WO2008020812A1 - System for improved powder coating of duct fittings and process for same - Google Patents

System for improved powder coating of duct fittings and process for same Download PDF

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Publication number
WO2008020812A1
WO2008020812A1 PCT/SG2007/000249 SG2007000249W WO2008020812A1 WO 2008020812 A1 WO2008020812 A1 WO 2008020812A1 SG 2007000249 W SG2007000249 W SG 2007000249W WO 2008020812 A1 WO2008020812 A1 WO 2008020812A1
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WO
WIPO (PCT)
Prior art keywords
powder coating
duct
oven
duct fitting
fitting
Prior art date
Application number
PCT/SG2007/000249
Other languages
French (fr)
Inventor
Yong Keng Tan
Lih Meng Yong
Shan Xin Cai
Yong Song Zheng
Ya Qun Huang
Original Assignee
Kenyon Engineering Pte Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kenyon Engineering Pte Ltd filed Critical Kenyon Engineering Pte Ltd
Publication of WO2008020812A1 publication Critical patent/WO2008020812A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D7/00—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials
    • B05D7/14—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies
    • B05D7/146—Processes, other than flocking, specially adapted for applying liquids or other fluent materials to particular surfaces or for applying particular liquids or other fluent materials to metal, e.g. car bodies to metallic pipes or tubes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B13/00—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00
    • B05B13/06—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00 specially designed for treating the inside of hollow bodies
    • B05B13/0645—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00 specially designed for treating the inside of hollow bodies the hollow bodies being rotated during treatment operation
    • B05B13/0654—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00 specially designed for treating the inside of hollow bodies the hollow bodies being rotated during treatment operation and a treating nozzles being translated through the hollow bodies in a direction essentially parallel to the rotational axis
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B7/00—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas
    • B05B7/14—Spraying apparatus for discharge of liquids or other fluent materials from two or more sources, e.g. of liquid and air, of powder and gas designed for spraying particulate materials
    • B05B7/1481—Spray pistols or apparatus for discharging particulate material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/002—Processes for applying liquids or other fluent materials the substrate being rotated
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D1/00—Processes for applying liquids or other fluent materials
    • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
    • B05D1/12—Applying particulate materials
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D2401/00—Form of the coating product, e.g. solution, water dispersion, powders or the like
    • B05D2401/30—Form of the coating product, e.g. solution, water dispersion, powders or the like the coating being applied in other forms than involving eliminable solvent, diluent or dispersant
    • B05D2401/32—Form of the coating product, e.g. solution, water dispersion, powders or the like the coating being applied in other forms than involving eliminable solvent, diluent or dispersant applied as powders

Definitions

  • the present invention relates to a system for an improved powder coating of duct fittings and a process for powder coating of duct fittings using the said system.
  • Stepl Duct fittings are placed inside an oven for pre-heating to the desired temperature suitable for the application of powder coating.
  • Step 2 After the pre-heating phase has ended, the duct fittings are removed from the oven for the application of powder coating via conventional electrostatic spraying method.
  • Step 3 The duct fittings are then returned to the oven to allow baking and curing of the powder coating.
  • Steps 2 and 3 above are repeated for each subsequent layer of powder coating applied and the duct fittings need to be removed repeatedly from the oven for the powder coating process resulting in long processing times and low production output efficiency.
  • the duct fitting is held stationary and the spray head has to be rotated along the longitudinal axis of the duct to ensure the powder is evenly sprayed onto the internal walls of the duct.
  • the application of a rotary spray with forward and backward movement fulfilling the above requirement would no doubt be uneven and inefficient.
  • the inventors have studied the problems and propose placing the duct fitting in a purpose-made oven to heat the duct fitting and which is continuously rotated so as to facilitate the application of powder coating onto the internal walls of the duct fitting and then for curing of powder coating. It is therefore desirable to have a system which can apply one or more layers of powder coating onto the internal walls of a duct fitting to obtain a more uniform and improved coating finish and effective thickness without repeated movements in and out of an oven. It is also desirable for such a system to reduce loss of heat energy and powder coating and reduce production time for powder coating a duct fitting.
  • a first object of the invention is a system for improved powder coating of the internal walls of a duct fitting, the duct fitting having a first and second end, the system comprising:- an oven, the oven comprising a base and a removable top insulated cover with an oven cavity formed therein; duct attachment means; a drive mechanism; heating means; and an automatic powder coating sprayer; wherein the first end and second end of the duct fitting is attached to each end of the oven by the attachment means and placed within the oven cavity, the automatic powder coating sprayer applying a first powder coating to the internal walls of the said duct fitting, which is continuously rotated by the drive mechanism, so that a first powder coating is applied evenly throughout the internal walls of the said duct fitting, while being heated continuously by the heating means, so that the first powder coating is baked and cured, followed by application and heating of additional layers of powder coating to the internal walls of the duct fitting, so that the each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder
  • the system has an oven comprising of base and a top insulated cover forming an oven cavity wherein the top insulated cover is removable to allow the duct fitting to be placed onto the base of the oven, said duct fitting secured within the oven cavity by the duct attachment means.
  • the system has a drive mechanism consisting of an electric motor, clamp down wheel and at least two traction wheels, for rotation of the duct fitting, the first and second end of which are attached to the duct attachment means.
  • the system has duct attachment means which consisting of a collar for each end of the duct fitting, to secure the duct fitting within the cavity where the temperature is more even and also act to cut off powder coating from reaching the top insulated cover and base of the oven and the external surface of the duct.
  • duct attachment means consisting of a collar for each end of the duct fitting, to secure the duct fitting within the cavity where the temperature is more even and also act to cut off powder coating from reaching the top insulated cover and base of the oven and the external surface of the duct.
  • the system has duct attachment means which consist of a grip for each end of the duct fitting, to secure the duct fitting onto the oven.
  • the system has heating means consisting of a plurality of electrical elements in the oven.
  • the system has heating means consisting of a plurality of gas burners in the oven.
  • the system has a PLC controller to control the drive mechanism, to start and control movement of the automatic powder coating sprayer and to regulate the baking and curing temperature throughout the application, baking and curing of powder coatings on the internal walls of the duct fittings.
  • a PLC controller to control the drive mechanism, to start and control movement of the automatic powder coating sprayer and to regulate the baking and curing temperature throughout the application, baking and curing of powder coatings on the internal walls of the duct fittings.
  • the baking temperature of the oven is from 250 0 C to 350 0 C.
  • the curing temperature range of the oven is from 270 0 C to 300 0 C.
  • the controller has a plurality of temperature sensors which turns on or turns off the electric heaters to regulate the baking and curing temperature range and by releasing or keeping heat within the oven and also to improve the circulation of heat within the oven.
  • the system has a plurality of hot flue gas inlets and outlets wherein at slow starting temperature, the temperature sensors will sense the oven temperature is below the baking and curing temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to raise the temperature in the oven and if the oven temperature is over the baking and curing temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to lower the temperature in the oven.
  • the system further comprises a high temperature fan and hot air/gas suction duct for re-circulation of hot air from within the oven and back into the ends of the oven so that all parts of the oven can be maintained at an even baking and curing temperature range.
  • the system has an automatic powder coating sprayer having a spray head, said sprayer mounted on a set of guide rails, laid parallel to the horizontal axis of the duct fitting, the spray head movable by the electric motor of the drive mechanism, along the length of the internal walls of the duct fitting to spray powder coating onto the entire internal walls of the duct fitting.
  • the system has an automatic powder coating sprayer which will be activated by the controller and move into the internal of the duct to perform spraying of powder coating when the temperature of the oven is within the baking temperature range.
  • the system further comprising an oven frame and a pulley system to open the oven for monitoring of the duct fitting and for mounting the duct attachment means.
  • the oven frame has an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel.
  • the pulley system is fitted to the oven frame and consists of fixed pulleys, with steel cables attached at one end to the clamp down wheels and at the other end attached to a counter weight block.
  • the rotation speed of the duct fittings is from 6 rpm to 1440 rpm.
  • a second object of the invention is for an improved powder coating process for the internal walls of a duct fitting, using the system for improved powder coating of the internal walls of a duct fitting, comprising these steps :- attaching a first and second end of the duct fitting to duct attachment means; loading and enclosing the duct fitting complete with the end attachments in an oven cavity of an oven; using the heating means to heat the duct fitting until the temperature reaches baking temperature range; whereupon the automatic powder coating sprayer will move into the oven and along the horizontal axis of the internal wall of the duct fitting; said drive mechanism rotating the duct fitting so that the sprayer will spray a first layer of powder coating evenly onto all areas of the internal wall of the duct fitting; said powder coating being heated continuously by the heating means so that the first layer of powder coating is baked and cured, followed by application and heating of additional layers of powder coating to the internal walls of the duct fitting, so that each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder coating resulting in
  • the process further comprise a step of clamping the duct attachment means to the duct fitting, said duct attachment means held by an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel so that when the duct fitting is rotated, said clamp down wheel will position the rotation of the duct attachment means so that the duct fitting is rotated along the same axis.
  • the process comprise the additional steps of controlling the heat inside the oven cavity to ensure a consistent and stable operating environment for the powder coating process, while the powder coating is baked and cured to form a first layer on the internal walls of the duct fitting, followed by additional layers of powder coating, by turning on or turning off the electrical power supply to one or more of the electrical heater elements or by regulating the hot flue gas supply and exhaust, depending on the size of the oven, opening the inlet flue gas damper and closing the flue gas outlet damper when the temperature is below the baking and curing range, closing the inlet flue gas damper and opening the flue gas outlet damper when the temperature is over the baking and curing range, and re-circulating the hot air or flue gas during the entire heating, baking and curing process.
  • Fig. 1 is a side view showing the construction of essential parts of an example of a system for powder coating a duct fitting according to an embodiment of the present invention.
  • Fig. 2 is a front view of the same system.
  • Fig. 1 is a side view showing the construction of essential parts of an example of a system for powder coating of a duct fitting.
  • Fig. 2 is a front view of the same system.
  • the system has an oven frame (4) to which an oven (5) is attached.
  • the oven (5) comprises a removable top insulated cover (7) and a base piece (13) which forms an oven cavity (14) where the duct fitting (8) is loaded.
  • the duct fitting is not limited to a straight configuration.
  • This system also includes a drive mechanism that rotates the duct fitting (8) inside the oven cavity (14) along its longitudinal axis and an automatic sprayer (20) that performs the spraying of powder coating onto the internal walls of the duct fitting (8) which is placed inside the oven cavity (14).
  • the drive mechanism also have the capability to rotate duct fitting of curved and angled configurations.
  • the automatic sprayer (20) includes the spray head (15) which travels into and out of the oven cavity (14).
  • the drive mechanism includes the duct attachment piece (9) that is fastened to the duct fitting (8) to facilitate rotation.
  • One end of this duct attachment piece (9) extends from the side of the oven (5) into the oven cavity (14).
  • the first and second duct attachment pieces (9) extend from the opposite sides of the oven (5) into the oven cavity (14).
  • the spray head (15) of the automatic sprayer (20) moves pass the end of the first duct attachment (9) into the interior of the duct fitting (8) within the oven cavity (14).
  • Mounted onto the oven frame (4) are traction wheels (11) and clamp-down wheels (6) whose axes are aligned in parallel to the longitudinal axis of the duct attachment pieces (9).
  • the external circumferential surfaces of the traction wheels (11) and clamp-down wheels (6) are in contact with the external circumferential surfaces of the duct attachment pieces (9).
  • the traction wheels (11) are coupled to the drive mechanism.
  • the drive mechanism's electric motor (19) is mounted onto the oven frame (4) and this electric motor's (19) output gear shaft is wound with a chain-link (17).
  • the electric motor (19) is coupled to the traction wheel (11) through the chain-link (17).
  • the fixing wheel for chain-link (16) mounted on the oven frame (4) serves to tighten the chain-link (17) such that the electric motor (19) can drive the traction wheels (11) via the chain-link (17) which in turn allows the traction wheels (11) to rotate the duct attachment pieces (9) through frictional forces.
  • electric heating elements (12) are fitted inside the oven cavity (14) to facilitate heating and these electric heating elements (12) are connected to the control panel (18).
  • the control panel (18) which is mounted on the oven frame (4), controls the switching on and off of electric heating elements (12) and also dynamically adjusts the power output of electric heating element (12) to achieve the desired oven temperature.
  • hot flue gas from LPG/LNG burner is used for heating instead of electric heating elements.
  • the control of oven temperature is also by control panel.
  • the control will close the inlet flue gas damper (29) on the inlet flue gas duct (24) and open the outlet flue gas damper (30) on the exhaust flue gas duct (25) when the oven temperature is too high.
  • the control panel When the oven temperature is too low, the control panel will open the inlet flue gas damper (29) and close the outlet flue gas damper (30).
  • the oven cavity (14) temperature is made more even by circulating the hot air or flue gas through a hot air/gas suction duct (26) through a high temperature fan (23) and blow back the hot air/gas back into the oven through the hot air/gas return duct (27).
  • the temperature inside the oven cavity (14) can be controlled within 500°C but based on actual implementation, the characteristics of the powder coating material has limited the oven cavity (14) temperature to 350°C.
  • the oven (5) includes the base piece (13) of the oven and the top insulated cover (7) of the oven.
  • Step 1 Load the duct fitting into the oven, mounting the duct fitting onto the oven with the first end and second end of the duct fitting attached to the first and second duct attachment pieces.
  • the duct attachment pieces rests on the traction wheels.
  • the rotational speed is then set.
  • the duct fitting is therefore rotating inside the oven, with the turning of the traction wheels, which is driven by the electric motor (19).
  • the clamp-down wheels will hold the duct attachment piece in place.
  • the duct fitting is then heated up as it rotates along its longitudinal axis.
  • Step 2 While allowing the continuously heated duct fitting to remain rotating inside the oven, the automatic sprayer is moved along or parallel to the longitudinal axis of the interior of the duct fitting. The automatic sprayer applies the powder coating by spraying onto the internal wall of the duct fitting.
  • Step 3 After the completion of the spraying process, the duct fitting is allowed to remain inside the oven for the dwell time to elapse so that the powder coating could bake and cure.
  • Step 2 is repeated after the completion of Step 3 and this process is iterated depending on the number of coats to be applied.
  • the duct fitting is removed from the oven for cooling down.
  • the rotational speed of the duct fitting is adjustable within the range from 6 - 1440 rpm to ensure that powder is evenly sprayed onto the internal wall of the duct fittings.
  • the temperature control is achieved by a PLC controller switching on/off the electrical heater elements or by PLC controller to regulate the hot flue gas supply and exhaust.
  • the top insulated cover of the oven (7) needs to be lifted up to allow the duct fitting (8) to be loaded onto the oven (5), after which the top insulated cover of the oven (7) is lowered down and closed. Both ends of the duct fitting (8) are fastened with the duct attachment piece (9).
  • the electric heating element (12) can then be switched on to heat up the oven cavity (14).
  • the electric heating elements (12) are installed inside the base piece of the oven (13) and these electric heating elements (12) are located close to the duct fitting (8).
  • the duct fitting (8) When the electric heating elements (12) heats up the oven cavity (14), the duct fitting (8) is rotated by the duct attachment pieces (9) and as a result the duct fitting (8) is evenly heated up.
  • the spray head (15) of the automatic sprayer (20) When the temperature within the oven cavity (14) reaches the desired set-point value, the spray head (15) of the automatic sprayer (20) is activated to move into the duct fitting (8). The spray head (15) then begins to perform spraying of the powder coating onto the internal walls of the duct fitting (8). hi the process of the spraying, the duct fitting (8) remains rotated by the duct attachment pieces (9) and results in the powder being evenly coated onto the internal walls of the duct fitting (8).
  • the automatic sprayer (20) While the spray head (15) is performing the spraying process, the automatic sprayer (20) needs to move along or parallel to the longitudinal axis of the duct fitting (8). To facilitate this, a set of guide rails for the automatic sprayer (21) are installed aligned in parallel to the longitudinal axis of the duct attachment piece (9). The automatic sprayer (20) is mounted onto these guide rails (21) and as the automatic sprayer (20) moves along the guide rails (21) driven by the mechanised screw (22), the spray head (15) moves along or parallel to the duct fitting's (8) longitudinal axis into the interior of the duct fitting (8).
  • the clamp-down wheels (6) are fitted to press down on the external circumferential surfaces of the duct attachment pieces (9).
  • fixing brackets for the clamp-down wheels (10) are fitted on the oven frame (4) to both sides of the duct attachment pieces (9) and the clamp-down wheels (6) are fitted to these fixing brackets (10).
  • the system for a duct fitting with improved powder coating includes the supporting frame of the oven and the main body of the oven.
  • the main body of the oven is an enclosure that could accommodate the duct fitting and it includes all parts of the rotational drive mechanism that rotates the duct fitting on its longitudinal axis and the automatic sprayer that performs the spraying of powder coating onto the duct fitting's internal walls.
  • the automatic sprayer mentioned herein consists of a spray gun head that moves into and out of the oven along its longitudinal axis while the rotational drive mechanism includes the customized duct attachment pieces that are fastened to the duct fitting such that one end of each duct attachment piece is extended into the oven.
  • Fitted to the oven frame are traction wheels and clamp-down wheels whose axes are oriented in parallel to that of the duct attachment pieces.
  • the external circumferential surfaces of the traction wheels and the clamp-down wheels are in contact with the external circumferential surfaces of the duct attachment pieces.
  • the traction wheel is coupled to the power drive mechanism which consisted of an electric motor mounted on the oven frame that is coupled to the traction wheel by a chain-link that is wound onto its output gear shaft.
  • each duct attachment piece there is an adjustable fixing bracket on the oven frame from which the clamp-down wheel is attached.
  • a pulley system that consisted of steel cables with one end attached to the clamp-down wheel fixing bracket and the other end attached to a counterweight block.
  • Mounted on the oven frame is a pair of traction wheels whose axes are aligned on the same horizontal plane. These traction wheels are located below the duct attachment pieces and in contact with the latter's external circumferential surfaces, supporting them above.
  • Each end of the attachment piece is covered by an insulated cap.
  • On the cap nearer to the spray gun is an opening for the sprayer to access into the inner part of the duct.
  • the duct fitting will rotate together with the attachment pieces during operation. While the automatic sprayer performs the spraying of powder coating onto the internal walls of the duct fitting, the fact that the duct fitting still remains inside the continuously heated oven enclosure will ensure that a consistent and stable operating environment so that the powder coating process is maintained. This also meant that spraying and curing can be completed in a single step without the hassle of bringing the duct fitting into and out of the oven repeatedly, cutting down on processing time and improving the production output efficiency.
  • Heating of the oven can be done by means of electric heaters installed within the chamber of the oven, i.e., the space formed by the outside of the duct fitting, the attachment pieces and the oven body.
  • electric heaters installed within the chamber of the oven, i.e., the space formed by the outside of the duct fitting, the attachment pieces and the oven body.
  • a bigger oven is required and consequently the heat needed for baking and curing is by introducing hot flue gas from burning of LPG or LNG.
  • the internal wall of the duct fitting is evenly powder coated thus improving the quality of the coated product.
  • the rotation of the duct fitting also enables the temperature to be more even.
  • a recirculation system will suck hot air/hot gas from the chamber of the oven and blow back to the 2 ends of the oven.
  • rotating a duct fitting is simpler to attain instead of a rotational mechanism to be fitted onto the spray gun head.
  • the inventor has greatly simplified the design and installation of this customized powder coating equipment.
  • the internal wall of the duct fitting is evenly powder coated thus improving the quality of the coated product.

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  • Life Sciences & Earth Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Wood Science & Technology (AREA)
  • Spray Control Apparatus (AREA)
  • Application Of Or Painting With Fluid Materials (AREA)
  • Electrostatic Spraying Apparatus (AREA)
  • Coating Apparatus (AREA)

Abstract

A system for improved powder coating of the internal walls of a duct fitting, comprising an oven; duct attachment means; a drive mechanism; heating means; and an automatic powder coating sprayer. The duct fitting is enclosed within the oven while an automatic powder coating sprayer applies layers of powder coating, sequentially, onto the internal walls of the said duct fitting. The duct fitting is continuously rotated by the drive mechanism, while being heated continuously by the heating means, so that the each layer of powder coating is baked and cured, resulting in an improved powder coating for the duct fitting.

Description

SYSTEM FOR IMPROVED POWDER COATING OF DUCT FITTINGS AND PROCESS FOR SAME
FIELD OF THE INVENTION The present invention relates to a system for an improved powder coating of duct fittings and a process for powder coating of duct fittings using the said system.
PRIOR ART
The existing technique for the application of powder coating to the internal walls of a duct fitting involves the following steps:
Stepl: Duct fittings are placed inside an oven for pre-heating to the desired temperature suitable for the application of powder coating.
Step 2: After the pre-heating phase has ended, the duct fittings are removed from the oven for the application of powder coating via conventional electrostatic spraying method.
Step 3: The duct fittings are then returned to the oven to allow baking and curing of the powder coating.
Steps 2 and 3 above are repeated for each subsequent layer of powder coating applied and the duct fittings need to be removed repeatedly from the oven for the powder coating process resulting in long processing times and low production output efficiency. PROBLEMS TO BE SOLVED BY THE INVENTION
Practitioners of the existing technique described above face the following problems:
1) Uneven powder coating as subsequent coatings are harder to apply due to electrostaticity of powder coat. 2) Inefficient use of powder coating, as the spraying is carried out in an open confined area.
3) Heat loss due to opening and closing of oven, resulting in higher energy costs and more energy consumption in order to raise the oven's temperature every time the duct fitting is placed back into the oven. 4) Long processing time due to movement in and out of the oven, application of powder coating and baking and curing taking place in sequenced steps.
In the existing technique, the duct fitting is held stationary and the spray head has to be rotated along the longitudinal axis of the duct to ensure the powder is evenly sprayed onto the internal walls of the duct. The application of a rotary spray with forward and backward movement fulfilling the above requirement would no doubt be uneven and inefficient.
The inventors have studied the problems and propose placing the duct fitting in a purpose-made oven to heat the duct fitting and which is continuously rotated so as to facilitate the application of powder coating onto the internal walls of the duct fitting and then for curing of powder coating. It is therefore desirable to have a system which can apply one or more layers of powder coating onto the internal walls of a duct fitting to obtain a more uniform and improved coating finish and effective thickness without repeated movements in and out of an oven. It is also desirable for such a system to reduce loss of heat energy and powder coating and reduce production time for powder coating a duct fitting. These and other subsidiary objects of the invention would be apparent from a reading of the description of the embodiments of the invention.
MEANS FOR SOLVING THE PROBLEM A first object of the invention is a system for improved powder coating of the internal walls of a duct fitting, the duct fitting having a first and second end, the system comprising:- an oven, the oven comprising a base and a removable top insulated cover with an oven cavity formed therein; duct attachment means; a drive mechanism; heating means; and an automatic powder coating sprayer; wherein the first end and second end of the duct fitting is attached to each end of the oven by the attachment means and placed within the oven cavity, the automatic powder coating sprayer applying a first powder coating to the internal walls of the said duct fitting, which is continuously rotated by the drive mechanism, so that a first powder coating is applied evenly throughout the internal walls of the said duct fitting, while being heated continuously by the heating means, so that the first powder coating is baked and cured, followed by application and heating of additional layers of powder coating to the internal walls of the duct fitting, so that the each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder coating resulting in an improved powder coating for the duct fitting.
Preferably the system has an oven comprising of base and a top insulated cover forming an oven cavity wherein the top insulated cover is removable to allow the duct fitting to be placed onto the base of the oven, said duct fitting secured within the oven cavity by the duct attachment means.
Preferably, the system has a drive mechanism consisting of an electric motor, clamp down wheel and at least two traction wheels, for rotation of the duct fitting, the first and second end of which are attached to the duct attachment means.
Preferably the system has duct attachment means which consisting of a collar for each end of the duct fitting, to secure the duct fitting within the cavity where the temperature is more even and also act to cut off powder coating from reaching the top insulated cover and base of the oven and the external surface of the duct.
Alternatively, the system has duct attachment means which consist of a grip for each end of the duct fitting, to secure the duct fitting onto the oven.
Preferably, the system has heating means consisting of a plurality of electrical elements in the oven.
Alternatively, the system has heating means consisting of a plurality of gas burners in the oven.
Preferably the system has a PLC controller to control the drive mechanism, to start and control movement of the automatic powder coating sprayer and to regulate the baking and curing temperature throughout the application, baking and curing of powder coatings on the internal walls of the duct fittings.
Preferably the baking temperature of the oven is from 2500C to 350 0C. Preferably the curing temperature range of the oven is from 2700C to 3000C.
Preferably, the controller has a plurality of temperature sensors which turns on or turns off the electric heaters to regulate the baking and curing temperature range and by releasing or keeping heat within the oven and also to improve the circulation of heat within the oven.
Preferably, the system has a plurality of hot flue gas inlets and outlets wherein at slow starting temperature, the temperature sensors will sense the oven temperature is below the baking and curing temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to raise the temperature in the oven and if the oven temperature is over the baking and curing temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to lower the temperature in the oven.
Preferably the system further comprises a high temperature fan and hot air/gas suction duct for re-circulation of hot air from within the oven and back into the ends of the oven so that all parts of the oven can be maintained at an even baking and curing temperature range.
Preferably, the system has an automatic powder coating sprayer having a spray head, said sprayer mounted on a set of guide rails, laid parallel to the horizontal axis of the duct fitting, the spray head movable by the electric motor of the drive mechanism, along the length of the internal walls of the duct fitting to spray powder coating onto the entire internal walls of the duct fitting.
Preferably, the system has an automatic powder coating sprayer which will be activated by the controller and move into the internal of the duct to perform spraying of powder coating when the temperature of the oven is within the baking temperature range.
Preferably the system further comprising an oven frame and a pulley system to open the oven for monitoring of the duct fitting and for mounting the duct attachment means.
Preferably the oven frame has an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel. Preferably the pulley system is fitted to the oven frame and consists of fixed pulleys, with steel cables attached at one end to the clamp down wheels and at the other end attached to a counter weight block.
Preferably the rotation speed of the duct fittings is from 6 rpm to 1440 rpm.
A second object of the invention is for an improved powder coating process for the internal walls of a duct fitting, using the system for improved powder coating of the internal walls of a duct fitting, comprising these steps :- attaching a first and second end of the duct fitting to duct attachment means; loading and enclosing the duct fitting complete with the end attachments in an oven cavity of an oven; using the heating means to heat the duct fitting until the temperature reaches baking temperature range; whereupon the automatic powder coating sprayer will move into the oven and along the horizontal axis of the internal wall of the duct fitting; said drive mechanism rotating the duct fitting so that the sprayer will spray a first layer of powder coating evenly onto all areas of the internal wall of the duct fitting; said powder coating being heated continuously by the heating means so that the first layer of powder coating is baked and cured, followed by application and heating of additional layers of powder coating to the internal walls of the duct fitting, so that each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder coating resulting in an improved powder coating for the duct fitting.
Preferably the process further comprise a step of clamping the duct attachment means to the duct fitting, said duct attachment means held by an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel so that when the duct fitting is rotated, said clamp down wheel will position the rotation of the duct attachment means so that the duct fitting is rotated along the same axis.
Preferably the process comprise the additional steps of controlling the heat inside the oven cavity to ensure a consistent and stable operating environment for the powder coating process, while the powder coating is baked and cured to form a first layer on the internal walls of the duct fitting, followed by additional layers of powder coating, by turning on or turning off the electrical power supply to one or more of the electrical heater elements or by regulating the hot flue gas supply and exhaust, depending on the size of the oven, opening the inlet flue gas damper and closing the flue gas outlet damper when the temperature is below the baking and curing range, closing the inlet flue gas damper and opening the flue gas outlet damper when the temperature is over the baking and curing range, and re-circulating the hot air or flue gas during the entire heating, baking and curing process.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side view showing the construction of essential parts of an example of a system for powder coating a duct fitting according to an embodiment of the present invention.
Fig. 2 is a front view of the same system.
EMBODIMENTS OF THE INVENTION
The present invention will now be described in detail with reference to the accompanying drawings showing the preferred embodiment. Fig. 1 is a side view showing the construction of essential parts of an example of a system for powder coating of a duct fitting. Fig. 2 is a front view of the same system. The system has an oven frame (4) to which an oven (5) is attached. The oven (5) comprises a removable top insulated cover (7) and a base piece (13) which forms an oven cavity (14) where the duct fitting (8) is loaded. The duct fitting is not limited to a straight configuration. This system also includes a drive mechanism that rotates the duct fitting (8) inside the oven cavity (14) along its longitudinal axis and an automatic sprayer (20) that performs the spraying of powder coating onto the internal walls of the duct fitting (8) which is placed inside the oven cavity (14). The drive mechanism also have the capability to rotate duct fitting of curved and angled configurations. The automatic sprayer (20) includes the spray head (15) which travels into and out of the oven cavity (14).
The drive mechanism includes the duct attachment piece (9) that is fastened to the duct fitting (8) to facilitate rotation. One end of this duct attachment piece (9) extends from the side of the oven (5) into the oven cavity (14). As shown in Fig. 1, there are two duct attachment pieces (9). The first and second duct attachment pieces (9) extend from the opposite sides of the oven (5) into the oven cavity (14). The spray head (15) of the automatic sprayer (20) moves pass the end of the first duct attachment (9) into the interior of the duct fitting (8) within the oven cavity (14). Mounted onto the oven frame (4) are traction wheels (11) and clamp-down wheels (6) whose axes are aligned in parallel to the longitudinal axis of the duct attachment pieces (9). The external circumferential surfaces of the traction wheels (11) and clamp-down wheels (6) are in contact with the external circumferential surfaces of the duct attachment pieces (9). There is a total of one pair of traction wheels (11) whose axes are aligned on the same horizontal plane. These traction wheels (11) are located at the bottom of the duct attachment pieces (9) and in contact with the external circumferential surfaces of the duct attachment pieces (9), supporting them above. The traction wheels (11) are coupled to the drive mechanism. The drive mechanism's electric motor (19) is mounted onto the oven frame (4) and this electric motor's (19) output gear shaft is wound with a chain-link (17). The electric motor (19) is coupled to the traction wheel (11) through the chain-link (17). The fixing wheel for chain-link (16) mounted on the oven frame (4) serves to tighten the chain-link (17) such that the electric motor (19) can drive the traction wheels (11) via the chain-link (17) which in turn allows the traction wheels (11) to rotate the duct attachment pieces (9) through frictional forces.
Inside the oven (5), electric heating elements (12) are fitted inside the oven cavity (14) to facilitate heating and these electric heating elements (12) are connected to the control panel (18). The control panel (18), which is mounted on the oven frame (4), controls the switching on and off of electric heating elements (12) and also dynamically adjusts the power output of electric heating element (12) to achieve the desired oven temperature. For bigger ovens, hot flue gas from LPG/LNG burner is used for heating instead of electric heating elements. In this case, the control of oven temperature is also by control panel. The control will close the inlet flue gas damper (29) on the inlet flue gas duct (24) and open the outlet flue gas damper (30) on the exhaust flue gas duct (25) when the oven temperature is too high. When the oven temperature is too low, the control panel will open the inlet flue gas damper (29) and close the outlet flue gas damper (30). In both electric heating and flue gas heating, the oven cavity (14) temperature is made more even by circulating the hot air or flue gas through a hot air/gas suction duct (26) through a high temperature fan (23) and blow back the hot air/gas back into the oven through the hot air/gas return duct (27). The temperature inside the oven cavity (14) can be controlled within 500°C but based on actual implementation, the characteristics of the powder coating material has limited the oven cavity (14) temperature to 350°C. The oven (5) includes the base piece (13) of the oven and the top insulated cover (7) of the oven.
The process for an improved powder coating for the internal wall of a duct fitting involves these main steps:
Step 1 : Load the duct fitting into the oven, mounting the duct fitting onto the oven with the first end and second end of the duct fitting attached to the first and second duct attachment pieces. The duct attachment pieces rests on the traction wheels. The rotational speed is then set. The duct fitting is therefore rotating inside the oven, with the turning of the traction wheels, which is driven by the electric motor (19). At the same time, the clamp-down wheels will hold the duct attachment piece in place. The duct fitting is then heated up as it rotates along its longitudinal axis. Step 2: While allowing the continuously heated duct fitting to remain rotating inside the oven, the automatic sprayer is moved along or parallel to the longitudinal axis of the interior of the duct fitting. The automatic sprayer applies the powder coating by spraying onto the internal wall of the duct fitting.
Step 3: After the completion of the spraying process, the duct fitting is allowed to remain inside the oven for the dwell time to elapse so that the powder coating could bake and cure.
For the application of subsequent powder coats, Step 2 is repeated after the completion of Step 3 and this process is iterated depending on the number of coats to be applied. At the end of the entire coating process, the duct fitting is removed from the oven for cooling down.
When performing Step 2, the rotational speed of the duct fitting is adjustable within the range from 6 - 1440 rpm to ensure that powder is evenly sprayed onto the internal wall of the duct fittings.
Depending on the size of the oven, the temperature control is achieved by a PLC controller switching on/off the electrical heater elements or by PLC controller to regulate the hot flue gas supply and exhaust. Before carrying out Step 1 , the top insulated cover of the oven (7) needs to be lifted up to allow the duct fitting (8) to be loaded onto the oven (5), after which the top insulated cover of the oven (7) is lowered down and closed. Both ends of the duct fitting (8) are fastened with the duct attachment piece (9). The electric heating element (12) can then be switched on to heat up the oven cavity (14). The electric heating elements (12) are installed inside the base piece of the oven (13) and these electric heating elements (12) are located close to the duct fitting (8). When the electric heating elements (12) heats up the oven cavity (14), the duct fitting (8) is rotated by the duct attachment pieces (9) and as a result the duct fitting (8) is evenly heated up. When the temperature within the oven cavity (14) reaches the desired set-point value, the spray head (15) of the automatic sprayer (20) is activated to move into the duct fitting (8). The spray head (15) then begins to perform spraying of the powder coating onto the internal walls of the duct fitting (8). hi the process of the spraying, the duct fitting (8) remains rotated by the duct attachment pieces (9) and results in the powder being evenly coated onto the internal walls of the duct fitting (8). While the spray head (15) is performing the spraying process, the automatic sprayer (20) needs to move along or parallel to the longitudinal axis of the duct fitting (8). To facilitate this, a set of guide rails for the automatic sprayer (21) are installed aligned in parallel to the longitudinal axis of the duct attachment piece (9). The automatic sprayer (20) is mounted onto these guide rails (21) and as the automatic sprayer (20) moves along the guide rails (21) driven by the mechanised screw (22), the spray head (15) moves along or parallel to the duct fitting's (8) longitudinal axis into the interior of the duct fitting (8). To prevent the displacement and misalignment of the duct attachment pieces (9) while they are in rotation, the clamp-down wheels (6) are fitted to press down on the external circumferential surfaces of the duct attachment pieces (9). As shown on Fig. 2, fixing brackets for the clamp-down wheels (10) are fitted on the oven frame (4) to both sides of the duct attachment pieces (9) and the clamp-down wheels (6) are fitted to these fixing brackets (10).
Fixed pulleys (1) are fitted to the oven frame (4) and these are fitted with steel cables (2). One end of these steel cables (2) is attached to the fixing brackets for the clamp-down wheels (6) while the other end is attached to the counterweight block (3). As a result of the traction effect in the steel cables (2), the position of clamp-down wheels (6) can be adjusted to suit the different dimension of the duct attachment pieces (9), and consequently different diameters of duct fittings can be fitted into the oven.
Before powder coating is applied, the internal wall of the duct fitting is first heated up with the duct fitting rotating on its longitudinal axis. After the spraying of powder coating onto the internal wall of the duct fitting is completed, it shall remain rotated and heated inside the oven to allow for the dwell time to elapse so that the powder coating could be baked and cured. The system for a duct fitting with improved powder coating includes the supporting frame of the oven and the main body of the oven. The main body of the oven is an enclosure that could accommodate the duct fitting and it includes all parts of the rotational drive mechanism that rotates the duct fitting on its longitudinal axis and the automatic sprayer that performs the spraying of powder coating onto the duct fitting's internal walls.
The automatic sprayer mentioned herein consists of a spray gun head that moves into and out of the oven along its longitudinal axis while the rotational drive mechanism includes the customized duct attachment pieces that are fastened to the duct fitting such that one end of each duct attachment piece is extended into the oven. Fitted to the oven frame are traction wheels and clamp-down wheels whose axes are oriented in parallel to that of the duct attachment pieces. The external circumferential surfaces of the traction wheels and the clamp-down wheels are in contact with the external circumferential surfaces of the duct attachment pieces. The traction wheel is coupled to the power drive mechanism which consisted of an electric motor mounted on the oven frame that is coupled to the traction wheel by a chain-link that is wound onto its output gear shaft.
At the end of each duct attachment piece, there is an adjustable fixing bracket on the oven frame from which the clamp-down wheel is attached. At the top of the oven frame, there is a pulley system that consisted of steel cables with one end attached to the clamp-down wheel fixing bracket and the other end attached to a counterweight block. Mounted on the oven frame is a pair of traction wheels whose axes are aligned on the same horizontal plane. These traction wheels are located below the duct attachment pieces and in contact with the latter's external circumferential surfaces, supporting them above.
Each end of the attachment piece is covered by an insulated cap. On the cap nearer to the spray gun is an opening for the sprayer to access into the inner part of the duct.
When compared to existing processing techniques, the invention described above has several merits as detailed below:
In the course of actual implementation, with the duct attachment pieces fastened to the duct fitting and the entire assembly placed inside the oven, the duct fitting will rotate together with the attachment pieces during operation. While the automatic sprayer performs the spraying of powder coating onto the internal walls of the duct fitting, the fact that the duct fitting still remains inside the continuously heated oven enclosure will ensure that a consistent and stable operating environment so that the powder coating process is maintained. This also meant that spraying and curing can be completed in a single step without the hassle of bringing the duct fitting into and out of the oven repeatedly, cutting down on processing time and improving the production output efficiency. Heating of the oven can be done by means of electric heaters installed within the chamber of the oven, i.e., the space formed by the outside of the duct fitting, the attachment pieces and the oven body. However for bigger ducts, a bigger oven is required and consequently the heat needed for baking and curing is by introducing hot flue gas from burning of LPG or LNG.
As the spraying process is performed while the duct fitting is rotating, the internal wall of the duct fitting is evenly powder coated thus improving the quality of the coated product.
The rotation of the duct fitting also enables the temperature to be more even. In addition, a recirculation system will suck hot air/hot gas from the chamber of the oven and blow back to the 2 ends of the oven.
In the configuration described above, it is found rotating a duct fitting is simpler to attain instead of a rotational mechanism to be fitted onto the spray gun head. The inventor has greatly simplified the design and installation of this customized powder coating equipment.
Although an embodiment of the invention have been described, it should be apparent, however, that various modifications, rearrangements, substitutions alterations and adaptations to those embodiments may occur to persons skilled in the art with the attainment of some or all of the advantages of the present invention. Accordingly, it should be clearly understood that the present invention is not intended to be limited by the particular features and structures hereinbefore described and depicted in the accompanying drawings. It is therefore intended to cover all such modifications, alterations and adaptations without departing from the scope and spirit of the present invention as defined by the appended claims.
ADVANTAGEOUS EFFECTS OF THE INVENTION
The use of a continuously heated oven throughout the stages of the powder coating process will ensure that a consistent and stable operating environment so that spraying and curing can be completed in a single step without the hassle of bringing the duct fitting into and out of the oven repeatedly, cutting down on processing time and improving production output efficiency.
As the spraying process is performed while the duct fitting is rotating, the internal wall of the duct fitting is evenly powder coated thus improving the quality of the coated product.
The spraying of layers of powder coating onto the internal walls of a duct fitting while enclosed inside the continuously heated oven would also reduce energy consumption and powder coating since the duct fitting remains inside the oven throughout the process.

Claims

1. A system for improved powder coating of the internal walls of a duct fitting, the duct fitting having a first end and a second end, the system comprising:- an oven, the oven comprising a base and a removable top insulated cover with an oven cavity formed therein; duct attachment means; a drive mechanism; heating means; and an automatic powder coating sprayer; characterized in that the first end and second end of the duct fitting is attached to each end of the oven by the attachment means and placed within the oven cavity, the automatic powder coating sprayer applying a first powder coating to the internal walls of the said duct fitting, which is continuously rotated by the drive mechanism, so that a first powder coating is applied evenly throughout the internal walls of the said duct fitting, while being heated continuously by the heating means, so that the first powder coating is baked and cured, followed by application and heating of additional layers of powder coating to the internal walls of the duct fitting, so that the each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder coating resulting in an improved powder coating for the duct fitting.
2. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein the top insulated cover of the oven is removable to allow the duct fitting to be placed onto the base of the oven, said duct fitting secured within the oven cavity by the duct attachment means.
3. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein the drive mechanism consists of an electric motor, a clamp down wheel and at least two traction wheels, for rotation of the duct fitting, the first and second end of which are attached to the duct attachment means.
4. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein the duct attachment means consists of a collar for each end of the duct fitting, to secure the duct fitting within the cavity where the temperature is more even and also act to cut off powder coating from reaching the top insulated cover and base of the oven.
5. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein the duct attachment means is a grip for each end of the duct fitting, to secure the duct fitting onto the oven.
6. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1 , wherein the heating means consist of a plurality of electrical elements in the oven.
7. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1 , wherein the heating means consist of a plurality of gas burners in the oven.
8. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1 further comprising a PLC controller to control the drive mechanism, to start and control movement of the automatic powder coating sprayer and to regulate the baking and curing temperature range throughout the application, baking and curing of powder coatings on the internal walls of the duct fittings.
9. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1 wherein the baking temperature of the oven is from 250 0C to 350 0C.
10. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1 wherein the curing temperature range of the oven is from 270 0C to 300 0C.
11. The PLC controller for the system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 8 further comprising a plurality of temperature sensors which turns on or turns off the electric heaters to regulate the baking and curing temperature range and by releasing or keeping heat within the oven and also to improve the circulation of heat within the oven.
12. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1 further comprising a plurality of hot flue gas inlets and outlets wherein at slow starting temperature, the temperature sensors will sense the oven temperature is below the baking temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to raise the temperature in the oven and if the oven temperature is over the baking and curing temperature range, the controller will open the inlet flue gas damper and close the outlet flue gas damper to lower the temperature in the oven.
13. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1, further comprising a high temperature fan and hot air/gas suction duct for re-circulation of hot air within the oven so that all parts of the oven can be maintained at an even baking and curing temperature range.
14. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein the automatic powder coating sprayer has a spray head and is mounted on a set of guide rails, which are laid parallel to the longitudinal axis of the duct fitting, the spray head movable by the electric motor of the drive mechanism along the length of the internal walls of the duct fitting to spray powder coating onto the entire internal walls of the duct fitting.
15. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, wherein automatic powder coating sprayer will be activated by the controller and move into the internal of the duct to perform spraying of powder coating when the temperature of the oven is within the baking temperature range.
16. The system for improved powder coating of the internal walls of a duct fitting as claimed in Claim 1 further comprising an oven frame and a pulley system to open the oven for mounting of the duct fitting and for mounting the duct attachment means.
17. The oven frame as claimed in Claim 14 further comprising an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel.
18. The pulley system as claimed in Claim 14 wherein the pulley system is fitted to the oven frame and consists of fixed pulleys, with steel cables attached at one end to the clamp down wheels and at the other end attached to a counter weight block.
19. The system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1 , wherein the rotation speed of the duct fittings is from 6 rpm to 1440 rpm.
20. An improved powder coating process for the internal walls of a duct fitting, using the system for improved powder coating of the internal walls of a duct fitting, as claimed in Claim 1, comprising these steps:- attaching a first and second end of the duct fitting to duct attachment means; loading and enclosing the duct fitting complete with the end attachments in an oven cavity of an oven; using the heating means to heat the duct fitting until the temperature reaches baking temperature range; whereupon the automatic powder coating sprayer will move into oven and along the horizontal axis of the duct fitting; said drive mechanism rotating the duct fitting so that the sprayer will spray a first layer of powder coating evenly onto all areas of the internal wall of the duct fitting; said powder coating being heated continuously by the heating means so that the first layer of powder coating is baked and cured, followed by application and heating of one or more additional layers of powder coating to the internal walls of the duct fitting, so that each additional layer of powder coating is baked and cured, until the duct fitting has one or more layers of powder coating resulting in an improved powder coating for the duct fitting.
21. An improved powder coating process of the internal walls of a duct fitting, as claimed in Claim 20 further comprising a step of clamping the duct attachment means to the duct fitting, said duct attachment means held by an adjustable fixing bracket on the oven frame, said adjustable fitting bracket fitted with clamp down wheel wherein when the duct fitting is rotated, said clamp down wheel will position the rotation of the duct attachment means so that the duct fitting is rotated along the same longitudinal axis.
22. An improved powder coating process as claimed in Claim 20, comprising the additional steps of controlling the heat inside the oven cavity to ensure a consistent and stable operating environment for the powder coating process, while the powder coating is baked and cured to form a first layer on the internal walls of the duct fitting, followed by additional layers of powder coating, by turning on or turning off the electrical power supply to one or more of the electrical heater elements or by regulating the hot flue gas supply and exhaust, depending on the size of the oven, opening the inlet flue gas damper and closing the flue gas outlet damper when the temperature is below the baking and curing range, closing the inlet flue gas damper and opening the flue gas outlet damper when the temperature is over the baking and curing range, and re-circulating the hot air or flue gas during the entire heating, baking and curing process.
PCT/SG2007/000249 2006-08-15 2007-08-13 System for improved powder coating of duct fittings and process for same WO2008020812A1 (en)

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JP2015171682A (en) * 2014-03-12 2015-10-01 株式会社栗本鐵工所 inner surface heating method of cast iron pipe
CN107702446A (en) * 2017-09-21 2018-02-16 天津市弘亚润滑粉制造有限公司 A kind of drying unit
CN108970858A (en) * 2018-08-22 2018-12-11 新兴铸管股份有限公司 A kind of steel pipe spray painting anti-corrosive apparatus
CN108970858B (en) * 2018-08-22 2023-10-03 新兴铸管股份有限公司 Steel pipe paint spraying anti-corrosion device
CN112156932A (en) * 2020-11-04 2021-01-01 吉林大学 Temperature control spraying device for preparing large-scale rotation body bionic microstructure resistance reduction surface
CN115069463A (en) * 2021-03-15 2022-09-20 日本碍子株式会社 Method for manufacturing cylindrical member for exhaust gas treatment device, and coating film forming apparatus
CN115233217A (en) * 2022-07-25 2022-10-25 江苏大学 Device and method for cladding coating on micro inner hole by global transient heating
CN115233217B (en) * 2022-07-25 2024-01-05 江苏大学 Device and method for global transient heating micro-inner hole cladding coating
CN115445884A (en) * 2022-09-20 2022-12-09 三联泵业股份有限公司 Processing method of efficient double-suction pump
CN115445884B (en) * 2022-09-20 2023-07-21 三联泵业股份有限公司 Processing method of efficient double-suction pump
CN117046691A (en) * 2023-10-12 2023-11-14 潍坊天德管业有限公司 Plastic coating equipment for producing plastic coated steel pipes
CN117046691B (en) * 2023-10-12 2023-12-08 潍坊天德管业有限公司 Plastic coating equipment for producing plastic coated steel pipes

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