Patent GB-141126-A (GB)
Title: Improvements in and relating to devices for use in plotting terrain
IPC: G01C17/12
Filed: 1919-01-06
Abstract: 141,126. Fanning, S. H. Jan. 6, 1919. Maps.-A device for use by observers on aeroplanes in plotting terrain on skeleton maps &c. comprises apparatus operated by hand for traversing in either direction a map or sketch sheet in continuous strip form over a supporting- surface beneath a sight opening, the parts being enclosed in a casing which is supported so that it can be turned about two axes at right-angles to each other, one movement providing for reversing or otherwise angularly adjusting the map &c., and the other movement for varying the inclination or dropping the device aside when not in use. A sliding cover having a window is provided for protection against rain &c. An electric lamp may be provided on a bracket. Two examples are given, Figs. 3, 5, and 8 showing one example, and Fig. 11 the other, the details being as follows :-(1) The strip 36, Fig. 3, is wound on rollers 52 and guided by rollers 51 over a supporting-plate 37, these parts being enclosed in a metal casing having an open top 1, side walls 3, end walls 6 having doors 7 for access to the interior, and a bottom 4 which is carried by a turntable mounted on a bracket 33 attachable to the fuselage of the aeroplane. The rollers 52 are connected to pinions 63 alternately engaged, according to the direction of drive, by idle pinions 64 on a rocking member 65 on an operating-shaft 66, which carries a gear wheel 67 in constant mesh with the idle pinions, and is provided with a handle at each end. The gearing is enclosed in a separate casing on one side wall of the main casing. In the alternative arrangement shown in Fig. 11, the roller apparatus is carried by a removable inner casing 44<1> having a top 45<1> serving as the map support. The operating-shaft 84<1> extends through guidemembers 86<1> having a rib 87<1> seating within a vertical slot in the adjacent wall of the outer casing. (2) The rollers 52, Figs. 3 and 5, comprise hollow spindles having a head 56 at each end attached between a disk 58 and a thimble 54, a central opening 59 being formed through these parts to receive at one end a bearing-pin and to fit at the other end on a short spindle and lugs on the pinion 63. The thimbles 54 are telescopically mounted in the spindles and are pulled inwards by a spring 82 attached to crosspins 80 which key the thimbles to the spindle; by this arrangement the heads can yield to compensate for slight variations in the width of the strip. The bearing-pins are carried by sliding arms retracted by springs to limits determined by adjustable abutments, so that the disks 58 on the opposite ends of the spindles are pressed against friction material 70 on the casing enclosing the gearing, and the degree of pressure can be varied. In the alternative arrangement, the thimbles are fixed in the ends of the spindles, and the bearing-pins are formed on wings of a resilient metal plate attached to the inner casing, the opposite heads of the spindles bearing against friction material 101', Fig. 11. (3) The ends of the strip are tapered and secured to the roller spindle by means of a pivoted gripping-bar 85, Fig. 5, seating into a channel 84 in the spindle and retained by a spring catch; or the spindle is slotted longitudinally to receive a pivoted gripping-bar having flanges which enter the slot and are extended at one end for engagement by a collar sliding on a reduced end of the spindle. (4) The lateral margins of the strip 36, Figs. 3 and 8, on the supporting-plate 37 are engaged by friction strips 42 of felt &c. secured to flanges 34 on the side walls 3 of the casing; the outer ends of the strip 42 are anchored over metal strips 44 secured by rivets 43 between the parts 34, 37. In the alternative arrangement, the lateral margins of the strip extend under graduated scale members 49', 50', Fig. 11, which may be transparent. (5) The cover for the casing consists of a metal frame 45, Figs. 3 and 8, fitted with a pane 46 of celluloid &c. The frame slides between upstanding flanges 47 and is retained in position against stops 48 by fastenings 49. Felt or other packing 50 is provided on the underside of the frame. The cover shown in Fig. 11 has flanges 98<1> engaging over flanges 91 of the outer casing. (6) The turntable mounting shown in Fig. 3 comprises a bolt 15 having a squared portion fitting in corresponding openings in the bottom 4 and a reinforcing-strip 10, and a cylindrical portion passing through a circular head 17, which is pressed against the bottom 4 by spring washers retained by nuts, and has an annular groove receiving an annular rib 23 on the bottom 4 and formed at intervals with projections 24 to seat in depressions in the rib 23, determining for example each quarter turn. The head 17 is carried by an arm connected to the bracket 33 by a pivot adjustment comprising spaced ears 27 on the arm formed with radial teeth or corrugations, a corresponding ear on the bracket located between the ears 27, and a clamping-bolt 31 for souring the ears in engagement. The turntable mounting shown in Fig. 11 is a separate fitting, the casing having a socket 30<1> and a latch device 35<1> for detachable connexion. There are two circular heads 25<1>, 17<1> and interposed friction material held together by a pivot bolt 21'. The lower head 17<1> is mounted between pivot screws 20' in ears on an attachment plate 12<1>.