocating and controlled movement along a vertical axis, so that the spray gun group can be configured to spray coating powder along the entire height range of the element to be coated.

Optionally, the suction system is configured to generate an air flow in the passageway that is substantially symmetrical about the path.

The symmetrical air flow distributes the powder particles more evenly around the element to be coated.

Optionally, each vertical suction inlet is divided into an upper portion and a lower portion on either side of the suction source, each vertical suction inlet further comprising one or more movable baffles configured to divert an amount of suction from the suction source to either the upper portion or the lower portion of each vertical suction inlet.

The movable baffle diverts the suction force to a particularly vertically defined portion of the chamber. This ensures efficient use of the suction force obtained from the suction source. For example, when the top portion of the element is coated, a high suction force needs to be generated at the corresponding top portion of the chamber. In this case, little or no suction is provided at the bottom portion of the chamber. Diverting the suction force to the relevant lateral portion of the chamber improves the efficiency of the suction system by avoiding unnecessary suction forces being applied to unwanted portions of the chamber.

Another advantage is that the required suction force is reduced. Thus, components and systems (such as filters and motors) that may be present downstream of the suction inlet may be smaller and require less energy.

Optionally, the outer and inner walls of the chamber defining the sides of the channel comprise a closed sheet of flexible material in cross-section inserted on and held in tension by a motorized rotatable roller that rotates the sheet past a cleaning device, wherein the cleaning device is configured to remove excess coating powder deposited on the flexible material.

The cleaning device may include a cleaning system. The cleaning system may include a scraper configured to scrape powder from the flexible material.

Optionally, each side of the channel comprises two sheets of flexible material extending substantially along the height of the spray booth, and wherein each vertical suction inlet is provided between the two sheets of flexible material on each side.

This arrangement of each vertical suction inlet causes excess powder to be drawn towards one of the sheets of flexible material rotating through the cleaning device.

Optionally, the rotatable roller is configured to rotate when the spray gun is arranged to spray powder onto a portion of the element that is lateral to the lower portion of the vertical suction inlet and when substantially all available suction is diverted to the lower portion of the vertical suction inlet.

It has been found that engaging the rollers only in this manner makes the cleaning device more efficient.

Optionally, each opposing vertical side of the channel is longitudinally straight and parallel to the path.

Optionally, the groups of lances include a first group of lances located adjacent the inlet and a second group of lances located adjacent the outlet.

Optionally, the spray booth further comprises a clean box having an open top configured to receive any of the spray gun groups, wherein the spray gun groups are each operable to rotate to a downward position for inserting the nozzles of the spray gun groups into the clean box. The cleaning tank may be configured to provide a stream of air directed toward the inserted nozzles of the spray gun groups to clean the nozzles.

This provides for automatic cleaning of the nozzle, for example when the colour of the coating powder is to be changed. Thus, the risk of powder contamination due to coating powder of a previous color that may have been deposited on the nozzle surface is reduced.

According to a second aspect of the invention, there is provided a method of coating a component in a coating chamber, the method comprising the steps of:

-elements to be coated are transported through a passage between opposite vertical sides from an inlet at one end of the passage to an outlet at the other end of the passage, the elements being transported along a straight path along a transport line, wherein opposite sides of the channel are symmetrical about the path;

-operating groups of spray guns to spray paint powder onto the component, the groups of spray guns being symmetrically arranged on both sides of the straight path;

-operating a suction system comprising vertical suction inlets mounted opposite each other on each opposite vertical side of the passageway, the suction system for providing an equal amount of suction through each opposite vertical suction inlet.

Optionally, the element to be coated is suspended in a vertical position.

Optionally, the method further comprises the step of moving the set of electrostatic spray guns along the vertical axis to spray the powder coating along any portion of the height of the element to be coated.

Optionally, the suction system generates a substantially symmetrical air flow in the passage about the path.

Optionally, each vertical suction inlet is divided into an upper portion and a lower portion on either side of the suction source, and further comprising the step of moving the one or more baffles of each vertical suction inlet to adjust the amount of suction force applied from the suction source to the upper portion or the lower portion.

Optionally, the outer and inner walls of the chamber defining the sides of the channel comprise a cross-sectional closed sheet of flexible material inserted on and held in tension by a motorized rotatable roller, the method further comprising the step of rotating the sheets past a cleaning device, wherein the cleaning device is configured to remove excess coating powder deposited on the flexible material.

Optionally, the method further comprises the step of rotating the rotatable rollers when the spray gun is arranged to spray powder onto a portion of the element that is lateral to one of the upper and lower portions of the suction inlet.

Optionally, the method further comprises the step of rotating the spray guns to a downward position for inserting the nozzles of each spray gun group into the cleaning tank and cleaning the inserted nozzles by directing a stream of air towards the inserted nozzles within the cleaning tank to clean the nozzles of the spray gun groups.

Drawings

FIG. 1 is a schematic plan view of a paint spray booth according to an embodiment of the present invention.

Fig. 2 is a longitudinal side view of the spray booth of fig. 1.

Fig. 3 is a side elevational view of the spray booth of fig. 1 and 2.

Fig. 4 is an isometric view of the spray booth of fig. 1-3.

Fig. 5 is an isometric cross-sectional view of a baffle for adjusting the suction force applied to the upper or lower portion of the vertical suction inlet of the spray booth according to fig. 1 to 4.

Fig. 6 is a close-up view of one end of a flexible sheet mounted on rotatable rollers defining sides of a chamber of a cleaning device including the spray booth of fig. 1-4.

Fig. 7 is a close-up isometric view of a set of spray guns of a spray booth according to an embodiment of the present invention.

Figures 8a to 8c are isometric views of a set of spray guns and associated cleaning tanks in different stages of a nozzle cleaning operation according to an embodiment of the invention.

Detailed Description

Referring to fig. 1, there is a coating chamber 101 for receiving and coating a component (not shown) to be coated. The delivery line 102 enters the coating chamber 101 at a chamber inlet 105 and exits the coating chamber 101 at a chamber outlet 106. The transfer line 102 is straight while it is in the coating chamber 101. Arrow 114 indicates the direction of movement of components (not shown) along the transport line 102.

The sides of the chamber 101 are defined by walls 107a, 107b on one side and walls 108a, 108b on the other side. The sides are symmetrical about a path formed by the portion of the delivery line 102 within the chamber 101.

Vertical suction inlets 109a, 109b are located between walls 107a, 108a and walls 107b, 108b, respectively. The suction inlets are symmetrical to each other about the conveying line 102. The vertical suction inlets 109a, 109b face the chamber 101 for sucking air and suspended excess powder particles out of the chamber 101. In the illustrated embodiment, the vertical suction inlets 109a, 109b are connected to the cyclonic suction system 110a, 110b via ducts 111a, 111 b. It will be appreciated that any known suction system may be used to provide suction power to the vertical suction inlets 109a, 109 b.

On one side of the feed line 102, gun groups 103a, 104a are mounted. The opposing groups 103b, 104b of lances are mounted symmetrically with respect to the feed line 102 from the groups 103a, 104a of lances. In the illustrated embodiment, the lances 103a, 103b are mounted adjacent the inlet 105 and are angled towards the direction of movement of the feed line 102. The lances 104a and 104b are mounted adjacent the outlet 106 and are angled in a direction opposite to the direction of travel of the conveyor line. It will be appreciated that in other embodiments, the lance may be located at different positions longitudinally relative to the feed line 102. The spray gun groups are supplied with powder coating material for spraying via a powder feed line (not shown).

In use, a component (not shown) to be coated is conveyed along the conveying line 102 in the direction of arrow 114. The element is suspended below the conveyor line 102 and is translated along a substantially horizontal axis. After the components enter the chamber 101, they are sprayed with coating powder from the gun groups 103a, 103 b. Thus, the rear and lateral portions of the element are coated. The components are sprayed with coating powder from the gun groups 104a, 104b before they leave the chamber 101. Thus, the rear and lateral portions of the element are coated. After leaving the spray booth, at least all vertical surfaces of the element are coated.

In an embodiment, the powder coating and the component are electrostatically charged to attract each other, thereby facilitating the coating process.

The vertical suction inlets 109a and 109b each provide an equal amount of suction. Thus, the element is not pulled to either side of the chamber 102 as it passes through. Since the groups of lances 103a, 103b, 104a, 104b and the vertical suction inlets 109a, 109b are arranged symmetrically with respect to the conveying line 102, the air flow inside the chamber 101 is substantially symmetrical. This provides for applying a substantially uniform powder coating to all surfaces of the element.

Referring to fig. 2, features having the same reference numerals as discussed with reference to fig. 1 are shown from a longitudinal side view. Additionally, the elements 113 to be coated within the chamber 101 are shown, and the spray gun banks 104c, 104d are shown located near the top of the chamber 101. All the groups of spray guns can be moved in the vertical direction in order to spray the powder along the entire vertical height of the element 113. The chamber 101 is particularly suitable for powder coating elongated elements having a considerable length. The chamber 101 may be about 9 meters high and capable of holding the elements to be coated in the range of 6 to 8 meters long. Advantageously, the chamber 101 need only be wide enough to pass the elements between the groups of lances.

In an embodiment, the chamber 101 includes an upper portion 201 and a lower portion 202. References to upper and lower portions (e.g., with respect to vertical suction inlets 109a, 109b) refer to portions that are located laterally of the upper and lower portions of the chamber, respectively.

Referring to fig. 3, features having the same reference numerals as discussed with reference to fig. 1 are shown from a side view. In the illustrated embodiment, the vertical suction manifold 301 branching off to the vertical suction inlet 109b tapers towards the top and bottom of the chamber 101. This ensures that the suction pressure provided remains substantially constant across the height of the chamber 101.

Referring to fig. 4, features having the same reference numerals as discussed with reference to previous figures are shown from an isometric view. Additionally, a powder collection unit 112 is shown attached by piping to the cyclonic pumping systems 110a and 110 b. The powder collection unit 112 collects excess powder, which is sucked into the vertical suction inlets 109a, 109 b.

Referring to fig. 5, a movable baffle 501 is shown at the junction of the vertical suction inlet 109b (or 109a) and the suction source 503. The flap 501 is movable in the direction indicated by arrow 502. The vertical suction inlet 109b is divided into an upper portion and a lower portion by the baffle. When the baffle is in the position shown in fig. 5, the suction source 503 draws air from the upper portion of the vertical suction inlet 109b, thereby diverting the suction force to the corresponding upper portion of the chamber 101. The baffle is movable to a different position (not shown) to configure the suction source 503 to draw air from a lower portion of the vertical suction inlet 109b, thereby diverting the suction force to a corresponding lower portion of the chamber 101. In this way, the available suction from the suction source 503 may be concentrated at different portions of the vertical suction inlet 109 b. This reduces the power required by the suction source (and therefore the size of the associated suction motor, filter, etc.) because there is no need to suction simultaneously over the entire vertical suction inlet 109 b.

In an embodiment, the baffles are located at the vertical midpoint of the vertical suction inlets 109a, 109b so that when turned to either section, an equal level of suction is applied over the length of each section.

In other embodiments (not shown), there may be multiple baffles and/or the degree of movement of the baffle(s) may vary. The suction force levels at different parts of the vertical suction inlet 109b can be configured accurately. For example, the suction force applied to the top of the vertical suction inlet 109b may be high and the suction force applied to the bottom of the vertical suction inlet 109b may be low. The vertical suction inlet 109b may be divided into a plurality of sections, and the selection of the plurality of sections may be configured by the movement of the baffle to the boundary of the sections to apply the suction force. To ensure that a symmetrical air flow about the conveyor line 102 is maintained, any baffles are preferably symmetrically disposed on each opposing vertical suction inlet 109a, 109 b.

Referring to fig. 6, the walls of the chamber 101 each comprise a flexible sheet 601 wound in tension on an upper roller (not shown) and a bottom roller 602. A cleaning device is provided for cleaning a flexible sheet as it is rotated by a roller. In the depicted embodiment, flexible sheet 601 is drawn past a doctor blade 603 that impacts flexible sheet 601. When the powder spray gun is operated, excess coating powder adheres to the flexible sheet facing the interior of the chamber. The rotation of the flexible sheet past the scraper 603 removes at least a portion of this excess coating powder, thereby cleaning the inner surface of the walls of the chamber 101. The vertical suction inlet 109b is provided between two such flexible sheets constituting one side of the chamber 101. Excess coating powder in the chamber 101 is drawn towards the vertical suction inlet and thus also towards the walls of the chamber 101 which are cleaned in the manner discussed above.

It has been found that the cleaning device is most effective when substantially all available suction is concentrated in the lower part of the chamber 101 (i.e. by diverting the suction to the lower part of the vertical suction inlets 109a, 109b when the lance 104 is located laterally of the lower part of the chamber 101). Thus, in use, it is preferred that the flexible sheet 601 only rotate when the spray gun is operating in the lower portion of the chamber 101.

Referring to fig. 7, purge tanks 701a and 701b are provided below the gun groups 104a, 104 b. The tanks 701a and 701b contain means for blowing air at high pressure (e.g. above atmospheric pressure) within the tanks (not shown). The pistons 702a and 702b may be actuated to rotate the guns 104a, 104b so that the nozzles of the gun groups are inserted into the purge bins 701a and 701 b. After the nozzles are inserted into the tanks 701a, 701b, air is blown at the nozzles by a blowing device or blower (not shown), thereby cleaning excess powder paint that has settled on the nozzles, which may contaminate future powder paint, for example, if different colored powders are to be used.

Referring to fig. 8a to 8c, the gun groups 104a, 104b are in a substantially horizontal position (as shown in fig. 8 a) when spraying. As shown in fig. 8b, the gun groups 104a, 104b are rotated to be substantially vertical before cleaning the nozzles. The gun groups 104a, 104b are then inserted into a cleaning tank 701a, 701b as shown in figure 8 c. The nozzles then blow high pressure air through air blowing devices in the cleaning tanks 701a, 701b (not shown). The blowing of air removes excess powder particles that have settled on the nozzles, thereby cleaning them and reducing the risk of contamination of the powder used before after the colour change. After cleaning the nozzles by the blowing device, the spray guns are lifted out of the cleaning tanks 701a, 701b and rotated back to the horizontal position.