Patent GB-446676-A (GB)
Title: Improvements in or relating to photographic printing apparatus
IPC: G01J1/42
Filed: 1934-11-02
Abstract: 446,676. Photographic printing - apparatus. KODAK, Ltd., Kingsway, London.- (Assignees of Tuttle, C. M., and Young, D'A. A. ; Kodak Park, Rochester, New York, U.S.A.) Nov. 2, 1934, No. 31471. Convention date, Nov. 4, 1933. [Classes 98 (i) and 98 (ii)] In photographic printing- apparatus of the kind in which the exposure during the printing period is automatically determined in accordance with the density of the negative as by utilizing a light radiation sensitive element which measures the light transmission through the negative the exposure is also automatically determined in accordance with a setting as determined by the size of the negative. As shown, a contactprinting apparatus comprises a printing panel 10 over which slide masking strips 12, 13 and on which the negative is held by a clamp 14. The printing paper is held by a spring finger 15 and is pressed on the negative during printing by a platen 16. Light from the printing lamp 19, to which current is supplied through a fixed resistance 20, is reflected after passage through a non-actinic filter 23 by a mirror 24 on to the panel 10. Photoelectric cells 25 are connected to a coil 28 controlling a movable contact 29 to adjust the effective value of a resistance 30. The strip 13 has a finger 31 sliding over a bar 32 and also over contacts 33 connected to the resistance 34 so that movement of the strip 13 controls the effective value of the resistance 34. The clamp 14 is mounted in a slot in a bar 35 controlled by a crank 37 and a rod 36 upwardly biassed by the spring 38 acting on a crank 39 on a rod 40 connected to a control lever 41. Secured to the lever 41 is a rod 43 having an arm 44 provided with a contact bar 44 co-operating with contacts 46, 47 and 48, and also having a collar 54 engaging a forked lever 55 on a shaft 56 carrying a crank 57 having a pin 58 engaging in a slot in a block 59 controlling by means of the presser bar 60 the engagement of the contact 29 with the resistance 30. The motor 18 is connected by means of the clutch 62 to a shaft 61 carrying a cam 63 co-operating with the lever 65 to control through the link 66 and arm 67 the movement of the platen 16 and also carrying a cam 69 co-operating with a vacuum-switch 70 to close or open a circuit placing the resistance 30 in parallel with the resistance 20. A lever 74 carrying a hook 75 and button 76 holds the clutch 62 out of engagement until the button 76 is depressed, whereupon the clutch performs a single revolution and the hook 75 re-engages a notch in the clutch. When the platen 16 is lowered, the lever 65 rotates a member 78 to move the filter 23 out of the light beam. The masks 12, 13 are adjusted to the negative size, the control lever 41 moved to the right to raise the clamp 14 and to bridge the contacts 46, 47 and include the resistance 34 in the printing lamp circuit. The lever 41 is then released, the button 76 depressed, whereupon the platen 16 is lowered, the filter 23 moved from the light-path, and the switch 70 closed for a period determined by the cam 69. The switch 70 then opens, the platen 16 is raised, and the filter 23 is returned to operative position. When vigorous paper is used the lever 41 is moved to the extreme right to connect the resistance 79 in series with the resistance 34 and adjust the lamp 19 for brighter illumination. For printing very dense negatives a 50 per cent filter may be moved by hand into the light-beam during the exposure period. Specification 405,033 is referred to.