Patent GB-474096-A (GB)
Title: Improvements in sight testing instruments
IPC: A61B3/103
Filed: 1936-07-10
Abstract: 474,096. Recording-apparatus. REASON, R. E., and KAPELLA, Ltd. July 10, 1936, No. 19096. [Class 106 (iv)] [Also in Group XX] Sight-testing apparatus having adjustments, one for measuring the power of the eye and another for rotating the instrument relatively to the eye, is provided with recording means comprising a marking device and a holder for a record sheet &c. mounted for relative traversing movements derived from the said adjustments, and manually-controlled printing means whereby the sheet may be marked each time an observation is to be recorded. The Figures show the invention applied to an optometer of the kind described in Specification 437,764 in which the optical elements are contained in two casings 1, 4 and the power is measured by adjusting one casing relatively to the other along their common axis, i.e. by displacing the casing 4 along the rod 2, and the rotational adjustment is obtained by turning an internal prism by a wheel 5. Figs. 1 and 2 show a form of the invention in which the record consists of markings on a sheet of polar graph paper mounted on a rotatable holder 6 connected by a belt 7 to the wheel 5. The stylus 11 is carried on the casing 4 by a lever 12 pivoted in a slot 14 in a plate 15 so that the stylus moves in a straight line along a radius of the holder 6. The lever is actuated by a plunger 19 having a roller 21 engaging a cam surface 20 on a wheel 23 which is pressed by a spring 32 into frictional engagement with a disc 31 secured to a shaft 24 on which is a pinion 25 operated by a rack bar 26 attached to the casing 1. The cam wheel 23 can be rotated manually over the disc 31 to enable any desired part of the power range to be recorded. The stylus is pressed against the paper by pulling on the lower end 35 of the plate 15. If squared paper is to be used the holder 6 is replaced by a cylindrical paperholder rotatable about its vertical axis. If the power adjustment of the instrument follows a non-linear law, a scale-converting mechanism may be provided between the adjustment and the stylus. As shown in Fig. 5, such mechanism comprises a cam 40 and arm 41 replacing the pinion 25 and rack 26. The arm drives the cam by tapes 42, 43, the tape 42 being anchored to both arm and cam and the tape 43 being anchored to the cam and connected to the arm by a spring 47. Figs. 7 and 8 show a numerical recorder comprising two scaled type discs 61, 62 independently mounted on a spindle 60 on the casing 4, and an index disc 63 fixed to the spindle. The disc 61 is connected to the wheel 5 by a belt 64 and the disc 62 is rotated according to the power adjustment by rack and pinion 67, 68. The record paper 69 is drawn from a spool 70 over rollers 71, 72 and passes over a plate 74 and through a slot 73 in the casing 4. The paper is advanced for each record, and the record is made, by depressing a spring plunger 76 carrying a plate 77 to which are pivoted two pawls 79, 80 which push the paper over the plate 74. When the paper is sufficiently advanced, the pawls are disengaged by an arm 82 striking an abutment 83, and a projection 84 on the plunger engages a cam surface 85 and causes a pad 88 to press the paper against the type wheels. Inking is effected by a typewriter ribbon 91, the take-up spool of which is slowly rotated by the paper-spool shaft through gearing 94, 95.