Vacuum coating apparatus

Abstract: The vacuum coating apparatus comprises a chamber (91), an evacuating device (92), a fluid supplier (93), a hood (1) and a gas reservoir (2). During operation, the chamber is subjected to a partial vacuum by the evacuating device (92) and filled with treatment fluid. At this time, air at predetermined temperature supplied from the gas reservoir (2) is admitted into the chamber (91). As a result, the temperature and viscosity of the treatment fluid in the chamber (91) become constant. The material (8) to be treated is, then, fed into the chamber (91) via an inlet port (911) and an outlet port (912). An air flow caused by evacuation removes excess fluid on the material (8) at the outlet port (912), resulting in evenly forming a thin coating film.

Description: The present invention relates to a vacuum coating apparatus for forming a thin layer coating film of treatment fluids such as paints over the surface of a material with a long body, i.e., wood, to be treated. Description of the Related Arts As a coating apparatus for forming the thin layer coating film over the material to be coated, a brush, spray, roll coater, curtain coater, dip coater, blade coater, and the like are well known. When applying treatment fluids over the material surface, however, such known apparatus often causes the mist or gas of the treatment fluid to scatter around. Moreover depending on the type of such coating apparatus in use, special skill for the fluid application is required. In order to solve the above problem, the vacuum coating apparatus for wood treatment has been invented (GB2145442B). As FIGURE 4 shows, the apparatus has a chamber 91 through which a material 8 is passed via an inlet port 911 and an outlet port 912, an evacuating device 92 by which the chamber 91 is subjected to a partial vacuum, and a fluid supplier 93 from which treatment fluid 7 is supplied to the chamber 91. The material 8 is continuously fed into the chamber 91 through the inlet port 911 to be drawn out thereof through the outlet port 912. At this time, the chamber 91 is kept subjected to a partial vacuum by the evacuating device 92 so that the treatment fluid 7 is supplied into the chamber 91 from the fluid supplier 93. This causes air to flow into the chamber 91 via the clearances at the inlet port 911 and outlet port 912, resulting in an air flow 910 over the surface of the material 8. The air flow 910 removes excess fluid from the material 8 to have a thin layer coating film evenly formed over the surface thereof. The apparatus of the above type is so constructed to form the thin layer coating film over the material surface at high speed. The apparatus also prevents the fluid mist from scattering and requires no special skill for the fluid application. In FIGURE 4, reference numerals 921, 922 designate exhaust passages, 931 and 94 designate a fluid passage, and roller guides, respectively. With the apparatus of the known type, however, it is difficult to ensure to have the coating film thin and evenly applied over the material surface without lowering productivity and independent of the type of the treatment fluid in use, and change in the environmental temperature. When treating the material, particularly wood, the thickness of the film to be coated thereon is often required to be 30 µm or less in order to accentuate its natural grain. For such a treatment, substantially a thin film is formed over the wood surface only without filling the naturally formed vessel in the wood with the fluid. In case of coating the film to have relatively a large thickness, crack occurs in the film surface. Or in such a case, processing, i.e., cutting and nailing, the wood that has been treated with the fluid might also cause the film to be cracked. A thin film can be formed over the material surface by decreasing the speed for feeding the material in the chamber. This method, however, considerably deteriorates the productivity. When using a paint either of water-based nature or ultraviolet curing type as the treatment fluid in an apparatus of the known type, the film with desired thickness cannot be obtained in spite of decreasing the feeding speed. In case of using the ultraviolet curing paint, the viscosity of oligomer, a component thereof, cannot be lowered easily, preventing to sufficiently reduce the viscosity of the paint. Generally as TABLE 2 shows, the viscosity of the treatment fluid is likely to vary with the temperature. The treatment fluid, thus, should be kept at predetermined temperature during coating. In the known apparatus, since outside air is admitted into the chamber through the inlet port and outlet port, the temperature in the chamber is likely to vary with the outside air temperature. Temperatures in the chamber in summer and winter, or early in the morning and daytime, thus, become different. This change leads to influence the viscosity of the fluid, preventing to have the thin layer coating film evenly formed over the material surface. SUMMARY OF THE INVENTION An object of the present invention is to provide a vacuum coating apparatus enabling to form a thin coating film with even thickness over the surface of a material with a long body and to increase productivity independent of the type of the treatment fluid and change in the environmental temperature. A vacuum coating apparatus of the present invention includes a chamber provided with an inlet port and an outlet port through which a material to be treated is fed, an evacuating device for subjecting the chamber to a partial vacuum, a fluid supplier for supplying a treatment fluid to the chamber, a hood for covering the inlet port and outlet port of the chamber, and a gas reservoir for supplying gas at constant temperature to the hood. Other features and advantages of this invention will be apparent from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a schematic explanatory view of a first embodiment of a vacuum coating apparatus. FIGURE 2 is a perspective view of the first embodiment of the vacuum coating apparatus. FIGURE 3 is a schematic explanatory view of a second embodiment of the vacuum coating apparatus. FIGURE 4 is a schematic explanatory view of a coating apparatus of a known type. DETAILED DESCRIPTION OF THE INVENTION The most salient feature of the present invention is to provide a hood and a gas reservoir with a vacuum coating apparatus, by which the gas at predetermined temperature is admitted into a chamber to keep viscosity of the treatment fluid therein constant. The apparatus of the present invention is used for coating a long material such as a carbon shaft of a golf club and a construction material. The material may be formed of either wood, plastic, or carbon. The apparatus becomes the most efficient when it is used for coating the wood so as to accentuate its natural grain. The above treatment fluids may be paints, stains, antiseptic agents, moth-proofing agents, adhesives, bleachers, or the mixture thereof. For example, the paints may be of either water-based nature, emulsion, or ultraviolet curing type. The apparatus according to the present invention is advantageous in forming the thin layer coating film by means of those fluids, particularly, a water-based and solventless treatment fluids. The above gas may be air or inert gas, such as nitrogen, argon, carbon dioxide gases, and mixture thereof. A blower may be used as the evacuating device. As the gas reservoir for supplying the gas at predetermined temperature, it may be so constructed to supply cold or hot water controlled to a desired temperature from a cooling/heating device as a water temperature controlling device to a heat exchanger, by which the gas passing therethrough is kept to be at the desired temperature as FIGURE 1 shows. Preferably the gas reservoir is communicated with a temperature sensor so as to control the temperature of the gas reservoir based on the signal from the temperature sensor. This enables to have accurate adjustment of the treatment fluid temperature in the chamber. As FIGURE 1 shows, as the first method for supplying the gas, unused gas is passed through the gas reservoir to be supplied to the hood. As FIGURE 3 shows, as the second method, the gas that has been already used in the chamber is recycled to the gas reservoir from the evacuating device. Employing the second method enables to re-use the treatment fluid, solvent and heat, and to prevent the fluid and solvent from leaking out. In the present invention, when coating the material, the chamber is subjected to a partial vacuum by means of the evacuating device. Then the treatment fluid is supplied into the chamber from the fluid supplier, while the material to be treated is continuously fed into the inlet port of the chamber. The material passes through the chamber to leave from the outlet port thereof. The treatment fluid is applied over the material surface when it passes through the chamber. The air is caused to flow into the chamber via the clearances between the inlet and outlet ports, and the material. The resulting air flow in the outlet port removes excess fluid from the material surface. In the present invention, the gas at predetermined temperature is supplied from the gas reservoir to the hood. The gas within the hood is admitted into the chamber through the inlet port and outlet port, resulting in predetermined temperature of the treatment fluid in the chamber. The predetermined temperature of the fluid leads to keep its viscosity constant. As a result, at the outlet port of the chamber, the apparatus provides the material treated with substantially a thin coating film that has been evened out. As aforementioned, since the viscosity of the treatment fluid is controlled by means of the gas at constant predetermined temperature supplied from the gas reservoir, the speed for feeding the material can be increased as well as improving the productivity. The present invention, thus, provides a vacuum coating apparatus enabling to form substantially a thin coating layer over the material to be treated regardless of the type of the treatment fluids, and the change in environmental temperature, resulting in improving the productivity. DESCRIPTION OF THE PREFERRED EMBODIMENT EMBODIMENT 1 A vacuum coating apparatus according to a first embodiment of the present invention will be described referring to FIGURES 1 and 2. The vacuum coating apparatus of this embodiment includes a chamber 91 provided with an inlet port 911 and an outlet port 912 through which a material 8 passes, an evacuating device 92 for subjecting the chamber 91 to a continuous partial vacuum, a fluid supplier 93 from which treatment fluid 7 is supplied into the chamber 91, a hood 1 by which those inlet port 911 and outlet port 912 of the chamber 91 are enclosed, and a gas reservoir 2 from which the gas at predetermined temperature is supplied to the hood 1. The hood 1 provided around the inlet port 911 and the outlet port 912 respectively defines openings 10 through which the material 8 is inserted. As FIGURE 1 shows, the gas reservoir 2 is composed of a casing 21, a heat exchanger 22 enclosed in the casing 21, a cooling/heating device 23 as a water temperature controlling device for supplying either cold or hot water to the heat exchanger 22, and a controller 24 for controlling the cooling/heating device 23. The casing 21 has a hole 210 on its top for admitting the outside air. It is communicated with the upper part of the hood 1 via a gas passage 26. The cooling/heating device 23 has a heater and a refrigeration circuit for heating or cooling water so as to circulate either hot or cold water to the heat exchanger 22. A controller 24 is connected to a temperature sensor 25 disposed within the chamber 91. The temperature sensor 25 detects the temperature of the treatment fluid 7 in the chamber 91. The controller 24 is so programmed to control the cooling/heating device 23 to set a desired temperature upon receiving the signal from the temperature sensor 25. The chamber 91 is removably provided with templates 311 by means of a guide 312. Either the inlet port 911 or outlet port 912 has templates 311 formed therein. Each section of those inlet and outlet ports 911 and 912 is so shaped to have the same section as, but larger area than that of the material 8. As FIGURES 1 and 2 show, the bottom part of the chamber 91 is communicated with the fluid supplier 93 via a drain pipe 341 provided with a valve 342. The valve 342 can be opened and closed by a cylinder 343 connected thereto. In FIGURE 1, reference numerals 321, 322, 33 and 923 designate a buffer plate, a baffle, a pump, and an exhaust port, respectively. In FIGURE 2, the reference numeral 35 designates a conveyer. Other constructions are the same as those of the known apparatus. When applying the treatment fluids, the material 8 to be treated is ground on its surface. Then it is set on the conveyer 35. While the fluid supplier 93 is filled with the treatment fluid 7. In this embodiment, a paint is used as the treatment fluid 7. The pressure in the chamber 91 is reduced down to be in the range of 50 to 150 mmHg (66,5 to 200 mbar) by means of the evacuating device 92. The chamber 91 is continued to be further subjected to a vacuum. The treatment fluid 7 is supplied into the chamber 91 from the fluid supplier 93, while the material 8 is continuously fed toward the inlet port 911 of the chamber 91. The material 8 passes through the chamber 91 to leave out of the outlet port 912 of the chamber 91. The treatment fluid 7 is applied on the surface of the material 8 passing through the chamber 91. At this time, the air in the hood 1 flows into the chamber 91 via the clearance between the outlet port 912 and the material 8. The resulting air flow 20 removes excess fluid 7 from the surface of the material 8. In this embodiment, the air flow 20 adjusted to be at a predetermined temperature is supplied into the hood 1 from the gas reservoir 2. The controller 24 of the gas reservoir 2 sends the control signal to the cooling/heating device 23 as a water temperature controlling device upon receiving the output signal of the temperature sensor 25 in the chamber 91. The cooling/heating device 23 supplies water controlled to be at desired temperature into the heat exchanger 22 upon receiving the above control signal. By this, the air in the casing 21 is controlled to a predetermined constant temperature, and sent into the hood 1 through the gas passage 26 to be admitted into the chamber 91 therefrom. The treatment fluid 7 in the chamber 91, thus, has a predetermined constant temperature, resulting in constant viscosity. As a result, substantially a thin coating film with even thickness can be formed on the material 8. Since the viscosity of the treatment fluid 7 can be controlled by means of the air at predetermined temperature supplied from the gas reservoir 2, the thin coating film evenly coated can be formed on the material 8 independent of the type of the treatment fluid in use, and the change in the environmental temperature. This embodiment ensures to form substantially a thin coating film on the surface of the material 8. Particularly in case of coating wood, the apparatus according to the present invention is effective for accentuating its natural grain. The thin coating film is formed by controlling the viscosity of the treatment fluid without decreasing the speed for feeding the material through the chamber, resulting in improving the productivity. Repeating the above process step three times will effectively replace the conventional process steps of priming coating, brown coating, and skim coating. EMBODIMENT 2 A vacuum coating apparatus according to this embodiment will be described referring to FIGURE 3. In this embodiment, the casing 21 of the gas reservoir 2 and the evacuating device 92 described in EMBODIMENT 1 are connected via a gas circulation passage 41. Other constructions are the same as those of EMBODIMENT 1. Since the apparatus of this embodiment is constructed as above, similar effects as those of EMBODIMENT 1 can be obtained. The air that has been already used in the chamber 91 is recycled to the gas reservoir 2 by means of the evacuating device 92 through the gas circulation passage 41. This enables to re-use the treatment fluid, solvent and heat, resulting in saving coating cost and preventing the fluid and solvent from leaking. EMBODIMENT 3 This embodiment shows the test data of measurements conducted with respect to the relation between the temperature in the chamber and coating film thickness when using the vacuum coating apparatus according to the aforementioned EMBODIMENT 1. As TABLE 1 shows, the coating film thickness was measured at the respective temperature in the range of 20 to 40 o C. For those measurements, an electromagnetic device for measuring the film thickness is used. Temperature in chamber (°C) Film thickness (µm) 20 26 25 23 30 19 35 17 40 16 As TABLE 2 shows, the viscosity of the treatment fluid was measured at the respective fluid temperature in the range of 15 to 50 o C. For the paint, the ultraviolet curing urethane acrylic resin paint is used through Fordcup No. 4 measurement method. Temperature (°C) Viscosity (S) 15 75 20 58 25 45 30 36 35 29 40 24 45 20 50 18 As TABLE 1 shows, increasing the temperature in the chamber reduces the thickness of the coating film formed on the material surface. This is because, as TABLE 2 shows, viscosity of the paint is gradually reduced as its temperature is increased. Those results show that constant temperature in the chamber will keep the film thickness even. The thin coating film with a desired even thickness can be formed over the material surface by keeping a predetermined temperature in the chamber by means of a controller of a gas reservoir. While the invention has been described with reference to the example, it is to be understood that modifications or variations may be easily made by a person of ordinary skill in the art without departing from the scope of this invention which is defined by the appended claims.

Claims: A vacuum coating apparatus comprising: a chamber (91) provided with an inlet port (911) and an outlet port (912) through which a material (8) to be treated is fed; an evacuating device (92) for subjecting said chamber (91) to a partial vacuum; a fluid supplier (93) for supplying a treatment fluid (7) to said chamber (91); a hood (1) for covering said inlet port (911) and outlet port (912) of said chamber (91); and a gas reservoir (2) for supplying gas at predetermined temperature to said hood (1). A vacuum coating apparatus according to claim 1, wherein said gas reservoir (2) has a heat exchanger (22) for heating and cooling gas to be supplied to said hood (1), and a controller (24) for controlling temperature of said gas. A vacuum coating apparatus according to claim 2, wherein said controller (24) has a temperature sensor (25) for detecting temperature of treatment fluid in said chamber (91). A vacuum coating apparatus according to claim 1, wherein said gas reservoir has a water temperature controlling device (23) for supplying water controlled to be at desired temperature into said heat exchanger (22). A vacuum coating apparatus according to claim 1, wherein gas passages (26) are defined between said evacuating device (92) and said gas reservoir (2). A vacuum coating apparatus according to claim 1, wherein said chamber (91) has templates (311) at said inlet port (911) and outlet port (912) through which said material (8) is fed, and said templates (311) have openings through which said material (8) is fed with their sections equally shaped to those of said material but different sizes. A vacuum coating apparatus according to claim 1, wherein said material (8) is selected from a group consisting of wood, plastic and carbon. A vacuum coating apparatus according to claim 1, wherein said treatment fluid (7) is selected from a group consisting of paints, stains, anti-septic agents, moth-proofing agents, adhesives, bleachers and mixture thereof. A vacuum coating apparatus according to claim 1, wherein said paint is selected from a group consisting of a water-based paint, emulsion paint and ultraviolet curing paint. A vacuum coating apparatus according to claim 1, wherein said gas to be supplied to said hood is selected from a group consisting of air, nitrogen gas, argon gas, carbon dioxide gas and mixture thereof.

Inventors: EBI TADAMICHI, IMAI YOSHIHIKO, EBI, TADAMICHI, IMAI, YOSHIHIKO
Applicants: GEN GEN CHEMICAL IND, GEN GEN CORPORATION
Application year: 1992
Main classification: B27K3
IPC codes: B05C3, B05C15, B27K3