GB1165863A - Control apparatus suitable for a Machine Tool - Google Patents

Abstract

1,165,863. Indexing. ROLLS-ROYCE Ltd. 4 April, 1968, No. 16326/68. Headings B3B and B3C. [Also in Division G3] An apparatus, e.g. an indexable table of a drilling machine, receives a succession of input signals, expressed as an integral number of first magnitude units, which are stored as an integral number of second units of larger magnitude the value of which differs from the value of the input signal by an error less than a second unit, the errors are accumulated and the quantity stored is adjusted to make the error more nearly zero when the accumulated error equals or exceeds a second unit. As shown, decades D1-D5 are set by dial switches 23a-23e to a desired decimal position value. The decades D1-D4 are connected in a ring circuit whereby when they are all at zero a pulse is produced on a line 20 to stop the motion of the indexable table. The decade D5 is connected through an OR-gate G1 to the decade D4 and constitutes a secondary error store. The primary error store comprises a decade D6 connected to the decade D5 by an AND-gate G2 which is opened by a signal, through a line 25, to allow a count in the decade D5 to be transferred to the decade D6. The decade D6 is controlled by an AND-gate G3 Which is enabled, by a notzero signal from decade D6 and a signal on a line 28, to pass pulses from a pulse generator 31 for storage in the decade D5 equal in number to the count in decade D6. The gate G3 closes when the decade D6 is empty. When the desired position value is set in decades D1-D5 a sequence switch (not shown) is stepped to apply the signal 28 to the gate G3 and transfer the count in the decade D6 into the decade D5. The indexing head is then rotated by pulses applied to a stepping motor and the contents of decades D1-D4 counted to zero by feedback pulses through a line 21 and the gate G1. A zero-count the signal on line 20 stops the motor and the sequence switch is stepped to apply the signal 25 to and transfer the contents of decade D5 to store D6. Subsequent holes are indexed and the process repeated until the decade D5 is over-filled by the accumulated error when the decade issues a carry pulse which through gate G1 increases the count in decade D4 by 1 unit. The residual error in decade D5 is retained and accumulated as further positions are indexed. The sequence switch can be manually operated or, in an automatic control system, operated by a limit switch responsive to withdrawal of a drill head with respect to which the indexing head is positioned. Alternatively, the whole sequence of operations, including the setting in of the position values can be controlled by a punched or magnetic tape.