Patent ID: 7044023

Claim:
A knob adjustment device for adjusting the temperature in valve units for water-heating apparatus, the valve units having a rotatable knob and an operating member, the device comprising: a geared transmission interposed between the knob and the operating member of the valve unit in order to transmit a rotary movement to the operating member about a first axis as a result of a rotation of the knob, the geared transmission including a reduction mechanism with a variable transmission ratio such that, for a first and a second angular portion of the rotation of the knob, the operating member is rotated with respective and different first and second transmission ratios (T 1 , T 2 ), the reduction mechanism including (i) a pinion fixed for rotation with the operating member, (ii) a pair of crown wheel sectors having face teeth, coaxial with and fixed for rotation with the knob, the crown wheel sectors being concentrically extended, with respective different diameters and respective, circumferentially spaced apart ends, and being able to mesh with the pinion, and (iii) at least one intermediate tooth radially disposed in a position between the crown wheel sectors and circumferentially disposed in a position between the spaced apart crown wheel sector ends, and able to mesh with the pinion.