Patent GB-919699-A (GB)
Title: Improvements in or relating to vision-testing apparatus
IPC: A61B3/032
Filed: 1959-06-05
Abstract: 919,699. Sight testing apparatus. FLEMING Ltd., J. & R., FLETCHER, R. J., WORTH, C. J., and SUTHERWOOD, G. R. May 30, 1960 [June 5, 1959], No. 19392/59. Class 97 (1). Vision-testing apparatus comprises a viewing window having associated with it, for alternative use, a distance lens or lenses and a reading lens or lenses, the principal axes of the distance and reading lenses being relatively inclined, and a carrier rotatable on a shaft step by step to present a first succession of vision-checking cards to both to be viewed through the distance lens or lenses and a second succession of vision checking cards to be viewed through the reading lens or lenses. The apparatus shown comprises a casing 10 which is pivoted to a base 11 under the control of a thumb-screw 13, this casing having hinged thereto at 16 an upper part 15 and at 19 a hood 18 which carries viewing windows 17 for each eye of the patient. Behind each viewing window 17 there is disposed a pair of lenses of which the lens 20 is disposed on the distance viewing path 24 whereas the lens 21 is disposed on the reading viewing path 25, the two paths being at an angle of 35 degrees. Within the casing 10 a cylinder 31 is riveted at each side of an angular sheet 32, this cylinder being mounted on a shaft 27 which is rotatable from either side of the casing by external hand knobs 28, 29. A detent mechanism 43, 44 is provided to index the cylinder in any one of seven positions corresponding to the disposition of selected viewing cards in the light path 24, 25. These viewing cards are mounted in slides 38, on seven frames 33, each of which has angularly disposed parts 34, 35 of which the part 34 carries the cards for distance viewing whereas the part 35 carries the card for reading. A pin 59 rotates with the cylinders so as to drive a Geneva wheel 57 mounted on a pinion 62 which meshes with another pinion 63 so that the latter rotates once per revolution of the cylinders. This pinion 63 is linked at 65 and 66 to a shutter 56 which during one revolution of the cylinders obstructs the distance viewing path and at the end of that revolution flips over so as to obstruct the reading viewing path by blocking the appropriate aperture 70 in a frame 69. Thus in one revolution the reading cards can be viewed through the reading lens 21, whereas in the next revolution the distance cards can be observed through distance lens 20. Also coupled at 71 to the link 66 is a link 72 carrying a triangular plate 74, linked at 76 and 78 to another shutter 53 having apertures 54, 55, which are adapted to be disposed behind the relevant set of numerals on a dial 52 attached to each hand knob 28, 29. One set of numerals relates to distance viewing whereas the other relates to the reading cards. Lamps 81 provide for illumination of the interior of the casing. For more distant viewing a single frame 41 is fixed to the upper part 15 of the casing, the card on this frame being viewable through an aperture provided in one of the frame parts 34, and for nearer viewing one of the frame parts 35 is provided with an upstanding platform 42 for reception of a viewing card. An adjustable forehead rest 26 is provided in a hood 18 of the casing.