Patent ID: 7387343

Claim:
A constricting device which is secured to a footrest ring of a chair, comprising: a constricting unit, said constricting unit being assembled between a conical sleeve of said footrest ring and a center tube of said chair, said sleeve of said footrest ring being a cone-shaped body to be fitted with said center tube of said chair, said constricting unit composed of a constricting main body and a fixing ring, said fixing ring having an upper edge extending outwardly to form a stop flange; said constricting main body being conically shaped and fitted in said conical sleeve of said footrest ring, said fixing ring being engaged with an upper end of said constricting main body, said stop flange being greater in diameter than said sleeve of said footrest ring and contacting an upper end thereof to thereby secure said constricting main body within said sleeve of said footrest ring, said constricting main body having a centrally disposed fitting through bore to be fitted around said center tube of said chair, said constricting main body having its circumferential wall cut with a plurality of axial grooves spaced apart equidistantly; and said fitting through bore of said constricting main body having an inner wall annularly provided with a plurality of recesses, each recess having a wall with an insert hole formed therethrough, said constricting main body being further provided with a plurality of non-slip pads, each of said non-slip pads having an upper edge formed with a projecting block, said non-slip pads being respectively positioned in said recesses, said projecting blocks of non-slip pads being respectively inserted in said insert holes.