JPH0286862A - Rotating sprayer with protecting surround plate - Google Patents

Abstract

PURPOSE: To facilitate the exchange of a manifold having an inlet means at a first surface connected to a coating material supply source by connecting the second surface of the manifold to the inlet of a passage means, providing this second surface with an outlet means and freely attachably and detachably providing the manifold with a housing. CONSTITUTION: A rear cover plate is fixed to the first end of a hollow enclosure plate of housing 21. A fluid rotary atomizer 26 is freely rotatably supported at the inner surface of the cover plate so as to extend from the second end of the enclosure plate. Further, the passage means having the inlet in proximity to the outer flank of the cover plate and the outlet in proximity to the rotary atomizer is disposed through the housing and the coating material is supplied to the rotary atomizer. The first surface of the manifold 22 connected to a coating material supply source is provided with the inlet means and the second surface of the manifold is connected to the inlet of the passage means. The second surface is provided with the outlet means. Further, the housing is freely attachably and detachably mounted to the manifold in such a manner that the cover plate is adjacent to the second surface of the manifold.

Description

[Detailed description of the invention] 11 minutes! TECHNICAL FIELD This invention relates generally to rotary atomizers for coating workpieces, and more particularly to rotary atomizers that provide improved flow rate of coating material through the atomizer and onto a workpiece.

One type of conventional equipment used to apply coatings to raw workpieces is a rotary atomizer. Such an apparatus is particularly useful for painting large amounts of paint over a wide range of surfaces, such as painting automobile bodies. A disk or bell is driven in rotation by an air-powered turbine motor. The paint is from Bell.
It is sent to the inner surface and is ejected as small particles by centrifugal force. A high voltage, typically 30 kv to 125 kv, is applied to the surface of the bell to electrostatically charge the paint particles.

A form of rotary atomizer is disclosed in U.S. Pat. No. 4.555.058.
Disclosed in the issue. This device typically produces 10,0
．． It has a bell that rotates at high speeds ranging from 0.0 rotations to 40,000 rotations. The rotating bell has a plurality of paint openings connected to a paint source. Pressurized air is forced through additional openings in the front plate to direct the spray-forming air to the outside of the bell, thereby forming a stream of paint particles exiting the bell and toward the object to be painted. Point the particle at

U.S. Pat. No. 4,423,840 discloses an ultra-high speed rotating spray bell designed to eliminate air bubbles in the paint used. As the bell rotates at high speed, centrifugal force causes paint to flow through the distribution holes to the generally conical inner flow surface on the injection side of the bell.

Centrifugal force also causes the paint to flow in a continuous film along the inner conical surface to the sharp jet edge between the conical surface and the forward end of the bell. The forward end of the bell has a predetermined wall thickness, the inner surface forms a sharp jet edge, and the outer surface is curved. Even when the rotary atomizing bell is operated at very high speeds, above about 40,000 revolutions per minute, the curvature of the outer spray end eliminates air or other air bubbles trapped in the paint being used. Ru.

The present invention relates to a rotary atomizer having a manifold removably connected to an outer casing or shroud that houses a pneumatic bearing turbine arrangement. The manifold includes inlets for bearing air, braking air, spray forming air, turbine air and paint sources and holes for connection of the magnetic velocity pickup coil. The large diameter end of the outer casing, or shroud, is closed off by a rear cover plate, which includes a section from the facing surface of the manifold for sealingly receiving a corresponding fitting connected to the air inlet. A plurality of protruding holes are formed.

Paint is directed through a centrally located fluid supply tube that passes through a pneumatic turbine motor and is positioned in a paint chamber formed by the forward end of the motor, an atomizer bell, and an annular spray-forming air cap. It extends to the nozzle. The supply tube has a rear flange that fits into a hole in the rear cover plate to precisely align the supply tube with the turbine-driven motor shaft.

A spray forming air cap and an annular spray forming air ring are threaded onto the small diameter end of the shroud. A mating taper formed on the inner surface of the cap and ring defines an annular aperture for spray-forming air that spans the outer edge of the atomizer bell in the inwardly directed flow path. Direct the spray forming air into a thin ring of air.

A flexible cap retainer is attached to the front lid of the pneumatic turbine motor and separates the spray forming air flow path from the exhaust air flow path. In the event that the spray forming air cap becomes dislodged from its threaded mating spray forming air manifold, the cap retainer creates a resilient containment to retain the spray forming air cap.

Exhaust air exits the rear of the turbine and is drawn into the shroud, where it flows forward along the outside of the turbine to provide cooling air and into the paint chamber between the spray forming air cap and the rear of the spray bell. and exit thence through an annular opening formed between the outer edge of the bell and the front edge of the cap. This air prevents paint from being blown back around the outside of the shroud or into the paint chamber. Use of this exhaust air reduces the amount of spray-forming air required and also reduces the required cleaning operations.

Furthermore, as the speed of the air turbine increases, the amount of exhaust air necessarily increases to compensate for the radial momentum of the paint particles.

A pickup coil is positioned adjacent to the travel path of the magnet connected to the looped high voltage wire and is attached to the rear of the turbine wheel of the motor. A wire extends from the atomizer through a toroidal coil to isolate the magnetically generated velocity signal from the effects of high voltages associated with the atomizer.

The above-described advantages of the invention will become apparent to those skilled in the art upon reading the following detailed description of what is presently considered to represent the most preferred embodiment, in light of the accompanying drawings.

X Blood A rotary atomizer 20 according to the present invention includes a housing assembly 22 that is removably secured to a manifold assembly 22 . Housing assembly 21 has a large diameter end for attachment to manifold assembly 22 and includes an outer casing or shroud 23 tapering to an opposite, smaller diameter front end. An annular spray-forming air cap 24 abuts the opening at the small diameter end of shroud 23 . Attached to the cap 24 is an annular atomizing air ring 25 defining an opening in which an atomizing bell 26 is positioned.

The housing device 21 is removably secured to the manifold device 23 by a plurality of latches, which latches include:
It has a first portion 27 attached to the outer surface of the shroud 23 and a second portion 28 attached to the outer surface of the manifold arrangement 22.

As shown, three equally spaced latching mechanisms are used, or any other convenient number and spacing of conventional latching mechanisms may be used as appropriate. The manifold device 22 includes a generally cylindrical manifold body 29.
, and a second latch portion 28 is fixed to the outer curved surface of the main body 29. Similarly, the manifold device body 29
A radially extending stud arrangement 30 is secured to the outer curved surface of the rotary atomizer 20 for attachment to a device for positioning the rotary atomizer 20 on a workstation, such as an industrial robot or reciprocating mechanism (not shown).

The manifold body 29 is formed with a central opening 31 for discharging paint into the housing device 21 as described below. A plurality of fittings also protrude from the surface of the manifold body 29 facing the large end of the shroud 23. These fittings are a spray forming air fitting 32, a discharge air fitting 33, a bearing air fitting 34, a turbine air fitting 35 and a brake air fitting 36. Manifold body 29 is also formed with a speed monitor access port 37 that is used to convey a signal representative of the speed of the pneumatic turbine motor. For example, a magnetic pickup may be attached to the pneumatic turbine motor that generates pulses representing the rotation of the turbine. Signal lines from the pickup extend through access port 37 to the high voltage isolation device and further to appropriate monitoring and display equipment (not shown).

The rotary atomizer 20 of FIG. 1 is shown in partial cross-section in FIG. Housing device 21 and manifold device 2
2 is a first latch portion 27 and a second latch portion 28
are shown connected by. The manifold body 29 has an outer planar surface 38 and an inner planar surface 39 generally parallel to the planar surface 38, with a plurality of holes forming passageways between the two planar surfaces for the various fluids supplied to the housing arrangement 21. is extending. Holes 40 are representative of five passageways for spray forming air, exhaust air, bearing air, turbine air, and brake air, respectively. The end of passage 40 adjacent face 3B is internally threaded to receive a connection to a spray forming air source (not shown). Typically, a conventional source of pressurized air is connected to a conduit having a threaded fitting at the end to thread into the passageway 40. The end of the passage 40 adjacent the inner plane 39 is also internally threaded into which one end of the fitting 32 is screwed.

An O-ring 41 is held in a suitable groove on the protruding end of the pipe fitting 32, and the protruding end extends along the inner circumference of the large diameter end of the pipe fitting 23. It extends inside. Attachment is such that the flat surface 44 of the ring 43 is in contact with the surface 39 of the manifold body 29. The opening of the hole 42 on the surface 44 side is tapered, so that the pipe fitting 32 and the O-ring 4
1 into the hole 42, the wall of the hole 42 is sealed with an O-ring. Thus, the manifold assembly 29, the fitting 32.0 ring 41, and the mounting ring 43 cooperate to
The spray forming air passageway from the source of spray forming air through the manifold arrangement 22 to the housing arrangement 21 is sealed.

Similarly, sealed passages for brake air, exhaust air, turbine air and bearing air are formed in the rear lid of the housing. Removal of latching portions 27 and 28 allows for easy removal of housing assembly 21 from manifold assembly 22 while still attached to a robot or reciprocating mechanism.

Attachment is such that ring 43 engages a flange 45 formed at one end of pneumatic bearing turbine motor 46 . Attachment: ring 43 is attached to motor 46 by at least one screw fastener 47 passing through a radial hole formed in the ring and threaded into a threaded hole formed in flange 45.

The rear cap 4 of the motor 46 within the central area of the ring 43
A plurality of holes (not shown) are formed in 8 in which the projecting ends of fittings 33, 34, 35 and 36 are received. Thus, the end cap 48 and ring 43
It works together as a rear cover plate for 3. turbine motor 4
The other end of 6 passes through an annular spray forming air manifold 49. A spray forming air manifold 49 extends through radial holes formed in the manifold 49 and connects to the motor 46.
The motor 46 is attached to the motor 46 by at least one screw fastener 50 threaded into a threaded hole in the outer surface of the motor 46 .

Holes for radially extending stops 50 are formed in the large diameter portion 51 of the manifold 49. Large diameter portion 51 is connected to a small diameter portion 52 positioned proximate the front end of motor 46 . The reduced diameter portion 52 is formed with external threads that engage internal threads formed on the inner surface of the annular spray forming air cap 24 . Cap 24 is manifold 4
9, and a small diameter front portion 54 connected to both sides of a large diameter central portion 55. The rearwardly facing outer end of the central portion 55 is formed with a cylindrical notch 56 for engaging and retaining the front edge of the shroud 23. The small diameter forward portion 54 is formed with external threads that engage internal threads formed in the inner wall of the annular spray-forming air ring 25 .

Turbine motor 46 includes a front cover plate 57 that cooperates with the motor housing to form a radially extending groove 58 . Groove 58 connects retainer 5 of the annular spray-forming air cap.
Holds the inner end of 9.

The outer end of cap retainer 59 engages the inner surface of spray forming air cap 24 . The front end of the screw drive shaft 60 projects from the lid plate 57 to which the spray bell 26 is attached.

A source of pressurized air (not shown) is connected to the piston chamber of a conventional fluid valve 61, which is connected to a valve fluid system 62. Valve fluid system 62 includes at least one radially extending valve for connection to a paint source (not shown).
It has two screw holes 63. The valve fluid device 62 is
It extends into and is threaded into a central hole 31 formed in the manifold body 29. The valve piston device 61 comprises a stem 61 a that extends through the valve fluid device 62 and as far as a sealing element 61 b that cooperates with a sealing surface formed in the bore 31 . Thus, if the air pressure exceeds a certain value, the valve 61
, valve 61 opens to drain paint from valve fluid system 62, thereby pumping paint through central hole 31 of manifold system 22. The end of central hole 31 adjacent surface 39 receives one end of a rigid fluid supply tube or conduit 64. The fluid line 64 is connected to the outer O
An O-ring 65 is held in the ring groove to seal the inner surface of the central hole 31. A fluid conduit 64 extends through the flange 45, through the center of the fluid motor, and through the drive shaft 60 to the forward end of the drive shaft. A fluid nozzle 66 is mounted inside and projects from the inside of fluid conduit 64. The spray bell 26 has a central hole adjacent to a circular splash plate 67 . As will be described later, the splash prevention plate 67 has a conical central portion facing inward, and this conical central portion is connected to the fluid nozzle 66 which is tapered inward to match the tapered portion of the splash prevention plate 67. Extending into the open end.

For attachment, the hole 42 of the ring 43 is connected to a barbed pipe fitting 68. The barbed end of the pipe fitting 68 connects a certain length of flexible pipe 6.
It is inserted into one end of 9. The barbed end of the second barbed fitting 70 is inserted into the other end of the flexible tube 69. Barbed fitting 70 connects large diameter portion 51 of spray forming air manifold 49
The hole 71 is connected to the hole 71 formed in the hole 71 . Bore 71 extends longitudinally through spray forming air manifold 49 and opens into a cavity 72 defined by spray forming air manifold 49, spray forming air cap 24, spray forming air cap retainer 59, and the housing of turbine motor 46. are doing. A longitudinally extending passageway 73 is formed through the small diameter forward portion 54 and the large diameter central portion 55 of the spray forming air cap 24 .
The outer surface of the small diameter forward portion 54 of 4 and the spray forming air ring 2
A cavity 74 formed between the cavity 74 and the inner surface of the cavity 72 is communicated with each other.

The spray-forming air ring 25 is threaded onto the spray-forming air cap 24 so that the outer surface of the spray-forming air ring 25 forward of the cavity 74 is in abutting engagement with the inner surface of the forward end of the spray-forming air cap 24. , no spray-forming air exits the cavity 74. However, a plurality of grooves or slots 74 (shown in FIG. 4) are present in the forward portion 54.
are formed at equal intervals throughout the outer surface of the front end of the These slots 75 allow the spray-forming air to flow into the cavity 74 between the cap 24 and the ring 25.
and flows into an annular space 75a between the spaced apart front ends of cap 24 and ring 25. The spray-forming air exits from the front edge of the annular space 75 a adjacent the outer edge 76 of the atomizing bell 26 . The slot 75 is
It is formed at an angle to the longitudinal axis of the housing arrangement 21 to create a spray-forming air flow path directed inwardly from around the peripheral edge 76 . Slot 75 and annular space 75a form a thin ring of spray-forming air to compensate for the momentum of atomized paint particles leaking radially from the edge of bell 26. Directing the atomizing air inward provides a smaller pattern and greater efficiency for the atomizing air to control the radiation pattern of the atomizing fluid.

Exhaust air from turbine motor 46 typically exits flat end 48
through holes (not shown) into the fitting 33 and further through the manifold body 29 to an exhaust line (not shown).
is discharged to. However, it is also possible for the exhaust air to exit through at least one hole 45 a of the flange 45 into a cavity 77 formed in the tube of the motor 46 and the shroud 23 . A passageway 78 passes through the large diameter central portion 55 of the spray forming air cap 24 and communicates the cavity 77 with a cavity or chamber 79 formed between the inner surface of the spray forming air cap 24 and the outer surface of the spray bell 26. let As the exhaust air passes through cavity 77, it cools turbine motor 46 and reduces the heat generated by the pneumatic bearings installed therein. Exhaust air exits the cavity 79 between the forward end of the atomizing air cap 24 and the outer edge 76 of the atomizing bell 26 to assist the atomizing air to flow out of the annular space 75a. This spray-forming air prevents paint from blowing back around the outside of the shroud 23 or into the chamber 79. Additionally, because the exhaust air exits forward, less spray-forming air is required to drive the paint toward the target. It also compensates for the increased momentum of the paint particles as the atomizer rotational speed increases. , more spray forming air is required.As the speed of the turbine motor 46 increases, the exhaust air volume increases, so if more spray forming air is needed, the need can be met by the increased exhaust air. .

FIG. 3 shows surface 38 of manifold body 29 and stud arrangement 30 in more detail.

Stud assembly 30 includes a generally cylindrical post 80 extending radially from a semicircular mounting bracket 81 secured to the outer circumferential surface of manifold body 29 by a pair of stops 82 . As mentioned above, the stud device 30 is adapted to be attached to the arm of a robot or reciprocating mechanism.

Also shown in FIG. 3 are a threaded passage 83 for connection to an exhaust line and a threaded passage 8 for connection to a bearing air source.
4. Threaded passageway 85 for connection to turbine air source
and a threaded passageway 86 for connection to a source of brake air. Exhaust air can be directed into cavity 77 by blocking exhaust hole 83 or by providing a rectifier valve.

FIG. 4 shows the cap 24, ring 25, bell 26 and splash plate 67 as well as the cavity or chamber 7 of FIG.
FIG. 9 is a partial cross-sectional view of a part of FIG.

The main body of the splash prevention plate 67 is disc-shaped and has a V-shaped groove 90 formed on its periphery. Groove 90 engages a radially extending flange 90a formed in the opening of spray bell 26. The splash plate 67 is thus snapped into the opening. A conical extension 92 is positioned in the center of the rearwardly facing surface 91 of the splash plate 67 . A pair of diametrically opposed passageways 93 are formed across the conical extension 92 and extend through the forward facing surface 9 of the splash screen 67.
It communicates with a hole 94 formed in 5.

During rotation of the spray bell 26 and splash plate 67, paint exits the fluid nozzle 66 and spreads over the surface of the conical extension 92. Centrifugal force causes paint to flow onto the rear facing surface 96 of the splash plate 67 and then onto the rear facing surface 96 of the spray bell 26. The paint then flows through passage 97,
This passageway 97 is representative of a plurality of equally spaced cylindrically spaced passageways and communicates the surface 96 with the forward facing surface of the outer edge 76 of the spray bell 26. A small portion of paint also passes through passageway 93 and flows into hole 94 . This fluid flows from the holes 94 to the forward facing surface 95 of the splash plate 67.
and flows toward passageway 97 onto the forward facing surface of spray bell 26 . Therefore, the wet paint remains in a thin film on the central portion, and when painting is finished, the central portions of the spray bell 26 and the splash plate 67, as well as the wet inner and outer surfaces of the bell 26, are exposed to the solvent. Helps wash with.

As shown in FIG. 2, at least one generally radially extending hole 98 is formed in the outer surface of the atomizing air ring 25. As shown in FIG. Hole 98 can be engaged with a suitable tool for threading ring 25 onto or removing ring 25 from cap 24. Screw the cap 24 onto the manifold 49 or
A similar hole is provided in the cap 24 for removal from the cap.
It may be formed on the outer surface of.

5 is a schematic diagram of the speed monitoring circuit of the rotary atomizer of FIG. 1; FIG. Motor 46 includes a turbine wheel 101 attached to drive shaft 60 . A pair of permanent magnets 1
02 are mounted at diametrically opposed locations on the turbine wheel.

Although one magnet is sufficient to generate the speed signal, two or more magnets are typically used to maintain balance of the turbine wheel 101.

A pickup coil 103 including a magnetic core 104 is
It is positioned adjacent to the moving path of the magnet 102. Both ends of the pickup coil 103 are connected to both ends of a single loop of a series of loop-shaped dielectrically insulated high voltage wires 105. Pickup coil 103 and magnetic core 104 are positioned inside motor 46 . The high voltage wire 105 is inserted through a hole (not shown) formed in the end cover 48 and further into the manifold body 29.
It extends through a hole 37 formed in the hole 37 .

Typically, the high voltage wire 105 extends at least about 2 feet from the rotary atomizer 20 and passes through the center of the toroidal coil 106.

Both ends of the separation coil 106 are connected to conventional speed monitoring devices 107.
It is connected to the.

Each time one of the magnets 102 passes the pickup coil 103, an electrical pulse is generated in the coil 103 and sent through the high voltage wire 105.

The pulses are inductively connected to toroidal coil 106 and sensed by speed monitoring device 107 .

High voltage wire 105 and toroidal separation coil 10
6 isolates the speed monitoring circuit from a high voltage power source (not shown) connected to the rotary atomizer in a conventional manner for electrostatically charging the paint.

Fluid valve 61 and valve fluid device 62 shown in FIG.
can be used to control the flow of multiple color paints and cleaning solvents to the rotary atomizer 20. Referring to FIG. 6, a schematic diagram of a valve control circuit for supplying paint from a multicolor paint source 111 to a rotary atomizer 20 is shown. Paint source 1
11 is a conventional paint source that typically includes a plurality of paint reservoirs that separately store each color of paint to be sprayed and are connected to the manifold through valve numbers. The outlet from the paint source 111 is connected to the fluid valve 61 and valve fluid system 62 described above.
It communicates with a valve 112 consisting of a combination of. Valve 112 communicates with an inlet of adapter 113 which has an outlet communicating with rotary atomizer 20 . The outlet of the adapter 113 is threaded into a central hole 31 formed in the manifold body 29.

Another valve 114 connects the paint source 111 to the valve 11.
2 and the waste reservoir 115. Valve 114 may be a combination of fluid valve 61 and valve fluid device 62. A similar valve 116 is connected between adapter 113 and solvent source 117.

When the rotary sprayer 20 is used to paint an object, such as an automobile, paint of a selected color is applied to the paint source 1 via a valve 112 that is pneumatically actuated to the open position.
11 and is pressed out. For paint, use adapter 1
13 to a rotary atomizer 20. Typically, the next car body to be painted receives a different color of paint. Paint source 111 cuts off the supply of paint for the color being used and injects a coupled solvent through conduit toward valve 112. However, valve 112 is closed and waste valve 114 is opened to waste reservoir 115. Thus, the paint residue of the sprayed color flows to the waste reservoir and the coupled solvent cleans the lines. The coupled solvent is followed by a new color of paint to be sprayed, and the waste valve 114 is not closed and the first The operation timing is such that the valve 112 is not opened.

As soon as a different color paint is applied, valve 116 is opened and solvent is ejected and forced from solvent reservoir 117 through adapter 113 and rotary atomizer 20 for a short period of time at high pressure to clean the paint flow path and spray bell. . Valve 112 is then reopened for a new color of paint after valve 11B is closed.

In accordance with the provisions of the patent laws, the invention has been described in terms of what are considered to be its preferred embodiments. However, it should be noted that the invention may be practiced otherwise than as specifically illustrated and described without departing from the spirit or scope of the invention.

[Brief explanation of the drawing]

1 is an exploded perspective view of a rotary atomizer according to the present invention; FIG. 2 is a partial cross-sectional side view of the rotary atomizer shown in FIG. 1; and FIG. 3 is a side view of the rotary atomizer shown in FIG. 4 is an enlarged partial cross-sectional side view of the forward end of the rotary atomizer of FIG. 1; FIG. 5 is a schematic diagram of the velocity sensing circuit of the rotary atomizer of FIG. 1; FIG. 6 is a schematic diagram of a valve system for the rotary atomizer of FIG. 1. 21φ... Housing, 26... Spray bell, 64... Supply pipe, 67... Splash prevention plate. FIG, 1 FIG, 2

Claims (7)

[Claims] (1) a housing comprising a hollow shroud having a first end, a second end and a rear cover plate secured to the first end; and a housing extending from the second end of the shroud. a fluid rotary atomizer rotatably supported on an inner surface of the cover plate; an inlet proximate to the outer surface of the cover plate; and an outlet proximate to the rotary atomizer; passage means extending from and for supplying paint to said rotary atomizer, and having an inlet means on a first surface adapted to be connected to a paint supply source and connected to an inlet of said passage means; a manifold having an outlet means on a second side thereof; and fastening means for removably attaching the housing to the manifold such that the cover plate is adjacent the second side of the manifold. A rotary sprayer for painting articles with a fluid, characterized by: (2) the manifold has at least one air passageway, a first manifold face having an end adapted to be connected to a source of pressurized air and a second manifold face extending from the end; an end for holding a mounting member formed through the air passageway, and an outer surface of the cover plate having an aperture for receiving the mounting member when the housing is attached to a manifold. The rotary atomizer according to claim (1). (3) the manifold has a plurality of passageways, each passageway having a mounting member extending from a second manifold surface; Rotary atomizer according to claim 2, characterized in that it has a further hole for receiving a mounting member. (4) Paint passage means extending through the housing includes a paint supply pipe fixed to the cover plate so as to extend coaxially with the rotary atomizer, the pipe protruding from an outer surface of the cover plate. A rotary atomizer according to claim 1, wherein the housing has a free end for sliding into the paint outlet means of the manifold when the housing is attached to the manifold. 5. The housing of claim 4, further comprising means for forming a liquid-tight seal between the free end of the tube and the manifold when the housing is attached to the manifold. Rotary atomizer as described. (6) An air-driven turbine is fixed to the cover plate, and for rotatably supporting the rotary atomizer on the cover plate, the turbine has a hollow drive shaft having a free end fixed to the rotary atomizer. 5. A rotary atomizer according to claim 4, further comprising: a paint supply tube extending through the hollow drive shaft. (7) An air-driven turbine is fixed to the cover plate, and for rotatably supporting the rotary atomizing device on the cover plate, the turbine has a hollow drive shaft having a free end fixed to the rotary atomizing device. 2. A rotary atomizer as claimed in claim 1, further comprising: said passage means extending through said hollow drive shaft.