GB915726A - Drive system for photographic whiteprint machines - Google Patents

Abstract

915,726. Photo copying machines. GENERAL ANILINE & FILM CORPORATION. Sept. 30, 1960 [Oct. 1, 1959], No. 33663/60. Class 98 (2). [Also in Groups XVI and XXIV] In photo copying apparatus a continuous length of light-sensitive material is passed through an exposing area and then through a printing area, by means of two endless belt conveyer systems, one system serving each area; means are provided for conveying power from a motor to a drive roller for the first of said systems, and from that drive roller to the drive roller of the second of said systems, this latter means including a unidirectional coupling element ; ancillary means are also provided for conveying power from said first to said second drive roller by-passing said unidirectional coupling, the effectiveness of the ancillary means being adjustable. In the form shown, the sheet of sensitive material 27 is fed in from a supply roll 28 and passes, together with an original, between endless belts 10, 17 round a cylinder 8 and light source 9 where the exposure takes place. The sheets then pass between belts 10 and 84 where they are separated by suction devices 82, 89. The original passes out on to tray 87, while the sensitive sheet passes to the developer section, where it is held by belt 33 against a vapour developing tank 30, finally being led either out of the apparatus through an exit opening, or on to a receiving tray 45. The endless belts 10, 33 form the two main conveyer systems, serving the " exposure " and " development " stations, respectively. The rollers 11 and 35 form the drive rollers of these two sections, respectively. The power source is a motor, connected directly by a chain drive 48 to a sprocket 35<SP>1</SP> fixed to roller 35. The sprocket 35<SP>1</SP> is of double construction, having a second sprocket section 59, which drives a chain 53 passing over further sprockets 11<SP>1</SP> and 54. Sprocket 11<SP>1</SP> drives the roller 11, which is the drive roller for the belt 10. Thus the motor directly drives roller 35 and thence roller 11, themselves the drive rollers for the two main conveyer belts. The sprocket 11<SP>1</SP> is not directly keyed to the main shaft 62 of roller 11, but drives it via a unidirectional ball-clutch 63, so that roller 11 can turn at a higher speed than that provided by chain 53. The sprocket 54, which is also driven by chain 53, rides freely on a stud 68 fixed to the supporting wall 69. Another sprocket 74 also rides freely on stud 68, and is connected by a chain 56 to a sprocket 80 keyed to the shaft 62 of roller 11. This is the ancillary drive means referred to above. A friction clutch 67 is mounted on stud 68, and can be engaged against sprocket 54 to an adjustable degree by means of a spring 76 whose compression is controlled by a knob 78. The other side of sprocket 54 has a face-plate 72 which can engage frictionally against another face-plate 73 attached to sprocket 74. Thus when friction clutch 67 is completely disengaged, sprockets 54 and 74 turn freely and loosely on stud 68. As knob 78 is turned, to engage the clutch, sprockets 54 and 74 engage frictionally, and the drive from sprocket 35<SP>1</SP> via chain 53 is transmitted not only to sprocket 11<SP>1</SP> (and hence to roller 11) but also, via sprockets 74 and 80, to roller 11 directly, by-passing sprocket 11<SP>1</SP> and the ball-clutch 63. The drive operation is as follows. If a length of sensitized material 57 is travelling through the machine, and a greater pull is exerted on the material by the " development " belt system (driven by roller 35), this would tend to tear the material. But since the ball-clutch 63 allows the roller at the feed-in position (roller 11) to rotate at a higher speed than the drive, this pull or tension in the material is eliminated. However, this alone would not be adequate unless the material itself had a greater tensile strength than sensitized paper usually possesses. Assistance is provided, therefore, by the ancillary drive, which acts as a torque-assist mechanism. This transmits part of the drive directly to roller 11, bypassing clutch 63, thus assisting the paper feed. The degree of assistance can be set by adjusting knob 78 controlling the friction clutch 67, and this adjustment, once made, should remain reasonably constant for any particular type of paper.