A device for continuously altering the focal length of photographic lenses

Claim 1

A device for continuously altering the focal length of photographic lenses adapted to be detachably mounted between an objective lens unit and a camera body, comprising: a cylindrical casing 1 detachably mounted to said camera body; an operating ring means having an outside Threaded portion 2b and an inside threaded portion 3a, said outside threaded portion 2b rotatably screwed into aid cylindrical casing 1; a first cylinder 7 for mounting said objective lens unit A screwed into said operating ring means so as to be movable only in the direction of the optical axis of said objective lens unit A; a second cylinder 8 disposed in said first cylinder 7 in concentric relation with said optical axis and integrally coupled to said operating ring means; a third cylinder 9 mounted in said second cylinder 8 so as to be movable only in the direction of said optical axis by the rotation of said second cylinder 8; an auxiliary lens group supported relative to said third cylinder 9; a diaphragm actuating rod means comprising a gear cylinder 11 disposed in the space between said first cylinder 7 and said second cylinder 8 and meshed with said operating ring means; a threaded tube 12 screwed into said gear cylinder 11 and supported by said first cylinder 7 so as to be movable only in the direction of said optical axis; a threaded rod 17 screwed into said gear cylinder 11 and supported by said cylindrical casing 1 so as to be movable only in the direction of said optical axis; a diaphragm operating lever 16 built in said objective lens unit A; a pressure ring 14 secured to said first cylinder 7 for urging said threaded tube 12 toward said camera body B and also adapted to operate said diaphragm operating lever; the spiral of said outside threaded portion 2b and that of said inside threaded portion 3a being so formed that the directions of said two spirals are opposite to each other, and the spirals of said threaded tube 12 and said threaded rod 17 being so formed that the directions of said two spirals are opposite to each other, whereby said first cylinder 7 and said threaded tube 12 are moved forwardly or backwardly along said optical axis in the same direction by an equal amount when said operating ring means is rotated.

Claim 2

A device for continuously altering the focal length of photographic lenses adapted to be detachably mounted between an objective lens unit and a camera body, comprising: a cylindrical casing 1 detachably mounted to said camera body; an operating ring means having an outside Threaded portion 2b and an inside threaded portion 3a, said outside threaded portion 2b rotatably screwed into aid cylindrical casing 1; a first cylinder 7 for mounting said objective lens unit A screwed into said operating ring means so as to be movable only in the direction of the optical axis of said objective lens unit A; a second cylinder 8 disposed in said first cylinder 7 in concentric relation with said optical axis and integrally coupled to said operating ring means; a third cylinder 9 mounted in said second cylinder 8 so as to be movable only in the direction of said optical axis by the rotation of said second cylinder 8; an auxiliary lens group supported relative to said third cylinder 9; a diaphragm actuating rod means comprising a gear cylinder 11 disposed in the space between said first cylinder 7 and said second cylinder 8 and meshed with said operating ring means; a threaded tube 12 screwed into said gear cylinder 11 and supported by said first cylinder 7 so as to be movable only in the direction of said optical axis; a threaded rod 17 screwed into said gear cylinder 11 and supported by said cylindrical casing 1 so as to be movable only in the direction of said optical axis; a diaphragm operating lever 16 built in said objective lens unit A; a pressure ring 14 secured to said first cylinder 7 for urging said threaded tube 12 toward said camera body B and also adapted to operate said diaphragm operating lever; the spiral of said outside threaded portion 2b and that of said inside threaded portion 3a being so formed that the directions of said two spirals are opposite to each other, and the spirals of said threaded tube 12 and said threaded rod 17 being so formed that the directions of said two spirals are opposite to each other, whereby said first cylinder 7 and said threaded tube 12 are moved forwardly or backwardly along said optical axis in the same direction by an equal amount when said operating ring means is rotated.