Tilt control for chair

• US 20010000939A1
• Filed: 12/21/2000
• Published: 05/10/2001
• Est. Priority Date: 04/30/1997
• Status: Active Grant

• Current Assignee: Haworth Incorporated
• Original Assignee: Haworth Incorporated
• Inventors: Clark, John, Simpson, Steve, Nelson, Patrick, Dral, Joel, Wilkerson, Larry Allen, Roark, Troy, Roslund, Richard N. Jr.
• Granted Patent: US 6,361,110 B2
• Time in Patent Office: Days
• US Class Current: 297/303.3
• CPC Class Codes: A47C 1/03255 with a central column, e.g. rocking office chairs
• CPC Class Codes: A47C 1/03266 with adjustable elasticity
• CPC Class Codes: A47C 1/03272 with coil springs

Abstract

A tilt control mechanism for an office chair includes a spring arrangement which permits forward and rearward tilting of the chair while also urging the chair to a normal upright position. The spring arrangement includes front and rear springs which act in combination such that the upward acting forces acting on the chair can be varied during use. The forces being applied by the front spring are adjusted by a side-actuated tension adjustment mechanism which incorporates a wedge block for adjusting the spring forces. Further, the rear springs provide a variable spring force such that the spring force is maximized when in the normal position but is decreased substantially once the chair is fully reclined. This reduction in spring force allows a user to maintain the chair in the fully reclined position with significantly less force than was required to tilt the chair rearwardly while a sufficient spring force continues to be applied by the front spring to urge the chair to the normal position.

Claims

1. In a chair having a base, a seat assembly, a back assembly and a tilt control mechanism which is supported on said base and effects rearward tilting of said seat and back assemblies in response to a user, said tilt control mechanism including a fixed body supported on said base and a pivot member which pivots downwardly relative to said fixed body about a sidewardly extending horizontal pivot axis in response to said rearward tilting of said seat and back assemblies, said tilt control mechanism further including a spring having a first leg portion acting on said fixed body and a second leg portion acting on said pivot member, said second leg portion being resiliently deflectable relative to said first leg portion so as to act against but permit pivoting of said pivot member about said pivot axis and bias said pivot member to counteract said rearward titling of said seat and back assemblies, the improvement comprising an adjustment mechanism for adjusting a deflection of said first leg portion relative to said second leg portion, said adjustment mechanism including a tension adjustment handle which is movable sidewardly relative to said fixed body, and a wedge which is slidable toward and away from said spring in an axial direction transverse to the movement of said adjustment handle, said adjustment mechanism further including connector means for transferring said sideward movement of said adjustment rod into said axial movement of said wedge to move one of said first and second leg portions vertically to vary the spring force being applied by said spring on said pivot member.

2. A chair according to

claim 1

, wherein said connector means comprise an elongate track which projects upwardly from said fixed body and is oriented at an angle relative to said pivot axis, said wedge including an elongate channel which opens from a bottom surface thereof and slidably receives said track therein, said wedge being slidable along said track so as to have both a forward component of motion and a sideward component of motion.

3. A chair according to

claim 2

, wherein said adjustment rod is threadingly engaged with said fixed body such that rotation of said adjustment rod effects sideward movement thereof, said rod acting against a side surface of said wedge and being movable toward said wedge so as to effect said angled sliding of said wedge along said track toward said spring.

4. A chair according to

claim 3

, wherein said wedge includes an inclined surface facing toward said spring, said one of said first and second leg portions being slidable axially along said inclined surface as said wedge is moved axially to effect vertical movement of said one of said first and second leg portions.

5. A chair according to

claim 1

, wherein said first leg portion acts downwardly on a bottom surface of said fixed body, and said second leg portion acts upwardly on said pivot member.

6. A chair according to

claim 1

, wherein a plate is positioned between an inclined surface of said wedge and said one of said first and second leg portions being moved by said wedge, said plate including mounting means for mounting said plate on said fixed body so as to be movable vertically by said wedge to effect a corresponding vertical movement of said one of said first and second leg portions, said mounting means limiting sideward movement of said plate to thereby prevent sideward movement of said one of said first and second leg portions in response to said sideward component of motion of said wedge.

7. In a chair having a base, a seat assembly, a back assembly and a tilt control mechanism which is supported on said base and effects rearward tilting of said seat and back assemblies in response to a user, said tilt control mechanism including a fixed body supported on said base and a pivot member which pivots downwardly relative to said fixed body about a sidewardly extending horizontal first pivot axis in response to said rearward tilting of said seat and back assemblies, said tilt control mechanism further including a spring having a first leg portion acting on said fixed body and a second leg portion acting on said pivot member, said second leg portion being resiliently deflectable relative to said first leg portion so as to act against but permit pivoting of said pivot member about said first pivot axis and bias said pivot member to counteract said rearward titling of said seat and back assemblies, the improvement comprising adjustment means for adjusting an effective spring rate of said spring, said adjustment means comprising an arcuate bearing surface supported on said fixed body, an end of said first leg portion acting downwardly on a top surface portion of the arcuate bearing surface so as to act with a vertical force component thereon, said spring being movable downwardly with said pivot member such that said first leg portion is deflected upwardly to increase a spring force acting on the pivot member, said first leg portion being inclined so as to act axially and downwardly on a side of said bearing surface such that said spring force includes horizontal and vertical force components.

8. A chair according to

claim 7

wherein said arcuate bearing surface is supported on a rearward end of said fixed body, said spring being movable downwardly so that said first leg portion extends axially and upwardly toward said arcuate bearing surface into contact with said side thereof.

9. A chair according to

claim 7

, wherein said tilt control mechanism includes a back support member which has a forward end pivotally connected to said fixed body and a rearward end which supports said back assembly, a rearward end of said pivot member being pivotally connected to said back support member rearwardly of said second pivot axis such that said back support member moves downwardly in combination with said pivot member, said spring being supported on said back support member so as to move vertically therewith.

10. A chair according to

claim 7

, which includes a second spring having a first leg portion acting on said fixed body and a second leg portion acting on said pivot member, said second leg portion being resiliently deflectable relative to said first leg portion so as to act against but permit pivoting of said pivot member about said first pivot axis and bias said pivot member to counteract said rearward tilting of said seat and back assemblies, said second spring providing a substantially continuous spring force which acts on said pivot member during pivoting thereof.

11. A chair according to

claim 10

, which includes adjustment means for adjusting said spring force being provided by said second spring.

12. A chair according to

claim 11

, wherein said adjustment means comprises a wedge which is slidable in an axial direction toward and away from one of said first and second leg portions of said second spring, and actuation means for moving said wedge in said axial direction toward said spring to deflect one of said first and second leg portions thereof relative to the other of said first and second leg portions to adjust the spring force provided thereby.

13. A chair comprising:

a seat assembly for supporting a seat of a user;

a back assembly for supporting a back of a user;

a base; and

a tilt control mechanism which is supported on said base and effects rearward tilting of said seat and back assemblies in response to a user, said tilt control mechanism including a fixed body supported on said base, a back support member which projects rearwardly away from said fixed body and includes a forward end pivotally connected to said fixed body such that said back support member pivots vertically about a first horizontal pivot axis, and a top plate overlying said fixed body which includes a front portion which is pivotally connected to said fixed body so as to pivot vertically about a second horizontal pivot axis and a rear portion which is connected to said back support member such that said top plate and said back support member pivot vertically together in response to said rearward tilting of said seat and back assemblies, said seat assembly being supported on said top plate and said back assembly being supported on said back support member, said tilt control mechanism further including a front spring and a rear spring biasing said top plate upwardly, said front spring having a first leg acting on said fixed body and a second leg acting upwardly on said top plate, said first and second legs of said front spring being resiliently deflectable relative to each other such that said second leg acts against but permits pivoting of said top plate about said second pivot axis and biases said top plate to counteract said rearward tilting of said seat and back assemblies, said second spring being supported on said back support member so as to move vertically therewith and including a lower leg acting downwardly on a rear portion of said fixed body and an upper leg acting upwardly on said top plate, said first and second legs of said second spring being resiliently deflectable relative to each other so as to act against but permit pivoting of said pivot member about said first pivot axis and bias said pivot member to counteract said rearward tilting of said seat and back assemblies, said rear portion of said fixed body including an upward facing arcuate bearing surface which supports an end of said lower leg of said rear spring thereon, said lower leg extending forwardly so as to act on a top surface portion of the bearing surface to act with a vertical force component, said lower leg extending upwardly from said second spring as said second spring is moved vertically downwards by said back support member such that said lower leg acts on a side of said bearing surface with both horizontal and vertical force components.

14. A chair according to

claim 13

, wherein said tilt control mechanism includes adjustment means for adjusting said spring force provided by said front spring, said spring force being applied by said front spring acting substantially continuously during downward pivoting of said top plate.

15. A chair according to

claim 14

, wherein one of said first and second spring legs of said front spring are deflected vertically by said adjustment means so as to increase and decrease said spring force.

16. A chair according to

claim 13

, wherein a plastic spacer is provided between said upper leg of said rear spring and a downward facing surface of said top plate so as to limit friction therebetween.

17. A chair according to

claim 16

, wherein said front and rear springs are coil springs, said rear spring being supported on said back support member by a cylindrical body inserted in a hollow interior of said rear spring, said elastic member being formed integrally with said cylindrical body and projecting forwardly therefrom.