Mechanism to open and close iris on lens
AssigneeAddressograph Multigraph Corporation
InventorsRobert J. Cieplik, Victor Czarnecki
Life of this patent
Estimating the term…
Abstract
Some photocomposition machines use optics with a variable magnification lens, usually referred to as a variator lens. Because larger size print requires more lumens of power for proper exposure of the photosensitive sheets used in photocomposition machines, the common practice is to employ an iris diaphragm which is coordinated with the size of the projected image. The ratio of the diaphragm opening to the focal length is referred to as the f-number. The invention shows an improved cam operated iris control wherein the cam-to-follower pressure angle is maintained at a minimum and provides a means for enabling the cam follower to traverse the entire cam without binding as the cam follower carriage is moved relative to the driving cam.
Claims3
A cam and cam follower lens system, comprising:
- a lens, an iris diaphragm that can be turned by a ring so as to change the diameter of a central opening, said diaphragm and lens mounted on a carriage in juxtaposition whereby the diaphragm effectively controls the aperture of the lens;
- an iris diaphragm ring having a drive receiving gear configuration, an idler gear engaged with said diaphragm gear;
- a follower arm having a first end which is a gear segment and a second end which is a cam follower wheel, a means for pivotally mounting said arm with the gear segment engaged with said idler gear;
- a cam track means for driving said follower arm and iris diaphragm to a predetermined aperture opening by moving said carriage along a path paralleling said cam track, said cam track means consisting of a pair of surfaces, one of said surfaces being a generated cam surface and the other being a confining surface, said surfaces closely spaced to a clearance of about 0.08 mm with respect to said follower wheel throughout a calculated f-number range wherein the pressure angle of the cam surface and wheel is not greater than 40.degree., said other one of said spaced surfaces diverging to release said wheel in areas wherein an abrupt change of cam slope would otherwise result in a binding of the wheel, and
- means for engaging said follower wheel end to apply pressure to hold said wheel against the cam surface only in said released area.
A cam and cam follower lens system, comprising:
- a lens, an iris diaphragm that can be turned by a ring so as to change the diameter of a cnetral opening, said diaphragm and lens mounted on a carriage in juxtaposition whereby the diaphragm effectively controls the aperture of the lens;
- way rods defining a carriage track and means mounting said carriage for longitudinal movement on said track;
- said iris diaphragm ring having a drive receiving gear configuration, an idler gear engaged with said diaphragm gear;
- a follower arm having a first end which is a gear segment and a second end which is a cam follower wheel, a means for pivotally mounting said arm with the gear segment engaged with said idler gear;
- a cam plate extending parallel to said track, said plate having a guide slot which captures said wheel loosely held, said slot and wheel limited to a pressure angle of not more than 40.degree..
Dependencies are inferred from the claim text.