GB1003451A - Method and apparatus for length measurements - Google Patents

Abstract

1,003,451. Electric selective signalling systems. STANDARD TELEPHONES & CABLES Ltd. Nov. 8, 1963, No. 44168/63. Heading G4H. To measure the length of a running thread 6; Fig. 1, carrying a series of marks 4, 5 nominally uniformly spaced along the thread, the marks are counted 16 as they pass a first detector A and a second detector B spaced from the first detector A by a distance equal to the distance that should exist between each adjacent pair of marks 4, 5 if they were accurately positioned, appropriately controls a gating circuit from a clock pulse source 8, which produces one pulse for each increment of displacement of the thread, and a reversible counter 15 whereby if two marks 4, 5 on the thread are spaced by more or by less than the correct amount a count, positively or negatively, is made of the clock pulses for an. appropriate period to assess the difference Thus, after a length of thread has been measured the count 16 of the number of marks has to be modified by the algebraic count 15 of the errors in the distances between the marks. A third detector C is provided which functions to reset the gating circuitry after each count made by counter 15. In a modification (Fig. 2, not shown) the single detector B is replaced by a closely packed row of detectors which produce the clock-pulses produced in Fig. 1 by the rotational device 8. In the preferred embodiment the marks are printed on the thread and detected photo-electrically, but magnetic marks are referred to.