Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F26—DRYING
  • F26B—DRYING SOLID MATERIALS OR OBJECTS BY REMOVING LIQUID THEREFROM
  • F26B3/00—Drying solid materials or objects by processes involving the application of heat
  • F26B3/28—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun
  • F26B3/283—Drying solid materials or objects by processes involving the application of heat by radiation, e.g. from the sun in combination with convection
• • 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
  • B05D3/0209—Multistage 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
  • 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
  • B05D3/0254—After-treatment
  • B05D3/0263—After-treatment with IR heaters
• • 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
  • B05D3/04—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 exposure to gases
  • B05D3/0406—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 exposure to gases the gas being air
  • B05D3/0413—Heating with air

Definitions

• the invention relates to a method for drying coated workpieces by infrared radiation and a device for carrying out the method.
• the invention can be used particularly advantageously for gelling (drying) powder-coated castings, in particular also of gray castings, also with an irregular shape.
• the invention can also be advantageous in the case of thin-walled workpieces of complicated configuration, among others. made of sheet metal.
• the workpieces can also be coated by an electrostatic, water-soluble or solvent-containing lacquer. Coated workpieces made of ceramic or glass can also be dried.
• a furnace is known from US Pat. No. 2,419,643, in the housing of which infrared radiators with reflectors are arranged at a distance from the housing walls.
• the infrared emitters enclose a radiation room.
• the housing has inlet and outlet openings and a means of transport for transporting the workpieces through the housing. After entering the housing, the workpieces arrive in a zone in which the infrared radiators are arranged close to one another are, so that the workpieces are quickly heated to the desired drying temperature by the intensive direct radiation.
• the drying temperature only needs to be maintained, for which a smaller number of emitters is sufficient, so that the oven has a second zone with infrared emitters arranged at a greater distance from one another than is the case in the first heating zone .
• a suction device e.g. also to remove vapors generated during drying to extract air.
• coated castings of irregular shape cannot be dried or treated in such furnaces, since burns of the coating on the protruding parts on the one hand and insufficient drying or treatment results for undercuts and in the shadow of the IR rays on the other hand lying areas can be observed.
• the convective heat portion is passed on to the atmosphere completely unused.
• the object of the invention is to provide a method by means of which workpieces - in particular also workpieces coated with powder, but also with liquid lacquers - can also be dried with an irregular shape and with undercuts by IR radiation.
• the object of the invention is also to provide an economical device for carrying out the method.
• the problem is solved i by a method with the features of claim 1.
• the workpieces are heated by the radiation, which is cooled by the circulated air projecting parts - which excludes overheating ⁇ and parts that are only irradiated to a lesser extent and thus can absorb less radiation energy are heated.
• heat compensation takes place within the workpieces, which is intensified by the flow flowing around the workpieces in this zone as well. Due to the heat balance within the workpieces, the places in the radiation shadow that absorb less radiation energy are supplied with the required heat energy for drying and the energy used is used more economically. Due to the air circulation, the reflectors of the radiators and the housing walls can also be cooled and the heat absorbed can be used to treat the workpieces, which saves energy.
• Maintaining a negative pressure enables the desired flow conditions to be maintained for washing around the workpieces and prevents e.g. Dust particles of a powder coating can escape to the outside.
• the diffuse infrared radiation distribution and the "bil arfect" achieved thereby also enable undercuts and depressions to be reached and concentrations on certain projecting parts to be prevented, thus contributing to more uniform heating on all sides.
• FIG. 1 is a schematic representation of a longitudinal section through a device according to the invention
• FIG. 2 in cal ati cal representation of a section through the device of FIG. 1 along the line II-II
• the device has a known, tubular, tubular housing 1, which has an inlet or outlet opening 2, 3 on the end faces.
• a transport means 4 is guided through the inlet and outlet opening 2, 3 and the housing 1, with which workpieces 5 coated with a lacquer can be transported through the device.
• the interior of the housing 1 is longitudinally divided into three interconnected zones 6, 7, 8, a preheating, a resting and a post-heating zone.
• the preheating zone 6 can be longer, since this is where the workpieces are heated to the working temperature, or can also be of the same length as the reheating zone 8.
• a ratio of the zones 6, 7, 8 to one another would be, for example, 2: 2: 1, 2: 1: 1 or 2: 1: 2 or also 1: 1: 1.
• housings 1 can be arranged inside the housing 1 (not shown) or in separate housings 1 * Cin .Fig. 1 indicated) can be arranged. These housings 1 "can also be designed to be movable.
• the work squerschni tt which depends on the dimensions of the respective workpieces 5
• enveloping reflectors 9 are arranged, which extend parallel to the transport direction.
• the reflectors 9 are arranged at least at a distance from the workpiece 5, but preferably also angularly adjustable, and form the walls of the actual irradiation rooms.
• a plurality of reflectors 9 can be connected to form reflector walls 10, 10 'and together distance-adjustable
• shape of the reflector envelope and thus the cross section of the irradiation rooms depend on the shape of the workpieces 5 and should adapt to their envelopes.
• Right-angled arrangements of the reflector walls 10, 10 * are possible. Because of the better adaptability to different workpieces 5 and in terms of better diffuse beam distribution, arrangements in the form of a hexagon as in the exemplary embodiment, or a triangle, pentagon, etc. preferable.
• the lateral reflector walls 10 are arranged in parallel and the upper and lower reflector walls 10 * are movable about an axis 11. If necessary, the walls 10 can also be arranged in parallel and at the same time pivoted, so that arrangements in pyramid form are possible.
• the reflectors 9 are at a - preferably adjustable - side distance from one another, so that there are passage gaps between them, connected to the reflector walls 10, for example they are arranged on supports 12 so as to be displaceable and detachable, arrestable and removable.
• the active side of the reflectors 9 is directed towards the workpieces 5 and consists of a high-gloss layer, for example anodized aluminum, and is preferably spatially structured, for example by means of pyramids with a regular or irregular three-, four-, five-, hexagonal, etc. base .
• the reflectors 9 have the task of diffusely distributing the rays from IR emitters 13 in the irradiation room; they should under no circumstances focus them.
• the infrared radiators 13 are arranged in the central axis of individual or all reflectors 9. Between the inner wall 14 of the housing 1, the side walls of the quiet zone 7 and the rear sides of the reflectors 9, there are 10 channels 15 of different volumes depending on the position of the reflector walls.
• the walls of the channels 15 are aerodynamically shaped in order to ensure a uniform, preferably vortex-free laminar flow in the channels 15.
• the right-hand and left-hand channels 15 are separated from one another in the upper region by partitions 16 surrounding the transport means 4. In the lower area they open into a common pressure chamber 17 which is covered towards the channels 15 by plates 18 or grids which have openings.
• the channels 15 on the right and left sides can also be completely separated from one another in the lower region, the pressure chamber 17 being integrated.
• the plates 18 or grids can also be dispensed with.
• suction openings 19 of a ventilator 20 are executed.
• the pressure side of the fan 20 is connected to the pressure chambers 17 of the preheating zone 6 and the post-heating zone 8.
• the channels 15 have, in the upper closed part between the partition 16 and the housing side wall, provided with throttles of exhaust air nozzles 21, which can be used to regulate the temperature of the atmosphere inside the device and, if appropriate, to extract vapors.
• the inner wall of the furnace behind is protected from direct radiation protected and due to the generated flow conditions, they are also cooled. Due to the flow conditions achieved inside, the reflectors are also protected against the deposition of cracked and cracked products.
• this wall can consist of a high-gloss layer, for example anodized aluminum, and can also be spatially structured.
• the infrared effect from the housing causes vagabonding infrared rays to be directed back onto the workpiece and, in conjunction with the air flow in the housing, this avoids any appreciable heating of the wall, which makes special insulation unnecessary.
• the distance between the reflectors 9 and the reflector walls 10, 10 ' is set in accordance with the size of the workpiece 5 to be treated and the optimum effective distance of the IR radiators 13 used.
• the number, the distribution and the type of infrared radiators 13 are selected in accordance with the shape and nature of the workpiece 5 and the coating and the amount of heat required as a function thereof, and the distance between the reflectors 9 from one another is also selected accordingly. If the same or similar items are always subjected to the treatment, this setting is only made once during commissioning. Mid-length infrared emitters with a wavelength of ⁇ 2 to 3 have proven particularly useful. Then some or all of the IR emitters 13 provided - with reduced power - and the fan 20 are switched on.
• the idle temperature required in each case is set in the device.
• the arrangement of the fan 20 described results in a vacuum in the quiet zone 7 and also in the irradiation rooms of the preheating and post-heating zones 6, 8, while an overpressure builds up in the channels 15.
• This forms a flow out of the channels 15, which flows around the reflectors 9 into the radiation chambers and around the workpieces 5 into the rest zone 7.
• the reflectors 9 are cooled by this flow and some of the convective heat is obtained for the treatment of the workpieces 5.
• the flow movement is indicated by arrows in the figures.
• the IR emitters 13, controlled by a pilot lamp are raised and reach their normal output when the workpiece 5 enters the radiation chamber of the preheating zone 6. Due to the type and arrangement of the reflectors 9, the radiation from the IR emitters 13 is diffusely distributed in the irradiation space and thus also partially reflected by other reflectors 9 before they reach the workpiece 5. These reflections can also be used to achieve undercuts and depressions which would lie in the shade in the case of a straight-line beam path. A more uniform heating is achieved by the above-mentioned flow around. The workpiece 5 then reaches the rest zone 7 without an IR radiator.
• a device of the type described was equipped with medium-wave twin-tube IR quartz beams with an eight-shaped cross-section and a gold-coated back and reflectors with a spatially structured refector surface made of high-gloss anodized aluminum.
• the side distance between the neighboring reflectors was 15 mm, that between the central axes of the IR emitters was 65 mm.
• the area power of the emitters was between 30 and 36 kW / m.
• the idle power was 10% of the installed power.
• Powder-coated casting workpieces (for example made of gray cast iron), partly with complicated shapes, were passed through the device at a speed of 1 m / min without rotation of the workpieces. In the concrete example, the workpieces remained in the preheating zone for 2 minutes, in the rest zone for 1 minute and in the heating zone for 1 to 1.5 minutes. After 2 minutes, melting of the powder was observed on the sides directly facing the emitters. At this moment the rest zone should be reached.
• the temperature in the preheating zone and the post-heating zone was limited to 200 ° C.
• air can also be discharged through the exhaust air connection 21, which requires a stronger suction of ambient air through the inlet or outlet openings 2, 3.
• a low negative pressure of approximately 10 Pa was maintained in the radiation treatment rooms and in the rest zone 7, and a slight positive pressure of 500 Pa was maintained in the channels 15.
• the flow achieved and the omission of the IR emitters resulted in approx.
• the coated workpieces 5 After exiting the device and cooling, the coated workpieces 5 had uniformly gelled, high-quality coatings.
• Gray cast iron - " with an irregular shape are suitable, a total dwell time of 40 to 45 minutes is required for the same workpieces.

Landscapes

• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Microbiology (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Drying Of Solid Materials (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Coating Apparatus (AREA)
• Processing And Handling Of Plastics And Other Materials For Molding In General (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=6228759

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Family Applications Before (1)

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• 1984
  • 1984-02-24 DE DE3406789A patent/DE3406789C1/de not_active Expired
• 1985
  • 1985-02-22 WO PCT/EP1985/000066 patent/WO1985003766A1/de not_active Application Discontinuation
  • 1985-02-22 EP EP85101940A patent/EP0154265B1/de not_active Expired
  • 1985-02-22 JP JP60501167A patent/JPS61501082A/ja active Granted
  • 1985-02-22 ZA ZA851351A patent/ZA851351B/xx unknown
  • 1985-02-22 DE DE8585101940T patent/DE3562824D1/de not_active Expired
  • 1985-02-22 CA CA000474946A patent/CA1230273A/en not_active Expired
  • 1985-02-22 EP EP85901406A patent/EP0174351A1/de active Pending
  • 1985-02-22 US US06/793,691 patent/US4665626A/en not_active Expired - Fee Related
  • 1985-02-22 AT AT85101940T patent/ATE34457T1/de not_active IP Right Cessation
  • 1985-02-23 ES ES540666A patent/ES8607524A1/es not_active Expired
  • 1985-02-25 IN IN138/CAL/85A patent/IN162813B/en unknown
  • 1985-10-23 DK DK486285A patent/DK161608C/da not_active IP Right Cessation
  • 1985-10-23 NO NO85854240A patent/NO161193C/no unknown

Non-Patent Citations (1)

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