Patent GB-1066503-A (GB)
Title: Improvements in or relating to optical objectives of variable equivalent focal length
Inventor: CHAPMAN ALAN
IPC: G02B15/14
Filed: 1962-11-15
Abstract: 1,066,503. Lens mounts. RANK PRECISION INDUSTRIES Ltd., [trading as RANK ORGANISATION RANK TAYLOR HOBSON DIVISION]. Nov.14, 1963 [Nov.15, 1962], No.43252/62. Heading G2J. In a zoom type objective comprising a front assembly which includes the relatively movable members A2, A3, for varying the equivalent focal length and member A1 which is axially movable for focusing the objective at different object distances, at least one of the members Al, A2, A3, as shown in Fig.1 it is member A2, is mounted on a carriage F constrained for axial movement along a guide tube D by means of three pairs of ball-mounted rollers such as F1, the two rollers of each pair being spaced apart in the direction of the length of the tube whilst the three pairs are angularly spaced around the axis of the tube, the carriage F being held against rotation relative to the guide tube D. On rotating zoom control element H, bevel gearing H2, H3 causes the rotation of a pinion H1 meshing with gear teeth D2 on tube D. As the tube D rotates it moves axially due to pin D3 thereon having a roller D4 which engages an internal cam groove G3 in a fixed outer tube. To facilitate construction of the cam groove G3 a slot is cut right through an inner part G1 which is then inserted as a liner in the outer part G. The cam groove G3 has such a shape as to ensure the correct movement of member A3 carried by the tube D. In a modification Fig. 7 (not shown), an inwardly extending projection on tube D carries a roller (C2) engaging an external cam groove (B7) on fixed tube B1. The mount E for member A2 is secured to tubular carriage F and has an outwardly extending pin E1 carrying two rollers E2, E3, roller E2 engaging a longitudinal slot D1 in guide tube D to ensure that no relative rotation occurs between carriage F and guide tube D, and roller E3 engaging an internal cam groove G2 in the fixed outer tube to control axial movements of member A2. Two of the pairs of rollers carried by carriage F have each roller mounted on a ball race the inner cage of which is secured to the carriage F or alternatively each of such rollers is journalled on two balls mounted on carriage F. The other pair of rollers F1 are carried on movable supports spring urged towards each other, each of the supports having a 45‹ inclined face in sliding engagement with a similar face on a block secured to carriage F so that the spring force urges the rollers F1 into engagement with guide tube D. The member A1 is moved for focusing by rotating element J whereupon ball type screwthread J2, J3, J5 ensures correct axial movement. In a modification, Fig. 6 (not shown) rotation of focusing element (J) causes rotation of guide tube (K) relative to fixed outer tube (K2) and, through pin (K4) and slot (K3), rotation of carriage (K1 ) provided with three pairs of rollers such as (K6). Axial movement of carriage (K1) carrying member (A1) is ensured by its roller (K5) engaging an external cam groove (G4) on an extension of the fixed member (G1). In a further form, Fig. 8 (not shown) the outer case (MM1) is rotated by zoom control element (M4), cam grooves (M2), (M3) thereon being engaged by rollers (E3), (C5) on pins which, projecting from mount (E) for member (A2) and mount (C) for member (A3), also carry rollers (E2), (C4), engaging a longitudinal slot (L1 ) in a fixed. guide tube (L). Mount (C) constitutes a carriage (C1) having three pairs of rollers such as (C3) running on the outer surface of a fixed tube (B1), and mount (E) has carriage (F) with three pairs of rollers such as (F1) running on the inner surface of guide tube (L). The mount (O) for member (A1) carries three pairs of rollers such as (03) running on the inner surface of a fixed guide tube (L2) and has an outwardly projecting pin carrying a roller (O1) engaging a longitudinal slot (L3) in tube (L2) and a roller (02) engaging a cam groove (N3) in a part (NN1) rotated by focusing control element (N2).