Patent GB-810606-A (GB)
Title: Improvements in or relating to apparatus for checking recorded information
Inventor: SALMON REGINALD DENNIS
IPC: G06F3/00
Filed: 1956-11-06
Abstract: 810,606. Selective punching machines. CREED CO. Ltd. Nov. 6, 1956, No. 33805/56. Class 31 (2). [Also in Groups VIII and XL (b)] Apparatus for checking tapes comprises a perforating device, a tape sensing device, photoelectric circuits for comparing the elements sensed with the elements to be perforated and a control circuit to prevent perforation in the event of disagreement. When a typewriter key is pressed, code vanes 7-11, Fig. 1, are rotated to move shutter 204 into the path of light falling on a photo-cell 207. Shutters 208, 209 (see Fig. 2, not shown) operate when a case shift signal is inserted. The keyboard locking arrangement shown in Fig. 3 operates as follows : the locking latch 41 revolves around its pivot 81 when trip bar 38 is raised. Arm 42 which normally holds contacts 43 open is also revolved to close the contacts and complete a circuit from power source 210 through the perforator pinching magnet PM, Fig. 4, and contact A1 in its upper position. The armature of the punching magnet is directly linked to swinging frame 27, Fig. 3, which pivots causing cam track 26 (a) to enable the combination set up on code bars 18 to be read and (b) the punch interponents to be set (see Specification 797,516). Cam 56 pushes rod 57 to the left to rotate bellcrank 61 (see Specification 797,516). Reset lever 54 rotates to move locking latch 41 to disengage lever 38. Arm 42 moves back to the position shown in Fig. 3 where the contacts 43 are open and the electromagnet de-energized. Timing latch 44 prevents contacts 43 closing until the armature has completed its return swing even though the trip bar 38 is in an operated position. Arm 222 of timing latch 44 holds the contact 223 open until the swinging frame 27 returns to its erect position. Contacts 223 complete a circuit from power supply 210, Fig. 4, through tape reader feed magnet 224. Comparator circuits 211 (one for each element of the code) consist of a Wheatstone bridge containing a photo-sensitive device 207, resistors 212, 213 and contacts 214 of a tape reader. The contacts are opened for making and closed for spacing. With the contacts 214 open the resistance is equal to that of the unilluminated photo-sensitive device 207. With the contacts closed the resistance is equal to that of the illuminated device. One circuit has the two photo-sensitive devices 207 connected in parallel with resistances equal to the resistance of the two devices 207 when both are unilluminated and when one is illuminated and one is not. When the element set up on code bar 18 of the perforator is the same as the element sensed by the tape reader the Wheatstone bridge is balanced and no voltage applied to rectifier network 218. An out-of-balance voltage will appear across resistors 215 and 216 in the event of disagreement. The rectifier network provides a voltage across resistor 219 which is in the control grid circuit of valve 220 and appears as a positive voltage on the control grid. A negative bias potential 221 normally biases the valve 220 to cut off. When the valve 220 conducts the A relay in its anode circuit is actuated to change contact A1 to its lower position and complete a circuit through the perforator keyboard locking magnet KL. In the event of disagreement the punch magnet will not have time to operate before contact A1 changes to its lower position. The keyboard is locked during the insertion of a case shift signal by the mechanism shown in Fig. 5. Members 118 move to the right causing lever 121 to rotate and draw bellcrank 126 and locking bar 127 to the left under projection 129 on the unoperated perforator key bars 3 and over the projection 129 on the particular perforator key bar 3 which has been operated. When magnet KL is energized its armature 225 engages bellcrank 105 moving member 118 and locking the keyboard. A warning lamp may be fixed. The keyboard is unlocked by operating key 228, Fig. 3, to engage link 65 and open contacts 43 to cause the A relay to drop off and contact A1 to return to its upper position (Fig. 4). The magnet KL is also de-energized. Link 65 rotates arm 63 and lever 115, disengaging arm 108 and freeing bellcrank 105 to reset itself ready for the depression of another key. To have the combination perforated in the second tape and an incorrect combination fed into the tape reader unlock key 228, Fig. 3, is pressed and also inhibitor key 233 to open contacts 237 which remain open even when key 233 is released closing again only when the punch magnet PM is safely operated. To back space the tape the mechanism in Fig. 6 (B) is operated by pressing back spacing key 256 moving bar 255 to the right, thus (a) disengaging sensing member 252 and (b) disengaging the feed pawl 250 from the ratchet wheel 251, allowing the tape 248 to be reversed. To feed the tape forward one position a forward feed key 276, Fig. 6 (A) is pressed moving the armature 277. The F or L relays of Fig. 4 are operated when a key of the perforating typewriter necessitating the insertion of a case shift signal is operated and an error is found during the vertification of that operation. In the unilluminated condition devices 207 denoted FIG and LET have sufficient resistance to absorb enough of the potential applied from source 210 to prevent the operation of these relays which are in series with them. The automatic case shift insertion is described with reference to Fig. 7 (not shown) the comparator may be disabled to allow the perforating typewriter to be used for normal tape pinching, e.g. by inserting a manually operable switch at 285, Fig. 4.