GB1367934A - Method of and apparatus for positional detection in a machine - Google Patents

Abstract

1367934 Machine tool control MARTONAIR Ltd 9 May 1972 [18 May 1971] 15454/71 Heading B3B [Also in Division G3] A method of detecting the position of one or more movable elements 13 of a machine, e.g. a machine tool, to enable the or each element to be controlled, comprises transmitting coded fluid pressure wave pulses through waveguide means 15 to one or more outlets 14, the or each of which is occluded in one position of an element 13 and is unobstructed in another position of that element whereby the element 13 controls the emanation of a pressure wave signal 35 as a non-directional signal which permeates the atmosphere, and detecting the emanation of the or each pressure wave signal 35 with a receiver arranged in a position independent of the outlets to produce an output which varies according to the position of said element. The method uses a pneumatic supply to a transmitter 16 which produces the waves, e.g. pulses in the waveguide 15. The transmitter may be a fluidic device (37) (Fig. 2, not shown) which produces pressure wave oscillations by turbulence as air flows through channels (33), (34) and feeds its signal (35) into a transmitting horn (30). The movable element may be a plate (31) having apertures (32) shaped and spaced to vary the signal 35 from full to zero output. A receiver (20) (Fig. 3, not shown) comprises a horn (21) for receiving the signal (35) and passing through a resonator chamber (22) to a turbulence amplifier (23) that receives an input signal (29). The amplifier (23) is connected to a chamber (25) having a diaphragm (26), the chamber (25) being connected to a further turbulence amplifier (24) that produces a control signal (28) by varying an input signal (27). The arrangement provides a frequency selective decoder which passes a selected frequency at the resonant frequency of the diaphragm. The transmitter 16 may produce pulses in predetermined sequences and frequencies or in groups, the receiver discriminating between groups and sequences and frequencies coming from a plurality of transmitters to control a particular element 13, e.g. through an actuator.