Chair waist backrest height adjusting device
A chair waist backrest height adjusting device includes a chair backrest bracket above the backrest, a worm rotated by turning the adjusting rod to slightly lower position, a first gear that is engaged with it and a second gear that is coaxially rotated with the first gear, and the chair backrest bracket under the backrest is provided with a waist backrest that can be slid up and down. The back of the waist backrest is provided with a tooth-row that is engaged with the second gear, so that the seated person on the chair can stretch out one or two hands to the adjustment rod for the forward or reverse turning operation, and the waist backrest can easily drive the waist backrest up and down, further the waist backrest is more easily adjusted, and there will be no displacement in the adjusted waist backrest.
1. A chair waist backrest height adjusting device comprising:
a chair backrest bracket, a waist backrest, and a backrest disposed above the chair backrest bracket,
wherein the waist backrest is configured to be slid up and down the chair backrest bracket,
wherein a longitudinal tooth-row is disposed on the back of the waist backrest;
wherein the chair backrest bracket has a first gear and a second gear, wherein the second gear is engaged with the longitudinal tooth-row disposed on the back of the waist backrest, and the first gear is coaxially disposed with the second gear and rotated synchronously;
wherein a holding slot with a supporting shaft is recessed on the chair backrest bracket, so that the first gear shaft and second gear shaft are fixed on the supporting shaft;
wherein the chair backrest bracket has an adjusting rod inserted into the holding slot, and
wherein the adjusting rod is fixed with a worm engaged with the first gear in the holding slot, such that rotation of the adjusting rod causes the waist backrest to be adjusted up and down by the first gear, the second gear and the tooth-row.