Patent Publication Number: US-5251892-A

Title: Method of and apparatus for ejecting paper in a printing system

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a method of and apparatus for ejecting paper in printers, copiers and the like. 
     A conventional paper ejecting apparatus for a video color printer is illustrated in FIG. 1. The printer is a video color printer that is commercially available as Model No. VY-Pl manufactured by Hitachi Co., Japan. In the Hitachi apparatus, a printed sheet of paper 11 is transferred between upper and lower panels 1 and 2 by feed rollers 3 and 4, rotating in contact with each other. Thereafter, paper 11 is pushed forward by push arms 5 and 6 between panels 1 and 2, and then is outwardly ejected by exhaust rollers 9 and 10. Push arms 5 and 6 provided with sector gears 51 and 61, respectively, are installed to pivot on axes 52 and 62, respectively, so as to allow sector gears 51 and 61 to rotate while meshed. Also, one push arm 5 is provided with an interlocking pin 53 to be drawn by a spring 7, so that push arms 5 and 6 are operated by the pulling and pushing of interlocking pin 53 by means of a slide member 8 moving in the directions of arrows A. That is, when slide member 8 pushes interlocking pin 53, the gap between push arms 5 and 6 is widened, and as paper 11 is supplied between panels 1 and 2, slide member 8 retreats. According to this operation, the gap between push arms 5 and 6 is narrowed by the restoring strength of spring 7, thus forcing paper 11 out. 
     In the conventional apparatus thus described the push arms 5 and 6 function as tongs, and work very swiftly due to the resilience of the spring. The apparatus, however, has problems in that the paper, which is thin and flexible, is easily crumpled, jammed, or both, in the interval between the panel and the push arm, thus creating trouble in ejecting the paper. Further, since the traveling distance of the paper pushed by the push arms 5 and 6 is not long enough to completely eject the paper, the exhaust rollers 9 and 10 must be installed to completely eject the paper. As a result, the apparatus is complicated in structure, expensive, and generates considerable noise. 
     SUMMARY OF THE INVENTION 
     Therefore, it is the object of the present invention to provide a paper ejecting apparatus in a printing system, wherein a simplified process and structure is employed to smoothly eject a printed sheet of paper without the sheet being damaged or jammed in the printer. 
     To achieve the above and other objects of the present invention, there is provided a paper ejecting method and apparatus in a system such as a video color printer which includes upper and lower panels spaced apart from each other and feed rollers for transferring a printed sheet of paper from a recording side into the space between upper and lower panels, thereby outwardly ejecting the paper transferred between the upper and lower panels. The apparatus is typically composed of: 
     long guide channels formed in the lower panel and extending in the ejecting direction of the paper; 
     a pusher having portions inserted into the guide channels to slide along the guide channels; 
     a rack gear member connected to and moved together with the pusher; 
     a guide support member for guiding the movement of the rack gear member; and 
     a driving mechanism for driving the rack gear member with a rotated pinion while being engaged with the rack gear member and driven by a driving source, 
     whereby the printed sheet of paper is ejected by the pusher after being placed in front of the pusher. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects and advantages of the present invention will be apparent from the detailed description below with reference to the accompanying drawings, in which: 
     FIG. 1 is a perspective view of a paper ejecting apparatus in a conventional video color printer; 
     FIG. 2 is a perspective view of a paper ejecting apparatus in a video color printer according to the present invention; and 
     FIG. 3 is a sectional view showing the detailed structure of a driving unit of the paper ejecting apparatus in the video color printer of FIG. 2 according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION 
     Referring to FIG. 2, a paper ejecting apparatus according to the present invention is explained as follows as embodied in a video color printer. 
     Upper and lower panels 1 and 2 spaced apart from each other are formed as one body by an extension 12, having an inlet 13 for feeding paper from one side and an outlet 14 in the front for outputting the paper. A pair of feed rollers 3 and 4 installed on inlet 13 is used to transfer a sheet of paper 11 between panels 1 and 2; preferably the paper has been exposed to a printing process (printed) by a recorder of the printer (not shown). A pair of parallel guide channels 15 and 16 extending toward outlet 14 are formed in lower panel 2. 
     A pusher 17 is installed such that ends 18 and 19 are together inserted into guide channels 15 and 16, respectively, thereby allowing movement along the guide channels 15 and 16. Pusher 17 is first positioned at the back ends of guide channels 15 and 16 by a rack gear member and an associated driving unit which will be described later. After paper 11 is transferred by feed rollers 3 and 4, pusher 17 is moved forward toward outlet 14 so that paper 11 is completely ejected through the outlet 14. 
     A rack gear member 20 is connected to the reverse side of pusher 17. Rack gear member 20 is supported by a guide support member 21 formed on lower panel 2, to be moved along guide support member 21. Rack gear member 20 is formed of a flexible material, and as seen in the drawing, guide support member 21 is arc-shaped, so that together members 20 and 21 occupy only a small portion of the surface space between panels 1 and 2. 
     A pinion 22 protrudes through one part of guide support member 21 to be engaged with rack gear member 20 within guide support member 21. 
     As illustrated in FIG. 3, a driving unit has a driving source that includes motor 23 for driving rack gear member 20 along with pinion 22. A driving gear 24 on the shaft of motor 23 is engaged with transmission gear 25. A pair of bevel gears 27 and 28, which are engaged with each other, are installed on a transmission shaft 26 of transmission gear 25 and a driven shaft 29, respectively. The transmission shaft 26 is supported by a separate bracket 30 installed on lower panel 2, and driven shaft 29 is directly supported by lower panel 2. Together with bevel gear 28 pinion 22 is installed on driven shaft 29. In order to prevent overload operation, both a friction disc 31, which is provided with felt 32 in contact with one side of bevel gear 27, and also a spring 33, which is used to bias bevel gear 27 toward friction disc 31, are added onto transmission shaft 26. Bevel gear 27 can be slidably rotated around transmission shaft 26, and friction disc 30 is secured to transmission shaft 26. Motor 23 is capable of rotating in both forward and reverse directions and is capable of being timely controlled in accordance with a control circuit (not shown). 
     The operation of the paper ejecting apparatus according to the present invention thus constructed is described below. 
     The apparatus shown in FIG. 2 is a part of a video color printer, e.g., of a thermal transfer printing system, in which the recorder of the printer is positioned toward inlet 13 of panels 1 and 2. In accordance with the conventional method, a picture is recorded on paper 11 by a thermal transfer head in the recorder (not shown). After completing the printing process, a printed sheet of paper 11 is transferred toward inlet 13 of panels 1 and 2, and is successively input between panels 1 and 2 by feed rollers 3 and 4 installed at inlet 13. At this time, since pusher 17 is positioned at the back ends of guide channels 15 and 16, paper 11 is placed in front of pusher 17. 
     After placing the sheet of paper 11 in front of pusher 17, motor 23 begins operating. When motor 23 is operated, transmission shaft 26 is rotated by the rotations of gears 24 and 25, and driven shaft 29 is rotated by the rotations of bevel gears 27 and 28. Upon the rotation of driven shaft 29, pinion 22 is rotated to set rack gear member 20 in motion. By this operation of rack gear member 20, and while sliding toward outlet 14 along guide channels 15 and 16, pusher 17 forces paper 11 out of outlet 14. Accordingly, paper 11 is ejected through outlet 14 by pusher 17. 
     Overload due to various operation conditions restrains driven shaft 29, and when the restraining force is greater than the friction which is generated by the pressing of spring 33, between bevel gear 27 and felt 32 of friction disc 31, then bevel gears 27 and 28, driven shaft 29, and pinion 22 will not rotate due to slippage between bevel gear 27 and felt 32. This phenomenon appears also as motor 23 continues to rotate when pusher 17 reaches the far end of guide channels 15 and 16; thus, accurate timing is not required for controlling motor 23. 
     After ejecting paper 11, motor 23 is controlled to be rotated in the reverse direction, and pusher 17 retreats to its initial position. 
     In the above-described paper ejecting apparatus according to the present invention, since the rotation movement is converted into linear motion to push out the paper, the ejection of the paper is smooth. Therefore, the mechanical noise is low, and the paper is not crumpled or jammed between the pusher and panel, thus the successful ejecting operation of the paper is ensured. In addition, in the apparatus of the present invention, the paper is ejected by the sliding movement of the pusher, so that the traveling distance of the pusher can be set to an adequate length, which in turn enables troublefree ejection of the paper solely by the movement of the pusher without requiring the conventional ejecting rollers 9 and 10 shown in FIG. 1. As a result, the apparatus of the present invention is of good quality and inexpensive as compared with the conventional apparatus. 
     While a preferred embodiment of the invention has been described using specific terms in particular application within a video color printer, such description is for illustrative purposes only, and it is to be understood that changes and variations may be made without departing form the spirit or scope of the following claims.