Patent GB-191210902-A (GB)
Title: Combined Typewriting and Computing Machine.
Inventor: FAIRWEATHER WALLACE CRANSTON
Filed: 1912-05-08
Granted: 1913-06-09
Abstract: 10,902. Fairweather, W. C., [Underwood, J. T.]. May 8. Adding and subtracting apparatus; attachments to typewriters. - In a combined typewriting and computing machine of the type described in Specifications 5557/06 and 3390/12, in which numeral keys set one of a series of pins on denominational racks which are carried forward on the movement of a general operator to limit the rotation of computing-wheels, means are provided for performing subtraction by first adding numbers which are one less than the complement and then giving the units wheel an extra step to complete the movement. Operation of the subtraction key automatically sets the "9" pin of all the racks, and the subsequent movement of the general operator turns all the wheels through nine steps unless any of the set "9" pins have been automatically restored by the depression of a numeral key which sets the pin corresponding thereto and results in an advance of the wheel an amount less than nine steps by the value of the key depressed. At the completion of a subtraction operation, the machine is returned automatically to condition for performing addition. The operation of the subtraction key 110 through its stem 114 rocks a shaft 133 which is provided with a bar 134 extending across the rear end of the denominational racks 33, and is adapted to raise the racks simultaneously so as to project the "9" pins. These pins are projected by means of a bail 134<a>, mounted on the spindle and carrying arms 117, which engages and depresses the forward ends of levers 139 connected to the racks 33 and carrying the ' 9 ' pins. A pin 116 on the key-stem through the arm 117 rocks a universal shifter bar 118 to shift endways all the shafts 48 which are adapted to be rocked on the depression of the particular key to depress, through cross-links 45, the corresponding pins 41 of the raised racks. In addition to the arms 46 which engage the links 45 in the position for effecting addition, other arms 112, 121, 123,.... are provided which are adapted in their forward position to engage with pins 113, 122, 124.... on the next forward links, the arrangement being such that the depression of the '1' key affects the link corresponding to the '8 ' key and the ' 2 ' key affects the link corresponding to the '7' key and so on. The depression of a numeral key automatically restores the corresponding depressed '9 ' pins by means of a link 138 adapted to be depressed to engage the levers 139 by means of a transverse moving link 135 which has pins 143 thereon adapted to be engaged in the subtraction position by arms 142 on the rock-shafts 48. A latch 132 is provided to hold the shafts 48 in their forward positions and is automatically released on the return stroke of the general operator by means of a hooked finger 145 on a bar 146 which is rocked by means of links connected thereto and to a cam on the transfer spindle 78 which is rotated on the return stroke. The error key 100 may also release the latch when it is depressed so as to rock an arm connected therewith. The subtraction operation is completed when the units wheel is moved through an extra step at the commencement of the return stroke of the general operator. This is effected by providing a sliding bar 158 similar to the racks 33 but having a single setting-pin 159 in line with the ' 1 ' pins 41, which pin is set when the racks are raised by the engagement with a fixed abutment 160. The forward movement of the bar 158, on the initial stroke of the general operator, rocks an arm 161 to which is attached a spring-controlled pawl 163 adapted on the return movement to actuate the units wheel.