Height-adjusting mechanism for chair seat

In a chair having a seat means, a base having thereon an upwardly-projecting pedestal defining a central opening which projects vertically downwardly therethrough, a vertically-elongated spindle having the upper end portion thereof nonrotatably secured to said seat means, said spindle projecting downwardly so that the lower portion thereof is rotatably positioned and confined within said central opening, said spindle having an elongated central portion thereof provided with external threads, and a load-released height-adjusting mechanism coacting between said spindle and said pedestal for (1) rotatably supporting the seat means when occupied for rotation about the axis of the spindle and (2) permitting the height of said seat means when unoccupied to be vertically adjusted responsive to rotation of the unoccupied seat means relative to the base, said height-adjusting means including a nut threadably engaged with said spindle, a first clutch means for nonrotatably connecting said nut to said spindle when said seat means is occupied, a second clutch means for nonrotatably connecting said nut to said pedestal when said seat means is unoccupied, and spring means normally urging said nut upwardly relative to said pedestal for effecting engagement of said second clutch means when the seat means is unoccupied, the improvement comprising:

• an enlarged bore formed in said pedestal and projecting downwardly from the upper end thereof in concentric relationship to said central opening, said second clutch means being mounted adjacent the upper end of said pedestal, said first clutch means being positioned within said bore downwardly a substantial distance below said second clutch means, said nut being disposed vertically between said first and second clutch means, said second clutch means includinng a second clutch element fixed to said pedestal adjacent the upper end thereof and disposed for engagement with an opposed upper clutch portion formed on the upper end of said nut when said nut is in a raised position due to said seat means being unoccupied, said first clutch means including a first clutch element which is axially seated on a shoulder formed on said pedestal in axially downwardly spaced relationship from the upper end of said pedestal, said first clutch element being nonrotatably but axially slidably connected to said spindle and being engageable with an opposed lower clutch portion formed on the lower end of said nut when the latter is in its lower position due to said seat means being occupied, and said spring means comprising a coil spring concentrically disposed within said bore and having the lower end thereof seated on said pedestal and the upper end thereof disposed in operative engagement with said nut for continuously urging the latter upwardly toward said second clutch element, said coil spring being disposed in encircling relationship to said first clutch element, whereby said nut is totally disengaged and is spaced axially upwardly from said first clutch element when in said upper position.