Patent GB-191213022-A (GB)
Title: Improvements in Range Finders.
Inventor: BOYUM JOHN SEVATH
Filed: 1912-06-03
Granted: 1912-12-23
Abstract: 13,022. Boyum, J. S. June 3. No Patent granted (Sealing fee not paid). Range - finders.-The instrument, which is of the coincidence type, comprises first, ranging- means constituted by a tape 138, Fig. 5, giving a range - reading, and actuated from the handle 119, Fig. 7, which sets the separating - prisms 66, 67 in and out along the axial line of the eyepiece 32, and, secondly, means for adjusting the instrument when sighting an infinity bar in the usual manner, the infinity adjusting- means being locked while ranging means are being operated and vice versa. In ranging, rotation of the handle 119 drives the spindle 111 by means of bevel - wheels 116, 114, and from this spindle, motion is transmitted to the tapemoving mechanism by bevel - wheels 115, 158 and to the carriers 68, 69, Fig. 8, of the prisms 66, 67 by spur gearing 110, 108, which drives the screw 70, Fig. 8, passing through the carrier 69, to which the upper carrier is attached by means of a spring 83. When coincidence is obtained, pressure on the finger - piece 136 within the handle raises the plunger 123, rocks the shaft 128 about its pivot 129, causing a rod 185 to remove the screw 179 from before the sight aperture 180, and causing a brake to be applied to the inner periphery 159 of one of the wheels 154 of the tape-winder. The button 136 can then be turned aside till a flange on it engages with a flange 137 and it is held in its raised position, whereupon a reading can be taken at leisure. When it is desired to adjust the instrument, the handle 119 is rotated to bring about sighting for infinity. During the setting, a nut 161 carrying a fork 162, Fig. 21, travels along the threaded portion 160, of the spindle 111 until, the fork contacting with a stop 166, on a screwed spindle 163, the spindle 163 is moved, and, by means of an arm 175, the spindle 169 is rocked, causing the lug 176 to turn and force the brake block 167 into contact with the surface 159 to arrest the tape. When the operator appreciates the resistance thus introduced, he makes the correct setting and then turns the handle 229 into the position shown in full in Fig. 21. By this means, through bevel-gearing 226, 222 and cranks 220, 219, the shaft 215 is rocked, causing the rod 241 to pass through holes in register in the wheels 153, 153<a> and so positively lock the tape-winder, and also, by means of cranks 216, 209, raising the shaft 206 so that the milled head 248 from which the infinity adjustment is effected is elevated above the casing of the instrument. Infinity adjustment is effected by giving the carriage 68 a differential movement with respect to the carriage 69, by means of the screw 191, Fig. 5, which passes through a lug 189 on the lower carriage and bears on the upper carriage, and is so driven from the shaft 206 that, while rotation is transmitted to it by means of the two square shafts 194, 198 connected by a member 199. yet during adjustment in ranging. the shaft 194 can slide through the member 199, which has only a loose fit, means being provided in the head 262 on the shaft 206 to introduce sufficient backlash after infinity adjustment to release the pressure. Adjustable stops 44, 46, Fig. 5, are provided to define the limits of the adjustment of the eyepiece for reading on the infinity bar and for ranging and, when the part 33, Fig. 8, is racked back for reading on the bar, a partitioning septum 281 is depressed to separate clearly the rays coming from the two prisms 66, 67. A system of mirrors is used which gives a finder image through the sighting- orifice 296, this system being adjustable by means of rack and pinion 299, 300 from the milled head 303. By the provision of a second stop 165, Fig. 21, attention can be directed as before to the fact that the tape is nearly unwound from one spool.