Abstract:
An optical system for a duplicator machine comprising a table on which a pair of mirrors are mounted, the pair of mirrors jointly reflecting light from a document 180° to a photosensitive surface. The table is supported for easy adjustment on a pair of eccentric cams mounted adjacent the ends thereof, the table being coupled to the cams by means of rotatable adjusting screws for establishing an initial level of the table.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to an optical system for a duplicator machine, and more particularly to an optical system of a construction which allows easy adjustment and replacement as compared with existing counterparts. 
     The existing optical system for duplicator machines, for example, lenses and mirrors, generally undergo positional deviations due to vibrations occurring as a result of operation of the duplicator machine or imposed from outside, giving rise to various defects such as blurring of the original image on the copying surface or the like. These defects can be avoided by periodic adjustment of the optical system, but such adjustments involve troublesome efforts including positional and angular adjustments of lenses, and reflecting mirrors independently as well as in relation to other component parts of the optical system. 
     OBJECT OF THE INVENTION 
     The present invention aims at removing the aforementioned defects and has as its object the provision of an optical system particularly suitable for use in duplicator machines and having a simplified construction particularly designed to facilitate the positional adjustments to a material degree and at the same time to allow easy maintenance and replacement thereof. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagramatic view showing general construction of a duplicator machine employing an optical system according to the present invention, and; 
     FIG. 2 is a perspective view showing the optical system of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of the present invention will now be described more particularly with reference to the accompanying drawings. 
     Referring to FIG. 1 which shows a general construction of a duplicator machine employing the optical system according to the present invention, there is designated at 1 a document drum and at 2 a photosensitive drum. An original document 4 which has been inserted through a document inlet 3 is transferred through an exposure position 5 by means of the document drum 1. An image of the original document 4 is formed as an electrostatic latent image on the photosensitive drum 2 by means of an optical system which will be described in greater detail hereinafter. Thereafter, the original 4 is discharged onto a document receptacle tray 7. The electrostatic latent image formed on the photosensitive drum 2 is visualized by means of a developing device 8 which is mounted on the circumference of the photosensitive drum 2 and the developed image is transferred at a transfer position onto a paper sheet 10 which is fed from a paper feeding device 9, by means of a transfer corona device 11. The paper sheet 10 which has been transferred with a visible image is directed to a fixing device 13 by the action of a chain 12, the fixing device operating to make the toner image permanent before the copy is discharged into the receptacle tray 14. Toner residue on the photosensitive drum 2 is removed by a cleaning station device 15. 
     In connection with a duplicator machine of the construction as mentioned hereinabove, the optical system 5 of the invention will be discussed hereafter. 
     The optical system 6 comprises a horizontally disposed table or platform 17 on which are mounted a lens 18, and reflecting mirrors 19a and 19b. Adjusting screws 20a, 20b, 20c and 20d are provided to form an independent optical unit. The lens 18 is fixedly mounted substantially at the center of the table 17 while the reflecting mirrors 19a and 19b are fixedly mounted at opposite ends thereof at approximately a 45° angle in facing relation with the document drum 1 and photosensitive drum 2, respectively. Thus, the light passage from the document drum 1 to the photosensitive drum 2 is constituted only by horizontal and vertical elements, so that the adjustment of focus may be attained suitably by moving the table 17 in the vertical direction. Elongated slots 21a and 21b are formed in the table 17 to permit light to pass between the document drum and the reflecting mirror 19a on the one hand between the photosensitive drum 2 and the reflecting mirror 19b on the other hand. 
     The aforementioned optical system 6 is supported on support members 22a and 22b which are suspended on the duplicator machine body and extended in the axial direction of the document drum 1 and photosensitive drum 2 between side walls 23a and 23b. The support members 22a and 22b are in the form of eccentric cams, so that the distances A and B of the vertical light passages between the uppermost levels of the document drum 1 and the support member 22b may be varied and adjusted by rotating the support members 22a and 22b, respectively. After adjustment, the support members 22a and 22b are fixed in position by suitable fixing means, such as nuts or the like. 
     In the manner just mentioned, the optical system 6 is mounted on the support members 22a and 22b. The bottom face of the table 17 of the optical system 6 is formed with two transversely extending semi-cylindrical grooves 24a and 24b for receiving the support members 22a and 22b. Therefore, the level of the table 17 may be adjusted by means of the adjusting screws 20a, 20b, 20c and 20d which are fixed in position by suitable fixing means such as double nuts or the like after adjustment of the table 17. 
     After mounting the optical system 6 on the support members 22a and 22b, the adjusting screws 20a, 20b, 20c, and 20d are set to satisfy the following equations: 
     
         C = (1 + 1/M)f - (A + B) and 
    
     
         D = (1 + 1/M)f - (A + F) 
    
     wherein C is the vertical distance between the top level of the support member 22a in the form of an eccentric cam and the center of the reflecting mirror 19a, D is the vertical distance between the top level of the support member 22b in the form of an eccentric cam and the center of the reflecting mirror 22b, M represents the magnification of the lens, f represents the focal length of the lens, E represents the distance between the centers of the reflecting mirror 10a and the lens 19, and F represents the distance between the centers of the reflecting mirror 10b and the lens 18. 
     The setting of the adjusting screws 20a, 20b, 20c, and 20d may alternatively be effected visually by forming an image of the original on the photosensitive drum 2. 
     After setting the optical system 6 in position, both the optical system 6 and the support members 22a and 22b are fixed immovable with respect to each other by suitable fixing means such as a band or a clamping device (not shown). 
     As described hereinbefore, the optical system for a duplicator machine according to the present invention comprises on the table 17, a first reflecting mirror 19a for reflecting a light ray emitted in a normal direction from the surface of an original on the document drum 1 in a direction perpendicular to a line normal to the surface of the original, a lens 18 disposed in the passage of the reflected light ray, and a second reflecting mirror 19b for reflecting the received beam 90° and projecting the light rays onto a photosensitive drum 22a, the table 17 being coupled to support members 22a and 22b, by means of a plural number of adjusting screws 20a, 20b, 20c, and 20d to allow adjustment of the level of the table. The support members are supported from the machine frame so that the table 17 may be adjusted in the vertical direction with ease by rotation of the support members which are in the form of eccentric cams spaning the width of the table parallel to the plane of the reflecting mirrors. The optical system thus has the advantage of allowing easy maintenance and replacement.