GB516748A - Improvements in photographic enlarging apparatus - Google Patents

Abstract

516,748. Photographic projection printers. McKERROW, C. N. July 8, 1938, No. 20226. [Class 98 (i)] In an enlarging apparatus of the kind in which the projection apparatus is vertically adjustable relatively to a fixed printing table, the projection lens and illuminant remain at a constant distance apart throughout the enlarging range, and are moved jointly relatively to the condenser and negative carrier, in order to effect automatic focusing adjustment and to maintain the illumination of the negative uniform, by the single operation of setting the projection apparatus for a given degree of enlargement. Provision is made also for (1) disconnecting the automatic focusing mechanism to permit manual focusing (2) adapting the automatic focusing mechanism to the focal length of the projection lens used, and (3) varying the intensity of the printing light by including at will in its circuit a ruby inspection lamp. As shown, the apparatus comprises a stationary printing table a and a graduated pillar b mounted on the table and having guides for a counterweighted slipper e, Fig. 5, carrying a bracket e<1> supporting the housing g for the lamp h, condenser j, negative holder k, and the lens l. The lens-holder and the lamp are carried by a slide q to which is secured a slotted plate u, Fig. 3, the slot being formed with gaps u<4> into either of which a stoppin u<5> mounted on a spring-arm u' pivoted to the slide may be sprung. The slide is adjusted by a short arm m<2> abutting against the pin and secured to a focusing arm m having a stud engaging a slot in a quadrant scale n for manual focusing. For automatic focusing, the arm is provided with rollers s, s', the latter of which is carried by a spring s<2> mounted on the arm, adapted to be engaged over a cam-rail o, and is held in place by a rigid tongue t secured to the friction-damper m<1> of the arm by a wing-nut and engageable with a bracket m<3> on the arm. The lamp may be adjustably secured in a ring h<2> carried by a vertically adjustable plate h<3> secured to the slide. In a modification, the lamp is carried by a vertical rod slidable through the top of the housing g, and secured to the slide q. The lamp h may be disposed in circuit with ruby coloured resistance lamp v controlled by a three-way switch so that the ruby lamp may be switched on either with the lamp h to vary the intensity of the printing light, or independently of the lamp h to facilitate setting of the apparatus. Specification 461,574 is referred to.