GB1225121A - - Google Patents

Abstract

1,225,121. Counting apparatus. ENGLISH NUMBERING MACHINES Ltd. 5 July, 1968 [20 July, 1967], No. 33377/67. Heading G4D. In a device for producing a check digit or symbol comprising a check digit wheel 1 having check digit carrying print faces 2, a pawl tooth 5b of a comb pawl 5 (Fig. 6) steps a ratchet la driving the check digit wheel, and a pawl tooth 5a of the comb pawl steps a ratchet 6a driving a control wheel 6, the comb pawl being prevented from stepping the check digit wheel through one step when the wheel 6 passes through a predetermined position. The tooth 5a is longer than the tooth 5b, and the ratchet 6a driving the control wheel has a land 7 of reduced depth, so that when the longer tooth 5a engages the shallow land 7 (Fig. 2), the shorter tooth 5b is held clear of the ratchet 1a and is unable to rotate the check digit wheel 1 (Fig. 3). Rotation of the control wheel 6 steps the unit wheel of a numbering box. The check digit wheel moves in step with the unit wheel, except at a decade change on the numbering box, which corresponds with the engagement of the longer tooth 5a with the shallow land 7, when the same check digit is displayed for two consecutive numbers. Check digit wheels having 13, 11, 10 or 7 digit carrying print faces for moduli 13, 11, 10 or 7 are described.