Patent GB-553581-A (GB)
Title: Improvements in printing mechanism for machine compiling statistics from record sheets
IPC: G06K17/00
Filed: 1941-12-19
Abstract: 553,581. Printing mechanism for statistical machines. INTERNATIONAL BUSINESS MACHINES CORPORATION. Dec. 19, 1941, No, 16419. Convention date, Dec. 27, 1940. [Class 106 (i)] [Also in Group XV] Relates to machines for obtaining statistics from examination tests of the true-false type in which a record is made in one of several positions on a response sheet, and consists in providing a plurality of resistors which are selected in accordance with marks on a record sheet, and includes a printing wheel rotatable to different value positions, said resistors being in one arm of a Wheatstone bridge and the wheel connecting other resistors in another arm of the bridge until the bridge is balanced, whereupon printing takes place from the rotating wheel. The " sensing," resistor " and " selector" units 50, 66, and 72 are as described in Specification 530,093, the " sensing" blades 54 extending into slidable caps 55 which contact with " resistor " elements 69 and these in turn with the caps 77 of " selector " elements 76. As in the abovementioned Specification, the response sheet R, Fig. 5, is placed in the chute 97 with the pencil marks representing the answers facing the " sensing " blades. A key sheet k and secondary keysheet SK are placed in the key-sheet holder 22 and the latter placed in the carriage 34 which is then moved to the left, Fig. 1, to engage the selector elements. Selector elements. - The pins 76 have an enlarged centre formed of end conducting pieces and a central insulating piece. They are each engaged by strips 92, 93 on either side. If the pin is in the position of the top pin in Fig. 10, i.e. registering with holes in both key sheets, then strip 93 engages a conducting part of the pin and a circuit is made. If pin 76 is in the position where the secondary sheet SK blocks it, as with intermediate pins, Fig. 10, the strip 92 makes contact. If the pin 76 aligns with a perforation in the sheet SK but not with a perforation in sheet k as in the case of the bottom pin, Fig. 10, the strips 92, 93 engage the insulated part and there is no circuit. On depression of an operating key 99 the circuit of the motor M is made and the clutch disc 122 drives through half a revolution to work a toggle mechanism to move the platen 146 and press the sheet R against the sensing blades. The pencil marks control the circuits. On depression of the key a second time, the shutter for the chute is withdrawn and the card drops into a hopper. Printing unit. - The mechanism according to the present invention is driven by a motor M1 energized upon closure of contacts 300 by a key 301. A pinion 302 on the motor shaft drives a wheel 303 free on a shaft 304 and integral with a ratchet 305 adapted to be engaged by a spring-pressed clutch dog 306 pivoted to a disc 307 fast on the shaft 304. When the key 301 is depressed, the disc 307 and dog 306 are released the dog engaging the ratchet and the key is held depressed by the periphery of disc 307 engaging the extension 309. Just before completion of a revolution of shaft 304, a disc 310 and a tooth 311 on shaft 304 come into operation. The tooth 311 engages an idler pinion 312 and through it rotates a gear 313 one step to rock the shaft 314 through one-tenth of a revolution. The pinion 313 is normally held by a spring detent 315 on a vertically slidable frame 316 also carrying a roller 317. The timing is such, that as the roller 313 is in the depression on disc 310, the detent 315 is drawn down to permit rotation of the wheel 313. On the shaft 314 is a disc 318 which on rotation maintains the key 301 depressed, the shaft 304 making a second revolution. When it has made ten revolutions the shafts are in the relative positions of Fig. 22 and the key returns under its spring 308 opening contact 300. The shaft 304 drives through bevel gear 320, 321 a vertical shaft 322, Fig. 21, to the lower extremity of which is secured a type wheel 323. The shaft 314 drives through bevel gears 324, 325 a sleeve 326 carrying a type wheel 327. Thus numbers from 1 to 99 may be presented to the printing hammer 328. The hammer 328 is pivoted at 329 and has connected thereto at 330 a member 331. A lateral extension 336 on a cam follower 335 is rocked by a cam wheel 334 on shaft 304 ten times for one revolution of the shaft 304. When the magnet 338 is energized, the armature lever 337 is rocked so that the extension 339 of member 331 is in the path of extension 336 and the hammer 328 is rocked to impress the type wheels A magnet releases a spring catch 340 which has dropped down behind the pin 330 and allows the hammer to be restored by the spring 332 An inking ribbon 342 is provided. Secured to the shaft 304 is a group of nine cams 343. These serve to close pairs of contacts 344 in succession until all are closed, and then to reopen them. On shaft 314 is a similar group of nine cams 345 which close contacts 346 in succession and then open them. The timing is such that the contacts 344 first close in succession with all contacts 346 open, and then contacts 344 close in succession a second time with the first contacts 346 closed and so on. On shaft 304 are three additional contact opening cams 347, 348, 349 for contacts 350, 351, 352. There is also a shaft 304 on cam 353 for controlling contacts 354, and on shaft 314 a cam for controlling contacts in a supply circuit. In Fig. 1, the printing wheels lie against the sheet R after insertion, the chute 97 being cut away to allow operation of the hammer 328. The printing unit is made shiftable so that numerals may be printed in any of several positions on the sheet. The strips 92, 93 from the selector pins or elements 76 are connected up in circuit with similar strips from a set of field-determining pins similar to the selector pins co-operating with holes near the edges of the key-cards. A master switch 180 is provided and "formula" switches 181A, 181B, 181C which are set to control the kind of statistics it is desired to obtain. Two potentiometer resistances 201, 202 form two arms of a Wheatstone bridge, Fig. 18a, while the resistors 69 form a third arm and the cam operated resistances 361, 362 form a fourth arm. The bridge arrangement is such that when an examination sheet R is sensed, a number of resistors 69 are connected in parallel into an arm of the bridge, as indicated by the four resistances designated "right." When the printing mechanism is placed in operation, resistances 361 are successively connected in parallel with the other arm of the bridge. As long as the bridge is unbalanced, current flows through the diagonal to energize a coil 363. This will prevent tripping of the hammer. When the bridge is balanced, current fails to pass through the coil 363 and this condition will be detected and other circuits called into operation to energize the printing magnet, so that the hammer will print on the sheet R a number corresponding to the value of the resistors 361 required to balance the bridge. Where the marks sensed are classified as " right " or " wrong " responses, a number of resistors 69 representing " right answers is connected in the arm and a number of resistors 49 representing "wrong' answers into the opposite arm, the bridge being balanced according to the difference. A circuit diagram is described involving the use of a thyratron valve. U.S.A. Specification 2,113,620 also is referred to.