Chair control for a pedestal chair having a knee-tilt seat

• US 4,906,045 A
• Filed: 03/20/1989
• Issued: 03/06/1990
• Est. Priority Date: 03/20/1989
• Status: Expired due to Fees

• Current Assignee: Knoll Incorporated (Millerknoll Incorporated)
• Original Assignee: The Shaw-Walker Company
• Inventors: Hofman, William K.
• Primary Examiner(s): NOT, DEFINED
• Application Number:
  US07/325,539
• Time in Patent Office: 351 Days
• Field of Search: 297/304, 297/300, 248/609, 248/608
• US Class Current: 297/303.3
• CPC Class Codes: A47C 3/026 with central column, e.g. rocking office chairs; Tilting chairs
• CPC Class Codes: A47C 7/441 with adjustable elasticity
• CPC Class Codes: A47C 7/448 with resilient blocks

Abstract

A chair control for a pedestal chair having a knee-tilt seat. An elastomeric torsion spring is offset rearwardly from the tilting axis of the seat. The seat and torsion spring are operatively connected by a cam surface and a cam follower which effectively reduce the restoring force exerted by the torsion spring against the seat as the rearward tilt of the seat increases. A mechanism to adjust the initial restoring torque of the torsion spring provides a large angular twist of the torsion spring with a minimum linear movement of the mechanism. The chair control provides the chair seat with a less than conventional seat angle relative to the horizontal when the chair is unoccupied. A mechanism is provided to enable the occupant to adjust the chair seat to a more conventional seat angle in its unoccupied condition.

Claims

1. A chair control for a pedestal chair having a knee-tilt seat, a chair post tube and a housing extending between said knee-tilt seat and said chair post tube, said chair control including:

a seat support pivot member pivotally mounted on said housing for rotation about a generally horizontal axis located forward of said chair post tube,

means mounted on said seat support pivot member for supporting said seat,

a torsion spring means mounted on said housing rearwardly of said seat support pivot member for rotation about a generally horizontal axis,

cam follower means and an arm having cam surface means, one of said means and said arm attached to one of said seat support pivot means and said torsion spring means, with said cam surface means engaging said cam follower means to bias said seat support pivot member to tilt said seat forwardly,

one of said arms having cam surface means and cam follower means extending non-axially relative to the horizontal axis of rotation of its means,

the engagement between said cam follower means and said cam surface means moving farther away from the horizontal axis of rotation of its means as said support pivot member rotates from its unoccupied position to its fully rearwardly-tilted position to thereby effectively decrease the force exerted by said torsion spring means against said seat support pivot member.

2. The chair control of claim 1 including means to adjust the amount of torque initially exerted by said torsion spring means against said seat support pivot member.

3. The chair control of claim 1 in which said cam follower means is a roller.

4. The chair control of claim 1 in which said torsion spring means is a tubular elastomeric spring.

5. The chair control of claim 4 in which the cam surface arm is affixed to an inner surface of the tubular elastomeric spring.

6. The chair control mechanism of claim 1 further including means to selectively prevent the seat support pivot member from rotating the seat to its maximum forwardly tilt position.

7. The chair control mechanism of claim 6 in which said means to selectively prevent the seat support pivot member from rotating the seat to its maximum forwardly tilt position includes a stop member which engages said cam follower means, said stop member having a block formed thereon, and means to rotate said stop member to move said block into and out of engagement with said cam follower means to restrict forward rotation of said seat support pivot member when said block engages said cam follower means.

8. The chair control of claim 2 in which said means to adjust the amount of torque initially exerted by said torsion spring means against said seat support pivot member includes a lever affixed to said torsion spring means, a straight cam surface formed on said lever, a cam follower roller mounted for linear movement along a path toward and away from said torsion spring means and which intersects the straight cam surface at an acute angle, which angle decreases as the roller moves away from the torsion spring means, and means to move said cam follower roller along said linear path to increase or decrease the amount of torque initially exerted by the torsion spring means.

9. A chair control mechanism for a pedestal chair having a knee-tilt seat, said control including:

means to tilt said chair rearwardly about a generally horizontal axis located near the front of the seat,

an elastomeric torsion spring means located rearwardly of said generally horizontal axis,

said torsion spring exerting a linearly increasing return torque as it is twisted, and

cam and cam follower means associated with said seat tilt means and said elastomeric torsion spring means to reduce the return torque applied by the torsion spring means against the seat tilt means to less than the linearly increasing rate of the spring means as the seat is tilted to its fully rearwardly-tilted position.

10. A mechanism for adjusting the torque initially exerted by a chair control torsion spring means, including:

a lever affixed to said torsion spring means and adapted to twist said spring means and increase the torque applied by said spring means upon movement of said lever,

a straight cam surface formed on said lever,

a cam follower roller mounted for linear movement along a path toward and away from said torsion spring means, said path intersecting said straight cam surface at an acute angle, which angle decreases as the roller moves away from the torsion spring means along said path, and

means to move said cam follower roller along said linear path to increase or decrease the torque initially exerted by said torsion spring means.

11. The mechanism of claim 10 in which said torsion spring means is an elastomeric spring.