Patent GB-240889-A (GB)
Abstract: 240,889. Lindahl, A., and Luttropp, C. May 8, 1924. Adding, subtracting, multiplying, and dividing apparatus; differential mechanism; displaying items; error keys. - In a single key-bank independently operated machine for performing calculations according to the four rules the differential mechanism comprises a rotatable selector having groups of vertically disposed stops adapted to be adjusted to operative position in successive groups in accordance with the key depressed so as to limit the axial movement of a corresponding transmission pinion when the main handle is operated. The pinions co-operate with an item indicator and with a variably toothed drum the rotation of which transmits the setting to the totalizing-counter. The keyboard comprises ten numeral keys and a set of control keys for setting the machine for adding and multiplying, subtracting and dividing, repeated addition, correcting errors, and tabulating. Each numeral key is connected by a bell crank lever 95 and link 94 to a corresponding lever 92, Figs. 4 and 7, pivoted on a common pin 93. The levers 92 engage pins 90, 91 depending from spring-controlled escapement pawls 85, 86 that co-operate with the ratchet teeth 841 of a toothed ring 84 secured to the selector 3, Figs. 4 and 15, and each lever when rocked by the depression of a key permits a step-by-step movement of the selector 3. At the same time a projection 96 on the actuated lever 92 moves the appropriate stop 79 in the selected column to the operative position. The selector movement is effected by means of gearing 97, 99, 100, and rack 101 under the control of a spring 102, Fig. 19. Around the selector is arranged a number of denominational spindles 5 each having a pinion 59, Figs. and 15, for engaging one or other of the toothed rings of the stepped drum 4. The spindles are guided by a rod 64 and are held in depressed position against a spring 63 by means of a flange ring 65. When the main handle 2 is operated the cam 392, Fig. 10, on the main shaft 32 frees the projections 303 on a bifurcated link 39 attached to a spring-controlled lever 73 to allow the lever to rise and thereby, through the link 69, arm 67, and guides 66, to raise the flange 65 and free the spindles 5 until arrested by the projected stop 79. The link 69 has a notch in which rests normally the end of a catch lever 71 pivoted on the lever 73. The spindles 5 in those denominations above the highest significamt figure are locked in their lowermost position by means of a flange 83 on the base of the selector, the flange extending from the first to the last spindle 5. The stepped drum 4 is fixed to a spindle 48 and is adapted to be rotated in one or other direction for addition or subtraction by bevel wheels 46, 47 through a clutch 49 and a bevel wheel 45 on the main shaft 32 which receives motion through a one-way ratchet drive from a pinion 31 in gear with a sector 30 on the main oscillating handle 2. Rotation of the drum 4 imparts differential movement to the pinions 59 and so through bevel gearing 120 - - 124 to the actuating pinions 125 of the totalizing- counter 126. The differential setting of the spindles 5 is transmitted to an item indicator 6 by the guide rod 64 through a bell crank 128, rack 129 and gearing 130 - - 132. At the end of the forward stroke of the handle 2 the set parts are returned to normal position. A pin on the sector 30 first operates to depress the lever 73 to return the flange 65 and reset the spindles 5, the flange being locked by the engagement of the cam 392 with the projection 393. On the return of the sector 30 a pawl 108 pivoted at the end of a link 104 attached to the sector engages the end of the rack 101 to return the selector to normal position. The pawl 108 carries a pin 109 that rides in a slot 106 in a plate 107, the slot having a depression 115 to free the pawl 108 at the normal position. In multiplying operations the repeat key 24 is depressed to operate a link 74 to free the catch lever 71 from the link 69 so that depression of the lever 73 during an operation does not effect the resetting of the flange 65 and spindles 5. At the same time a link 114 connected to a pair of bell crank levers 111, 112 depresses the slotted plate 107 to prevent the engagement between the pawl 108 and rack 101 so that the selector remains in set position. Release of the repeat key allows the catch 71 and pawl 108 to become operative to restore the parts during the last operation of the main handle. On the return of the selector to normal position the projected stops are returned by means of a fixed angular member 116, Fig. 4. To correct an error the errors key 25 is depressed whereupon a link 134 actuates a lever 135 carrying a pawl 136 so as to throw the pawl into engagement with the teeth 137 of the rack 101 to return the sector one step backwards and reset the erroneous stop.