Patent Publication Number: US-5294957-A

Title: Drive means of an electro-photography process unit

Description:
TECHNICAL BACKGROUND 
     The present invention relates to a drive means of an electro-photography process unit. 
     Referring to FIG. 1 for illustrating a conventional electro-photography process unit, the surface of a photo-sensitive drum 28 is uniformly charged with a constant voltage by an electric charger 25 and then exposed to the light of a lamp 24 reflected from an original document placed on a platen glass 21, so that an electrostatic latent image is formed on the photo-sensitive drum 28 corresponding to the image of the document. The light source may be a laser scanning unit, light emitting diode, etc. Thereafter, as the photo-sensitive drum 28 is rotated, the toner of a developer 27 is attracted to the surface of the photo-sensitive drum 28 so as to develop the latent image transferred by a transfer means 32 to a sheet of paper supplied by a supply roll 20. 
     The paper adhering to the photo-sensitive drum 28 by the electrostatic force is separated by a separator 33 therefrom. Then the paper is conveyed by a conveyor belt 30 to a fixing means 40, where the paper is heated and pressed between a heat roll 34 and pressure roll 35 to fix the toner, conveyed to a discharging tray 39. 
     The residual toner on the photo-sensitive drum 28 is removed by a cleaning blade 29 and the latent image is canceled by the light supplied from a pre-erase lamp array 37. 
     FIG. 2 reveals the photo-sensitive drum 28 and magnet roll 27b which are driven by drive means as shown in FIGS. 3A and 3B. A motor has a shaft provided with a gear 22 and pulley 22a. The gear 22 is to transmit the power of the motor via a train of gears 41, 42 and 43 to a drum gear 28a. Meanwhile, the power of the motor is also transmitted via a pulley 22a, timing belt 45, pulley 44, idle gear 43a, magnet roll drive gear 46 to the magnet roll 27. 
     Such conventional drive means is very complicated, requiring a large installing space and many parts, thus increasing the production cost. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to simplify the structure of the part of the drive means of an electrophotography process unit for driving the magnet roll of the developer, thereby decreasing the volume as well as the production cost of the electrophotography process unit. 
     According to the present invention, there is provided a drive means of an electro-photography process unit comprising a first idle gear means consisting of two gears coaxially arranged with a space, for transmitting the power of a motor to a drum drive gear mounted on a shaft of a photo-sensitive drum and to a second idle gear means with a different pitch for transmitting the power to a developer, the developer being arranged on one side of the drum, a magnet roll provided in the developer for transferring toner to the drum, a first speedup gear with a different pitch engaged with the second idle gear means for driving the magnet roll, and a second speedup gear with a different pitch engaged with the first speedup gear and with a gear of the magnet roll. 
     The present invention will now be described more specifically with reference to the drawings attached only by way of example. 
    
    
     BRIEF DESCRIPTION OF ATTACHED DRAWINGS 
     FIG. 1 is a schematic diagram for illustrating the structure of a conventional electro-photography process unit; 
     FIG. 2 is an enlarged side view of a part of FIG. 1; 
     FIG. 3A is a schematic view of a conventional drive means; 
     FIG. 3B is a side view of FIG. 3A; 
     FIG. 4A is a view similar to FIG. 3A but according to the present invention; and 
     FIG. 4B is a side view of FIG. 4A. 
    
    
     DETAILED DESCRIPTION OF A CERTAIN PREFERRED EMBODIMENT 
     Referring to FIGS. 4A and 4B, a first idle gear means 50 consists of two gears 50a and 50b of different sizes coaxially arranged with a space. The smaller gear 50a is engaged with a drum drive gear 28a mounted on the rotational shaft of the photo-sensitive drum 28. The larger gear 50b is to transmit the power of a motor to the developer 27. A second idle gear means 51 consists of a smaller gear 51a and larger gear 51b. The smaller gear 51a is engaged with the larger gear 50b of the first idle gear means 50, and the larger gear 51b with a first speedup gear 52, which in turn is engaged with a second speedup gear 53 of a different pitch engaged with a magnet roll gear 27a mounted on the shaft of the magnet roll. 
     In operation, the photo-sensitive drum 28 charged by the electric charger 25 is rotated by means of the drum drive gear 28a. Namely the rotational motion of the motor is transmitted via the idle gears 61, 60 to the idle gears 50a, 50b, so that the drum drive gear 28a engaged with the idle gear 50a is rotated. Meanwhile the rotational motion of the idle gears 50a, 50b is transmitted via the idle gear means 51 to the developer 27. 
     Thus the first speedup gear 52 drives the second speedup gear 53 provided in the developer 27. The second speedup gear 53 in turn drives the magnet roll gear 27a of the magnet roll.