초록 ▼

The chair includes seat and back assemblies interconnected in a four-bar linkage. The chair further includes a tension mechanism comprising a coil spring projecting forwardly from a base and an adjustment linkage which is connected to said coil spring and to a front link of said four-bar linkage. A

The chair includes seat and back assemblies interconnected in a four-bar linkage. The chair further includes a tension mechanism comprising a coil spring projecting forwardly from a base and an adjustment linkage which is connected to said coil spring and to a front link of said four-bar linkage. A back linkage end of said adjustment linkage being axially movable along an axis of said coil spring and a front linkage end being vertically movable along said front link to adjust displacement of said adjustment linkage during rearward pivoting of said front link.

대표청구항 ▼

What is claimed is: 1. A chair having a seat assembly and a back assembly which are interconnected in a four-bar linkage arrangement, the chair including a base wherein the four-bar linkage arrangement includes a base link fixed to the base and a front link pivotally interconnected to the base link

What is claimed is: 1. A chair having a seat assembly and a back assembly which are interconnected in a four-bar linkage arrangement, the chair including a base wherein the four-bar linkage arrangement includes a base link fixed to the base and a front link pivotally interconnected to the base link and the seat assembly so as to pivot rearwardly upon tilting of said seat and back assemblies, a tension control mechanism including a spring arrangement comprising a coil spring affixed to the base link and an adjustment linkage having a back linkage end connected to a front end of said coil spring and a front linkage end connected to said front link, said back linkage end being slidable axially along the longitudinal axis of said spring and said front linkage end being slidable vertically along said front link wherein the vertical position of said front linkage end on said front link defines the axial displacement of said back end of said adjustment linkage during rearward pivoting of said front link. 2. The chair according to claim 1, wherein said spring arrangement includes an actuator mechanism which displaces said front linkage end along said front linkage. 3. The chair according to claim 2, wherein said actuator mechanism comprises an actuator handle which is manually actuated to vary the position of said front link end. 4. The chair according to claim 1, wherein said coil spring generates a restoring force acting along said adjustment linkage and forwardly on said front link to resist rearward pivoting of said front link. 5. The chair according to claim 4, wherein said coil spring is compressed during rearward pivoting of said front link to generate said restoring force, and the position of said front link varies the amount of compression of said coil spring and thereby varies the amount of restoring force generated during rearward pivoting. 6. A chair having a seat assembly and a back assembly which are interconnected in a linkage arrangement, the chair including a base wherein the linkage arrangement includes a base link fixed to the base and a front link pivotally interconnected to the base link and the seat assembly so as to pivot rearwardly upon tilting of said seat and back assemblies, said linkage arrangement further comprising said back assembly pivotally interconnected with said base link and said seat assembly to effect said rearward pivoting of said front link, a tension control mechanism including a resilient biasing arrangement comprising an adjustable biasing member affixed to the base link and an adjustment linkage having a back linkage end connected to a front end of said adjustable biasing member and a front linkage end connected to said front link such that said adjustable biasing member generates an adjustable restoring force on said front link which resists said rearward pivoting of said front link, said back linkage end being slidable axially along a longitudinal axis of said adjustable biasing member, and said front linkage end being slidable vertically along said front link wherein the vertical position of said front linkage end on said front link defines the axial displacement of said back end of said adjustment linkage during rearward pivoting of said front link to vary the adjustable restoring force generated by said adjustable biasing member. 7. The chair according to claim 6, wherein said adjustable biasing member is a coil spring disposed in compression between said base link and said adjustment linkage during rearward tilting of said seat and back assembly to generate said adjustable restoring force. 8. The chair according to claim 6, wherein said adjustable biasing member is disposed in a fixed orientation relative to said base link, and said adjustment linkage is pivotally connected to said front link and said adjustable biasing member. 9. The chair according to claim 8, wherein said back linkage end moves linearly along the longitudinal axis of said adjustable biasing member during pivoting of said front link. 10. The chair according to claim 6, wherein said tension control mechanism comprises a fixed-load biasing member which generates a fixed restoring force which resists tilting of said seat and back assemblies in addition to said adjustable restoring force. 11. The chair according to claim 10, wherein said fixed-load biasing member and said adjustable biasing member comprising resiliently deflectable springs. 12. The chair according to claim 6, wherein said front link is pivotally connected to said base link at a first pivot connection, wherein the axial displacement of said back end of said adjustment linkage is increased upon movement of the front linkage end away from said first pivot connection.