Interpolator for a numerically controlled machine with step size selected in response to feed rate

An interpolator responsive to a set of input signals for each block for successively producing a plurality of distribution signals for a numerically controlled machine, said input signals comprising a set of displacement signals and a feed rate signal, said displacement signals being representative of conventional displacement data specifying said each block in terms of a conventional step size, said feed rate signal being representative of a feed rate defining, in turn, a conventional pulse distribution rate, said distribution signals being representative of those commanded positions substantially along said each block which said numerically controlled machine should follow at said feed rate, wherein the improvement comprises:

• step size means responsive to said feed rate signal for selecting a working step size to produce a step size signal representative of said working step size;
• working data means responsive to said step size signal and said input signals for producing working signals representative of working displacement data and a working pulse distribution rate, the ratio of said working displacement data to said conventional displacement data and the ratio of said working pulse distribution rate to said conventional pulse distribution rate being substantially equal to the ratio of said conventional step size to said working step size;
• and
• pulse distribution means responsive to said working signals for producing said distribution signals at said working pulse distribution rate, said distribution signals being now representative of said commanded positions in terms of said working step size.