Height-Adjusting Assembly for Office Chair Backrest

Abstract

A height-adjusting assembly for an office chair backrest includes a supporting unit mounted with a vertically movable backrest. The supporting unit and the backrest have correspondingly an engaging element and a series of positioning teeth, respectively, to be coupled mutually. Upper and lower ends of the series of positioning teeth have a retracting portion and an expanding portion for retracting and expanding the engaging element, respectively. When the backrest slides upward, the engaging element successively engages with one of the positioning teeth so as to position the backrest at a desired height. When the backrest reaches to an upmost position, the engaging element is pressed by the retracting portion and retracts so as to separate from the positioning teeth. Then the backrest reaches a bottommost position thereof has the engaging element expanded by the expanding portion, thereby allowing the engaging element to engage with the positioning teeth again.

1 . A height-adjusting assembly for an office chair backrest, comprising a supporting unit fixed to a chair for allowing a backrest to be mounted thereon, therein:
 the supporting unit being a frame provided with at least one series of positioning teeth, wherein an upper end and a lower end of the series of positioning teeth are provide with a retracting portion and an expanding portion, respectively;   the backrest having at least one sliding portion corresponding to the series of positioning teeth of the supporting unit, and an engaging element pivotally fixed thereto for resiliently coupling with any of the positioning teeth, wherein the engaging element and the sliding portion have correspondingly a socket portion and a plug portion to be coupled with each other while the retracting portion and the expanding portion of the supporting unit serve to retract and expand the engaging element, respectively, so as to make the socket portion and the plug portion engaged or separated.   
     
     
         2 . The height-adjusting assembly of  claim 1 , wherein the sliding portion on the supporting unit includes a recessed part formed on the backrest and a cover, which such covers the recessed part that a space is defined between the recessed part and the cover for allowing the supporting unit to pass therethrough. 
     
     
         3 . The height-adjusting assembly of  claim 1 , wherein a waist-rest portion is pivotally attached below the backrest for providing resilient support.