Patent ID: 7440358

Claim:
A visual indicating device comprising two or more discs each disc having a radial discontinuity to thereby form a surface of which the plane progresses in a helical manner, said discs being superposed and interleaved and lying in mutually parallel helical planes, each disc being independently rotatable about a common axis by drive means adapted to selectively rotate one or other of the discs, whereby the discs, when viewed axially face on, display overlapping visually contrasting segments having an area or position representative of the relative positions of rotation of the discs and representing a value of a parameter to be displayed by the device, wherein one disc is mounted to extend laterally from a rotatable shaft, the other disc being mounted to extend laterally from the outer surface of a rotatable cylinder within which the shaft rotates, the shaft being mounted coaxially within the cylinder, with the cylinder having a helical slot through which an inner portion of the one disc adjacent the shaft extends, rotation of the shaft relative to the cylinder producing relative axial movement between the shaft and the cylinder by virtue of the disc moving in the slot in the cylinder and causing the one disc which is overlying the other disc to mask, or expose, the other disc by an extent dependent on the relative positions of rotation.