Pulling force P, applied to link 1, is transmitted by tie-rods 2 and 3 to helical springs 4 and 5 which are arranged between frame 6 of the instrument and movable crosspiece 7. Crosspiece 7 carries screw 8 along which nut 9 travels with lever 10 and pencil a. Pencil a moves along a chart in the direction of force application, and simultaneously in the direction perpendicular to this force by means of ratchet wheel 11 whose teeth are engaged from two sides by racks 12 and 13. The racks are attached to the body of the instrument by flat springs 14 which hold them in engagement with the ratchet wheel. When springs 4 and 5 are compressed, ratchet wheel 11 is turned counterclock-wise by rack 12; when the springs are released, it is turned in the same direction by rack 13.
$2784RG,FD$