Patent GB-522721-A (GB)
Title: Improvements relating to calculating machines
IPC: G06C7/06
Filed: 1938-12-19
Abstract: 522,721. Calculating-apparatus. WEBB, C. F. Dec. 19, 1938, Nos. 36920/38 and 3196/39. [Class 106 (i)] A multiple-bank key operated machine is provided with means for locking the keys subsequent to a failure on the part of the operator to depress a key to its full extent. If a plurality of keys is substantially simultaneously depressed and released and at least one of said keys receives an incomplete depression, all of the said keys are prevented from restoring fully to normal position and all keys except the key or keys incompletely actuated are locked against further depression. Each key bank is associated with a linkage, Fig. 2, comprising a driving bar 27 arranged for movement in a vertical plane by a bell crank 35 and T-shaped member 37 that are connected to a stop bar 43. The bar 27 is provided with hook shaped projections 40 for engagement with a hole' in a key stem when depressed. During the latter part of the downward movement of the key the stem straddles the stop bar 43 and recesses 46 therein limit the depression. The lower surface of the stop bar is formed with a notch 48 that co-operates with a pawl 49, Figs. 11 and 12, pivotally mounted on a pin 50 in the upper arm of a U-piece 51. The U-piece 51 is formed with a tail 53 that normally rests on a bar 54 extending across the machine, the bar 54 being supported by arms 55 on the spindle 52 of the U-piece 51. A bell crank lever 59 has a notched arm 60 normally engaging the iron face of the bar 54, the other arm 61 lies behind the stop bar 43. The totalizer wheel 21 is actuated by a rack 67 on an arm 69 pivoted to a U-shaped member 71. The arm 69 is formed with a slot 73 engaging a roller 74 on a pivoted arm 75 connected by a link 77 to an arm of the T-shaped member 37. The member 71 has one arm formed with a right-angled slot 82 into which extends a projection 83 of a longitudinally pivoted bar 78, Figs. 2 and 5. The bar 78 is formed with projections 79 for engagement with the key stems when a key is fully depressed. On complete depression of a key the bar 78 is rocked thereby moving the extension 83 out of the vertical part of the slot 82 whereupon a spring 85, connecting a hook on an arm of the member 37 to an extension 84 of the member 71 releases the member 71 so as to move the set rack 67 into engagement with the totalizer wheel. The rocking of the bar 78 through a projection 81 depresses the pawl 49 away from the stop bar 43 so that on release of the depressed key the parts actuate the totalizer and return to normal position. A pin 87 on the stop bar 43 engages the extension 84 to restore the member 71. Incomplete depression of a key fails to operate the bar 78 so that when the key is released and the stop bar 43 starts to move rearwardly it picks up the pawl 49 and swings the U-piece 51 into the position shown in Fig. 12. In this position the arm 61 of the bell crank 59 engages a pin 44 and prevents the stop bar 43 returning to home position. This failure is indicated by the depressed key restoring to a position below the normal and prevents the other keys in that bank being depressed. Downward movement of the bar 54 also serves to release the other bell cranks 59 and set the arms 61 in front of the pins 44 to hold the stop bars 43 against movement. The complete keyboard with the exception of the key depressed is thereby locked. Full depression of the key corrects the error and locks the entire keyboard. Unlocking of the keyboard is effected by operating a handle 65, Fig. 18, which actuates a pivoted release bar 63 to restore the bell cranks 59, the bar 54 and linkage 27, 43. When a plurality of keys is depressed simultaneously and released and one or more of such keys receives an incomplete depression all of these keys will fail to restore completely. Subsequent operation of the handle 65 will free the keys with the exception of those incorrectly actuated. The error can be corrected as above described and the handle 65 again operated to free the keyboard. If, during depression of a key, another key in the same bank is moved accidentally this movement has no effect on the calculation due to the initial displacement imparted to the bar 27 by the depression of the correct key. Specifications 514,289 and 514,290 are referred to.