Patent Publication Number: US-6666136-B2

Title: Paper-feed roller and fabrication method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Korean Patent Application No. 2001-73960, filed Nov. 26, 2001 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a paper-feed roller, which is employed in an office automation machine, such as a photocopier, a printer, a facsimile machine, etc, to supply and discharge to-be-copied or to-be-printed paper (herein below called ‘paper’), and a fabrication method thereof, and more particularly, to a paper-feed roller and a fabrication method of producing the paper-feed roller with an economical effect in a fabrication cost and preventing a slippage of paper or a paper jam that is caused by a heat distortion and an abrasion occurring on a surface of a long time operated paper-feed roller. 
     2. Description of the Related Art 
     Generally, an office automation machine, such as a photocopier, a printer, a facsimile machine, etc, has been expected to print an image on a sheet of paper at a higher speed. Accordingly, a paper feed roller employed in the office automation machine is required to supply, convey, and discharge the paper at the higher speed while performing a basic function of preventing slipping of the paper or a paper jam. 
     FIG. 1 shows a general paper-feed roller  10 . The paper-feed roller  10  includes a shaft  1  and a plurality of smaller rollers  2 . The smaller rollers  2  are disposed around the shaft  1  and spaced from each other by a predetermined distance. The shaft  1  is generally made of a metal such as aluminum and stainless. The smaller rollers  2  are made of a material, such as rubber, that has a high surface friction, thereby preventing the paper from slipping away from the smaller rollers  2 . Nitrile rubber, urethane rubber, epichlorohydrin rubber, silicone rubber, ethylenepropylene rubber, acryl rubber, butyl rubber, etc, are largely used as the rubber material. 
     The paper-feed roller  10  made of the rubber can supply, convey and discharge the paper at the high speed using the high surface friction in an early stage of use of the paper-feed roller  10 . However, a long time use or a high-speed rotation of the paper-feed roller  10  causes a friction heat to occur on a surface of the paper-feed roller  10 , and thus the surface of the paper-feed roller  10  deteriorates. Accordingly, the surface friction is reduced such that the paper easily slips away from the paper-feed roller  10 , and there also occurs a paper jam. Especially, in a case of a photo printer printing a full image, there may occur an image distortion due to the slipping of the paper. 
     Also, if the paper-feed roller  10  has a low surface roughness, a surface abrasion is easy to occur. Therefore, a space between the smaller rollers  2  becomes wider as the paper-feed roller  10  conveys the paper, for example, approximately 20,000 sheets, for a predetermined time. 
     In order to solve the above problems of the lowered surface friction and the surface abrasion of the paper-feed roller  10 , a method has been proposed that a pipe made of stainless or carbon steel is used as the shaft, and that a ceramic coating layer is formed on a surface of the pipe. This method may overcome the shortcoming of the lowered surface friction or the surface abrasion in the conventional rubber paper-feed roller  10 , but has a difficulty in installing a gear or a gear train to the paper-feed roller  10  to transmit a rotation power to the paper-feed roller  10  due to the use of the pipe as the shaft. 
     SUMMARY OF THE INVENTION 
     The present invention has been developed in order to solve the above and other problems in the related art. Accordingly, it is an object to provide a paper-feed roller and a fabrication method capable of providing an economical effect in a fabrication cost and preventing a slippage of paper or a paper jam that is caused by a heat distortion or a abrasion occurring on a surface of a long time operated roller, by forming a plastic roller along a general shaft and forming a ceramic coating layer on a surface of the plastic roller to contact the paper. 
     Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 
     In order to achieve the above and other objects, a paper-feed roller according to an embodiment of the present invention includes a shaft and at least one roller disposed along the shaft, wherein the roller is made of plastic, and a surface of the roller to contact the paper is coated with a ceramic coating layer. 
     In an embodiment of the present invention, the shaft is made of stainless steel, and the roller is made of any one of ABC, PC, an epoxy resin, a urethane resin, a polyamide resin, a polyvinyl chloride resin, a polyethylene resin, a polyester resin, or a phenol resin. The ceramic coating layer is made of any one or any combination of Al 2 O 3 , SiO 2 , ZrO 2 , SiC, TiC, TaC, B 4 C, Cr 2 C 2 , Si 3 N 4 , BN, TiN, AlN, TiB 2 , ZrB 2 , TiO 2 , and MgF 2 . A thickness of the ceramic coating layer is equal to or below 2,000 μm. Also, the roller has corners formed at both ends thereof to prevent the ceramic coating layer from being peeled off from the surface of the roller. The ceramic coating layer has a surface friction coefficient of 1.1±10% that is obtained by a ASTM D 1894-75 method when XEROX 4200 paper is conveyed at a speed of 500 mm/min. 
     According to the present invention, a method of fabricating a paper-feed roller includes forming at least one plastic roller along a metallic shaft by a molding process and forming a ceramic coating layer of a thickness equal to or below 2,000 μm on a surface of the plastic roller. 
     The forming of the ceramic coating layer includes jetting a processing gas including a ceramic particle onto the surface of the roller from a cathode spaced-apart from the roller by 10-20 mm in conditions of a degree of vacuum ranges from 10 −2  to 10 −3  torr, a voltage equal to or below 0.1 W/cm 2 , and a low pressure plasma of the processing gas being an argon gas and an oxygen gas. 
     The ceramic particle consists of any one or any combination of Al 2 O 3 , SiO 2 , ZrO 2 , SiC, TiC, TaC, B 4 C, Cr 2 C 2 , Si 3 N 4 , BN, TiN, AlN, TiB 2 , ZrB 2 , TiO 2 , and MgF 2 . 
     The method of fabricating the paper-feed roller further includes grinding the surface of the roller to an extent of roughness that is equal to or below 2,000 μm to eliminate a foreign material from the surface of the plastic roller and achieve an easy adhesiveness of the ceramic coating layer to the surface of the plastic roller. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects and advantageous of the invention will become apparent and more readily appreciated from the following description of the preferred embodiments, taken in conjunction with the accompanying drawings of which: 
     FIG. 1 is a perspective view showing a conventional paper-feed roller; and 
     FIG. 2 is a partial section view showing a paper-feed roller in accordance with an embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described in order to explain the present invention by referring to the figures. 
     Hereinafter, a paper-feed roller and a fabrication method thereof in an image forming apparatus according to the present invention will be described in greater detail with reference to the accompanying drawing. 
     FIG. 2 shows a paper-feed roller  100  according to an embodiment of the present invention. The paper-feed roller  100  includes a shaft  1 ′ and at least one smaller roller  2 ′ disposed around the shaft  1 ′. 
     The shaft  1 ′ has a stepped portion formed at one end  3  to be engaged with a gear, and another stepped portion formed at the other end  4  to be pivotably fastened to a support frame (not shown) of a printer. In this embodiment of the present invention, the shaft  1 ′ is made of stainless steel. 
     The smaller rollers  2 ′ are disposed around the shaft  1 ′ and spaced-apart from each other by a predetermined distance. The smaller rollers  2 ′ are made of plastic, such as ABS and PC. Otherwise, an epoxy resin, a urethane resin, a polyamide resin, a polyvinyl chloride resin, a polyethylene resin, a polyester resin, or a phenol resin is used for the smaller roller  2 ′. Each small roller  2 ′ has corners  6  formed at both ends of an surface thereof to prevent a ceramic coating layer  5  from being peeled off from the surface of the smaller roller  2 ′. 
     The surface of each smaller roller  2 ′ is coated with the ceramic coating layer  5  used to contact the paper. The ceramic coating layer  5  is formed by a wet type coating method, such as an electrolysis coating method that uses water or other water solutions. However, the wet type coating method may require a high cost for fabricating the ceramic coating layer  5  on the smaller roller  2 ′ and may cause an environmental contamination. Alternatively, a dry type coating method, which does not use water or other water solutions, is used to form the ceramic coating layer  5  on the surface of the smaller roller  2 ′. There are a vacuum evaporation coating method and a sputtering method in the dry type coating method. The vacuum evaporation coating method is to evaporation-coat the surface of the smaller roller  2 ′ with a vaporized coating material. The ceramic coating layer  5  is made of any one or any combination of Al 2 O 3 , SiO 2 , ZrO 2 , SiC, TiC, TaC, B 4 C, Cr 2 C 2 , Si 3 N 4 , BN, TiN, AIN, TiB 2 , ZrB 2 , TiO 2 , and MgF 2 . The corners  6  of the smaller roller  2 ′ are not shown as being coated with the ceramic coating layer  5 . However, the corners  6  of the smaller roller  2 ′ may be coated as necessary. 
     It is possible that a thickness of the ceramic coating layer  5  is equal to or less than 2,000 μm since the overly thick ceramic coating layer  5  is easy to have a crack in the surface thereof or to be peeled off from the surface of the smaller rollers  2 ′. 
     Also, a surface friction coefficient of the ceramic coating layer  5  is 1.1±10% that is obtained by a ASTM D 1894-75 method when XEROX 4200 paper is conveyed at a speed of 500 mm/min. The surface friction coefficient is increased or decreased by adjusting a volume of a ceramic particle included in a processing gas that is used during the vacuum evaporation coating or sputtering process. 
     A fabrication method of the paper-feed roller according to another embodiment of the present invention will be described. 
     The shaft  1 ′ made of the stainless steel is prepared, and the stepped portions are formed at both ends  3  and  4  of the shaft  1 ′ by a mechanical process. One of the stepped portions is to be engaged with the gear, and the other one of the stepped portions is to be pivotably fastened to the support frame (not shown) of the printer to support the shaft  1 ′ with respect to the support frame. 
     After that, as shown in FIG. 2, the smaller rollers  2 ′ are made of plastic, such as the ABS and PC, and are directly formed on an outer surface of the shaft  1 ′ by an injection molding process or a molding process. The smaller rollers  2 ′ are spaced from each other by the predetermined distance. 
     After the smaller rollers  2 ′ are formed along the shaft  1 ′, a residual stress or a foreign material, such as H 2 O, CO 2 , and SO 2 , are eliminated from the surface of the smaller rollers  2 ′. Next, the smaller rollers  2 ′ are ground to have a surface roughness of an average equal to or less than 2,000 μm. Due to the surface roughness of the smaller rollers  2 ′, the ceramic coating layer  5  is easily evaporation-coated on the smaller roller  2 ′. The average surface roughness of the smaller rollers  2 ′ is approximately 2,000 μm in order not to ruin an appearance of the smaller rollers  2 ′ even with the ceramic coating layer  5  evaporation-coated thereon. 
     After the smaller rollers  2 ′ are ground, the vacuum evaporation coating or sputtering process is performed on the shaft  1  in a processing chamber. 
     In the processing chamber, the surface of the smaller rollers  2 ′ is coated with the ceramic coating layer  5  in a manner that the processing gas including the ceramic particle is jetted onto the smaller rollers  2 ′ from a cathode being distanced from the smaller rollers  2 ′ by 10-20 mm under conditions that a degree of vacuum ranges from 10 −2  to 10 −3  torr, a voltage is equal to or less than 0.1 W/cm 2  to prevent a heat distortion or a damage on the smaller rollers  2 ′, and a low pressure plasma of the processing gas consists of an argon gas or an oxygen gas. 
     At this point, the ceramic particle included in the processing gas uses any one or any combination of Al 2 O 3 , SiO 2 , ZrO 2 , SiC, TiC, TaC, B 4 C, Cr 2 C 2 , Si 3 N 4 , BN, TiN, AIN, TiB 2 , ZrB 2 , TiO 2 , and MgF 2  for a dimorphic characteristic and a physical and chemical endurance of the ceramic coating layer  5 . The thickness of the ceramic coating layer  5  is adjusted to be equal to or less than 2,000 μm. 
     Then, the surface of the smaller rollers  2 ′ being coated with the ceramic coating layer  5  is sealed. That is, the ceramic coating layer  5  is coated with an organic substance, such as epoxy and wax, such that the epoxy and wax fills up an air cell in the ceramic coating layer  5 . The sealing of the ceramic coating layer  5  is to prevent a brittle failure of the ceramic coating layer  5  in the following process. 
     After completing the sealing, a plate surface grinding process is finally performed in order to increase a degree of flatness of the ceramic coating layer  5 . 
     The present invention will now be described in detail with reference to the following Example. However, it is understood that the invention is not limited thereto. 
     EXAMPLE 
     The shaft  1  was made of the stainless steel, and the smaller rollers  2 ′ were made of general plastic, such as the ABS and PC. A combination of Al 2 O 3  and SiO 2  was used as a ceramic coating material of the ceramic coating layer  5 . The surface of the smaller rollers  2 ′ was distanced from the cathode by 10-20 mm in the processing chamber under the conditions that the degree of vacuum ranged from 10 −2  to 10 −3  torr, the voltage was equal to or less than 0.1 W/cm 2 , and a low pressure plasma of the processing gas was the argon gas and the oxygen gas. 
     The surface friction coefficient of the ceramic coating layer  5  was 1.1±10% that was obtained by the ASTM D 1894-75 method when the XEROX 4200 paper was conveyed at the speed of 500 mm/min. The surface friction coefficient was kept constant when 100,000 sheets of the paper were used and conveyed through the smaller rollers  2 ′ of the shaft  1 ′. 
     As described above, the paper-feed roller and the fabrication method thereof according to the present invention is capable of providing an economical effect in a fabrication cost and preventing a slipping of paper or a paper jam that is caused by a heat distortion and an abrasion occurring on a surface of a long time operated roller, by forming the smaller rollers along the general shaft and by coating the surface of the smaller rollers to contact with the paper. 
     Although a few preferred embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and sprit of the invention, the scope of which is defined in the claims and their equivalents.