Knob with different gear ratios
A knob adjustment device particularly for adjusting the temperature in valve units for water-heating apparatus. The device comprises a geared transmission interposed between the knob and an operating member of the valve unit in order to transmit a rotary movement to the member about its own axis as a result of a rotation of the knob. The geared transmission includes a reduction mechanism with a variable transmission ratio such that, for a first angular portion and a second angular portion of the rotation of the knob, the member is rotated with respective different transmission ratios (T 1 ,T 2 ).
1. 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.
2. 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, substantially as extensions of one another with respective different diameters, 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 able to mesh with the pinion, the crown wheel sectors and the at least one intermediate tooth are spaced apart circumferentially in a manner such that the pinion meshes alternatively with one or the other of the respective crown wheel sectors or with the at least one intermediate tooth.
3. The device according to claim 1 , in which the at least one intermediate tooth extends concentrically with the crown wheel sectors along an arc with a diameter having an intermediate value between the diameters of the crown wheel sectors.
4. The device according to claim 1 , in which the crown wheel sectors and the at least one intermediate tooth have a circumferential extent such that the operating member is rotated for a first angular portion and a second angular portion corresponding with the respective first and second transmission ratios (T 1 ,T 2 ), the first transmission ratio (T 1 ) between the first crown wheel sector and the pinion being approximately three times the second transmission ratio (T 2 ) between the second sector and the pinion.
5. The device according to claim 4 , in which the transmission ratio between the intermediate tooth and the pinion is an intermediate ratio (T 3 ) between the first and second transmission ratios (T 1 ,T 2 ) of the crown wheel sectors.
6. The device according to claim 2 , in which the at least one intermediate tooth extends concentrically with the crown wheel sectors along an arc with a diameter having an intermediate value between the diameters of the crown wheel sectors.
7. The device according to claim 2 , in which the crown wheel sectors and the at least one intermediate tooth have a circumferential extent such that the operating member is rotated for a first angular portion and a second angular portion corresponding with the respective first and second transmission ratios (T 1 ,T 2 ), the first transmission ratio (T 1 ) between the first crown wheel sector and the pinion being approximately three times the second transmission ratio (T 2 ) between the second sector and the pinion.
8. The device according to claim 7 , in which the transmission ratio between the intermediate tooth and the pinion is an intermediate ratio (T 3 ) between the first and second transmission ratios (T 1 ,T 2 ) of the crown wheel sectors.