272,467. Royal Typewriter Co., Inc., (Assignees of Degener, G. 0.). June 10, 1926, [Convention date]. Adding and subtracting apparatus with several totalizers; attachments to typewriters.-In a computing-attachment provided with a column totalizer and a grand totalizer and wherein means are provided for automatically checking the entry of the column total into the grand totalizer, an incorrect entry results in the prevention of any further key actuation and the error-check mechanism is disabled when the column totalizer stands at zero, thus enabling single items to be entered directly into the grand totalizer. Other improvements concern the control of the keys by the columnar positions of the totalizer carriage, aligning means for the totalizer wheels, the position of the add or subtract lever and means whereby the latter is automatically restored to the add condition bv the return of the carriage. Specifications 281,682, 281,683, 281,684, 297,717 and 298,095 are referred to. General arrangement. The computing mechanism is contained in a casing 1, Fig. 1, the narrow front portion of which receives the spindles 13 rocked by the depression of the corresponding numeral key levers H through connections 15, 14, Fig. 3. Actuation. To each spindle 13 is connected by an arm 16, Fig. 3, a sliding bar 17 toothed at 23 to engage a cam gear 21 controlling the actuation of the master wheel. Carried by each gear 21 is a cam 26 adapted to rock an universal spring-controlled flap 27 and so through an arm 29 and pin 30 to operate a spring-controlled lever 31 contiolling an aligning pawl 38 co-operating with a totalizer pinion three or four places to the left of the master wheel. Thus as the actuating stroke terminates, the flap is freed by cam 26, and the pin 30 strikes the lever 31 and causes the pawl to engage the pinion. During the return stroks the flap is maintained depressed to keep the pawl in engagement. Control of the keys by the totalizer carriage. 'The two totalizers are mounted in a carriage 12, Fig, 3, laterally stepped by rack and pinion 42 connected with the typewriter carriage. Mounted on the carriage 12 is a comb plate 74 having tines 75, Fig. 8, at predetermined intervals corresponding with the spacing of the digit columns. Co-operating with this comb plate is a dog 67, maintained at right angles to the plate by means of spring-controlled arms 69 and mounted on a slide 64 linked at 63<1> to a frame 60 pivoted at 53. Another frame 52 also pivoted at 53 has one arm 54 engaging a spring wire 56 secured to the frame 60 while its other arms 51 lies against a roller 50 carried by a spring-controlled frame 45 pivoted at 47 and engaging all the rack-bars 17. When any numeral key is depressed therefore, the rocking of the various frames slides the dog 67 towards the comb plate 74, and if the carriage is in the right position for the entry and typing of a figure the dog will be stopped by a tine 75 and the frame 60 prevented from further displacement. If, however, the totalizer carriage position corresponds with a decimal point or a comma, the frame being unobstructed by a tine 75 is fully rocked and an arm 76 of the frame descends into the path of the frame 45 and prevents its rearward movement and therefore also the actuation of the totalizer and the printing of the digit. To disable this control mechanism, a key 77, Fig. 1, may be depressed so as to retain the arm 76 raised irrespective of the relative position of the comb plate 74. Add or subtract setting. The conditioning of the computing mechanism for adding or subtracting is effected in a known manner by an arm 82, Fig. 2, connected by a lever 86 and the parts shown, with a setting-lever 94. When the typewriter carriage is returned a pin 106, Fig. 1, rotates bv means of a cam 105, a shaft 104 and thereby through a cam 107, Fig. 4; rocks a lever 102 to return the setting-lever 94 to the add position. Error-checking mechanism. In the normal action, when the grand totalizer reaches the computing-zone the totalizer carriage rocks a bellcrank lever 112, Fig. 13, to remove a hook 117 from beneath an arm 118, Figs. 2 and 4, forming part of a frame 120 pivoted at 101 and provided with a rearward arm 121. If the column totalizer has not been used and an entry is to bemade direct into the grand totalizer, this hook must be prevented from releasing the arm 118. As already described, the actuation of the totalizers is accompanied by a rocking of the flap 27, Fig. 4, and this causes through a pin 125 a displacement of a lever 123 provided with an offset 127 lying immediately in rear of the hook 117. This hook is loosely suspended at 115 and tends to move rearwardly under the pull of a spring 128. When a number is entered in the column totalizer the lever 123 rocks and the hook is drawn forward so as to be clear of a thickened portion of lever 118. Consequently when the grand totalizer reaches the computing zone the bell-crank lever 112 effects the release of the lever 118 and the error-check mechanism becomes operative. If on the other hand no entry is made in the column totalizer, the hook 117 is not disturbed and the thickened portion prevents the release of lever 118 and the errorcheck mechanism is therefore inoperative. When the lever 118 is released it falls, due to a spring 119, Fig. 4. and rocks a lever 133 pivoted at 132, Fig. 13, so as to shift a lever 137, Fig. 3, to the right to connect it by a pin 138 with the adjoining lever 45 rocked at each key actuation as above described. The resulting movement of the lever 137 also rocks a lever 142 connected with a frame 147, Fig. 6, having upstanding flanged fingers 148 notched at different heights as shown at 149. Passing between these fingers are the rack-bars 17 each furnished with a lug 150. Normally the frame 147 occupies a position allowing free movement of the rack-bars, but when the error-check mechanism has been released, by the entry of the grand totalizer into the computing- zone, the falling of lever 118 connects lever 137 with lever 145 to cause the frame 147 subsequently to be raised. At the same time anotherarm 134<1>, Fig. 4, rigid with lever 133, moves laterally the arms 144, 145 supporting the frame 147 to bring the flanges of the fingers into theplanes of the lugs 150. When a key is operated the frame thus positioned is raised and the extent of its ascent is determined bv a link 62 attached to a digit feeler 163, Fig. 3, corresponding with pins 165 on a wheel geared with the computing-mechanism as described in a prior U.S.A. Specification. If the correct key for entering the column total digit into the grand totalizer is struck, therefore, the frame 147 will rise sufficiently to bring a notch 149 into register with the lug 150 to allow this to pass. Otherwise the lug will catch against the finger flange and the frame 147 will consequently be rocked rearwardly and in its turn will rock a latch 153 from beneath a spring-controlled key-lever 158 to allow this to enter between the crowding-lock balls 20 to prevent any further key actuation. Before the computation can be proceeded with therefore, the error becomes evident and may be corrected, whereupon the lever 158 may be manually depressed and re-latehed.