Image forming apparatus capable of forming a duplex image on one sheet

Abstract

An image forming apparatus, including an image forming part which forms an image on a printing medium, a main feeding part which accommodates the printing medium and supplies the printing medium to the image forming part, and a reversing part which transfers the printing medium, on which an image is formed on a first surface thereof in the image forming part, to the main feeding part, wherein the main feeding part includes a feeding roller part which re-feeds the printing medium, having been transferred through the reversing part, to the image forming part.

What is claimed is: 
     
         1 . An image forming apparatus, comprising:
 an image forming part which forms an image on a printing medium;   a main feeding part which accommodates the printing medium and supplies the printing medium to the image forming part; and   a reversing part which transfers the printing medium, on which an image is formed on a first surface thereof in the image forming part, to the main feeding part, wherein the main feeding part includes a feeding roller part which re-feeds the printing medium, having been transferred through the reversing part, to the image forming part.   
     
     
         2 . The image forming apparatus according to  claim 1 , further comprising:
 a casing which accommodates the image forming part; and   a sub-feeding part outside of the casing and which supplies the printing medium to an interior of the casing, wherein the feeding roller part transfers the printing medium supplied by the sub-feeding part to the image forming part.   
     
     
         3 . The image forming apparatus according to  claim 2 , wherein the main feeding part comprises:
 a main feeding part main body which accommodates the feeding roller part and which is detachably mounted to the casing; and   a main feeding cassette part which is spaced from the main feeding part main body and which stores the printing medium.   
     
     
         4 . The image forming apparatus according to  claim 3 , wherein the main feeding cassette part comprises:
 a knock-up plate in which the printing medium is stored;   a main pick-up roller which picks up the printing medium in the knock-up plate; and   a registration roller which aligns a leading edge of the printing medium picked up in the main pick-up roller and which transfers the printing medium to the image forming part.   
     
     
         5 . The image forming apparatus according to  claim 4 , wherein the feeding roller part comprises:
 a sub pick-up roller which picks up the printing medium in the sub-feeding part; and   a feeding roller which transfers the printing medium transferred to the reversing part and the printing medium picked up by the sub pick-up roller to the image forming part.   
     
     
         6 . The image forming apparatus according to  claim 5 , wherein the reversing part comprises:
 a reversing path which is provided in the casing and on which the printing medium is transferred; and   a reversing roller which is provided on the reversing path and which transfers the printing medium, wherein, a first guide member which guides the printing medium to the feeding roller is provided in one end part of the reversing path.   
     
     
         7 . The image forming apparatus according to  claim 6 , wherein the feeding roller part comprises a second guide member which is provided on one side of the feeding roller and which guides the printing medium, the printing medium having been guided through the first guide member to the feeding roller. 
     
     
         8 . The image forming apparatus according to  claim 5 , wherein the feeding roller feeds the printing medium, the printing medium having been transferred to the reversing path and the printing medium having been picked up in the sub pick-up roller to the registration roller. 
     
     
         9 . An image forming apparatus, comprising:
 an image forming unit to form an image on a printing medium;   a main feeding unit to supply the printing medium to the image forming unit;   a reversing unit to transfer the printing medium, on which an image is formed on a first surface thereof in the image forming unit, to the main feeding unit; and   a feeding roller installed in the main feeding unit to re-feed the printing medium, having been transferred through the reversing unit, to the image forming unit.   
     
     
         10 . The image forming apparatus according to  claim 1 , further comprising:
 a casing to accommodate the image forming unit; and   a sub-feeding unit, outside of the casing, to supply the printing medium to an interior of the casing, wherein the feeding roller transfers the printing medium supplied by the sub-feeding unit to the image forming unit.   
     
     
         11 . The image forming apparatus according to  claim 10 , wherein the main feeding unit comprises:
 a main body to accommodate the feeding roller and to detachably mount to the casing; and   a main feeding cassette, spaced from the main body, to store the printing medium.   
     
     
         12 . The image forming apparatus according to  claim 11 , wherein the main feeding cassette comprises:
 a knock-up plate to store the printing medium;   a pick-up roller to pick up the printing medium from the knock-up plate; and   a registration roller to align a leading edge of the picked up printing medium and to transfer the printing medium to the image forming unit.   
     
     
         13 . The image forming apparatus according to  claim 12 , wherein the feeding roller comprises:
 a sub pick-up roller to pick up the printing medium from the sub-feeding unit; and   a feeding roller to transfer the printing medium, having been transferred to the reversing unit, and the printing medium, having been picked up by the sub pick-up roller, to the image forming unit.   
     
     
         14 . The image forming apparatus according to  claim 13 , wherein the reversing unit comprises:
 a reversing path, provided in the casing, on which the printing medium is transferred;   a reversing roller, provided on the reversing path, to transfer the printing medium; and   a first guide member to guide the printing medium to the feeding roller, the first guide member being provided in one end part of the reversing path.   
     
     
         15 . The image forming apparatus according to  claim 14 , wherein the feeding roller comprises a second guide member, provided on one side of the feeding roller, to guide the printing medium, the printing medium having been guided through the first guide member to the feeding roller. 
     
     
         16 . The image forming apparatus according to  claim 13 , wherein the feeding roller feeds the printing medium, the printing medium having been transferred to the reversing path and the printing medium having been picked up in the sub pick-up roller to the registration roller.