GB632781A - Photographic enlarging apparatus with automatic focusing provision - Google Patents

Abstract

632,781. Photographic enlargers. PASQUET, R. L. Dec. 8, 1945, No. 33235. Convention date, March 17. [Class 98 (i)] In a photographic enlarger of the kind in which the enlarging assembly, comprising a lamphouse, negative-holder, and lens, is mounted on a parallel motion linkage from which the focusing movement is transmitted to the objective for automatic focusing thereof, a cam co-acting with the lens carrier or a part fixed thereto is pivoted to the linkage near the assembly and is jointedly connected to an arm of the linkage so that when the enlarging assembly is lifted or lowered the jointed connection transmits rotary motion to the cam which thereby automatically adjusts the lens. A slidable platform may be arranged below the enlarging assembly and connected to the linkage by a mechanism which varies the position of the platform to maintain it central with respect to the optical axis. As shown, the lamphouse 16, negative-carrier 8, and objective 1, forming the enlarging assembly, are mounted on a support 4 pivotally connected by two pairs of equal parallel arms 5, 5a to a pillar 6 rigidly mounted on a base 29. A cam 11 is rotatably mounted on the pivot 7a of the linkage, and jointedly connected by an arm 13 to an arm 5. The objective 1 has screw-thread adjustment in its carrier 3, which has a roller 12 engaging cam 11. The linkage may be clamped by a slotted rod 33 and a screw 34. Displacement of the projection table 26 is governed by a cam 19 fast with an arm 5a actuating a spring-biassed lever 20 pivoted to the pillar 6 and linked to a bell-crank lever 23 with a wheel 24. A spring- loaded chain 25, attached at one end to the base 29, passes round wheel 24 and is secured to a cradle 28 supporting the platform 26 and running in guides in the base under the opposed actions of chain 25 and of return-springs. The Specification as open to inspection under Sect. 91 states that the weight of the enlarging assembly may be balanced by springs or counter-weights, that the pivot 14 of the link 13 may be eccentric for adjustment, and that the platform 25 may be rotatable on the cradle 28 and locked thereto by a releasable lever. This subject-matter does not appear in the Specification as accepted.