Office chairs

• US 4,408,800 A
• Filed: 06/11/1980
• Issued: 10/11/1983
• Est. Priority Date: 06/11/1980
• Status: Expired due to Term

• Current Assignee: Unisys Corporation
• Original Assignee: American Seating Company
• Inventors: Knapp, Robert L.
• Primary Examiner(s): McCall, James T.
• Application Number:
  US06/158,433
• Time in Patent Office: 1,217 Days
• Field of Search: 297/285, 297/300, 297/301, 297/307, 297/347, 297/71, 297/306, 297/361, 297/358, 251/77, 251/233, 251/251, 251/254, 137/636.1, 248/631
• US Class Current: 297/301.2
• CPC Class Codes: A47C 1/0244 by fluid means
• CPC Class Codes: A47C 1/03283 with fluid springs
• CPC Class Codes: A47C 3/30 with vertically-acting fluid cylinder

Abstract

Improvements for office chairs are described which include a cam control mechanism having two operative positions under control of the occupant. In the first position the cam actuates a first pneumatic cylinder to adjust the height of the seat over a continuous range. In the second position, the cam independently actuates a second pneumatic cylinder for adjusting the postural attitude of the backrest over a continuous range about a pivot located at the sacral level of the occupant. In the postural adjustment mode, the cam may be positioned to actuate the backrest adjusting cylinder continuously so that the backrest provides a floating support or dynamic cushioning to the back of the occupant. The backrest cushion assembly is mounted to its support by means of a pair of laterally spaced cushion mounts which provide lesser resistance and support to body motions in a fore-and-aft plane but greater support to laterally backward motion, as when the occupant is reaching for something.

Claims

1. In an office chair comprising a base adapted to support the chair;

seating means including a seat support frame above said base; and

a backrest assembly for supporting the back of an occupant of said chair and pivotally mounted to said seat support frame for rotation about a horizontal axis, the improvement comprising;

first pneumatic cylinder means interconnecting said seat support frame with said base of said chair for adjusting the height of said seat support frame and including a first actuator valve;

second pneumatic cylinder means interconnected between said backrest assembly and said seat support frame for adjusting said backrest in postural attitude and including a second actuator valve; and

an actuating mechanism carried by said seat support frame for selectively independently actuating said first and second pneumatic cylinder means and including a cam member mounted in said seat support frame for rotation about a horizontal axis transverse of said chair, a rotatable shaft connected to said cam and journalled in said frame and accessible by said occupant, said cam member having first and second cam surfaces for selectively engaging and actuating said first and second actuator valves of said first and second pneumatic cylinder means respectively when said shaft is rotated respectively in a first angular direction and a second angular direction counter to said first angular direction.

2. The apparatus of claim 1 wherein said cam shaft has a neutral position in which said cam does not actuate either of said valve actuators;

and one of said cam surfaces further comprises means for coupling to said valve actuator of said second pneumatic cylinder means in a stable position, whereby said second pneumatic cylinder means remains unlocked and said cam is prevented from returning to said neutral position, and said backrest provides dynamic cushioning for said occupant.

3. The apparatus of claim 2 wherein said coupling means comprises a recess in said cam located such that when said cam shaft is rotated in said counter direction, said second cam surface actuates said second pneumatic cylinder means first and then as said shaft is rotated still further in said counter direction, said recess couples to said valve actuator of said second pneumatic cylinder means in stable relation.

4. In an office chair having a base;

seat means supported by said base and a backrest assembly including a backrest support mounted to said seat means and a backrest means, an improved mounting for said backrest means comprising;

first and second cushion mounts for mounting said backrest means to said backrest support, each cushion mount including

a body of flexible resilient material and having an axis, said axes of said bodies extending generally vertically and separated laterally relative to said chair,

a pair of studs located generally axially of said body and each stud having first and second ends, said first ends extending outwardly of said body in general vertical directions, and said second ends being spaced from one another and attached to said body; and

means for securing said first ends of each pair of studs respectively to said backrest support and said backrest means, whereby said bodies are placed in a bending mode of deflection when said backrest means is tilted about a horizontal axis to offer a lesser resistance, and said bodies are placed in shear when said backrest means is rotated about a vertical axis to offer greater resistance to displacement.

5. The apparatus of claim 4 wherein said backrest support includes a first upper horizontal flange and said securing means further includes a second horizontal flange secured to said backrest means and spaced above and extending parallel to said first flange;

said first ends of each pair of studs being externally threaded and extending through associated ones of said flanges; and

nuts for securing said studs to said associated flanges.

6. The apparatus of claim 4 further comprising means for limiting positively the amount said backrest means may be rotated about a horizontal axis while not limiting its rotation about a vertical axis.

7. An office chair comprising a base adapted to support the chair;

seating means including a seat support frame above said base;

a backrest assembly for supporting the back of an occupant of said chair and including a support member;

means for pivotally attaching said backrest support member to said seat support frame behind the sacral area of an occupant of said chair;

first pneumatic cylinder means interconnecting said seat support frame with said base of said chair for adjusting the height of said seat support frame;

second pneumatic cylinder means interconnected between said backrest support member and said seat support frame for adjusting said backrest in postural attitude; and

an actuating mechanism carried by said seat support frame for selectively independently actuating said first and second pneumatic cylinder means and including a cam member mounted in said seat support frame for rotation about a horizontal axis transverse of said chair, a rotatable shaft connected to said cam and journalled in said frame and accessible by said occupant, said cam member having a first cam surface for selectively engaging and actuating said first pneumatic cylinder means when said shaft is rotated in a first angular direction and a second cam surface for engaging and actuating said second pneumatic cylinder means when said shaft is rotated in a second angular direction counter to said first angular direction; and

means for securing the rod end of said second pneumatic cylinder means to said backrest support member comprising an anchor block with an internally threaded bore slidably received in said seat support frame, said seat support frame defining vertically extending slots to receive said anchor block while preventing fore-and-aft motion thereof, the rod of said second pneumatic cylinder means defining external threads received in said internally threaded bore of said anchor block.

8. An office chair comprising:

a base adapted to support the chair;

seating means including a seat support frame above said base;

a backrest assembly for supporting the back of an occupant of said chair and including a backrest support member carrying a backrest and defining a first horizontal flange, means defining a second horizontal flange, means for pivotally connecting said backrest support member to said seat support frame, and first and second cushion mount means interconnecting said first and second horizontal flanges, each cushion mounting means comprising a resilient member defining a generally vertical axis, each of said cushion mount means further including upper and lower studs integrally embedded in each of said cushion members and generally axially aligned with said cushion member and with each other when said cushion members are not being deflected;

means for attaching the downwardly extending studs of said cushion mount means to one of said horizontal flanges; and

second means for securing the upwardly extending stud members of said cushion mount means to the other of said horizontal flanges;

said axes of said resilient members being laterally spaced relative to each other and each resilient member being characterized as being deflected in a bending mode transverse of said axis when said back is rotated about a horizontal axis in a fore-and-aft direction to offer a lesser resistance to displacement, and being deflected in a shear mode when said backrest assembly is twisted about a vertical axis to offer a greater resistance to displacement;

means for positively limiting the rotation of said backrest relative to said backrest support member;

first pneumatic cylinder means interconnecting said seat support frame with said base of said chair for adjusting the height of said seat support frame and including a first actuator valve;

second pneumatic cylinder means interconnected between said backrest assembly and said seat support frame for adjusting said backrest in postural attitude; and

an actuating mechanism carried by said seat support frame for selectively independently actuating said first and second pneumatic cylinder means and including a cam member mounted in said seat support frame for rotation about a horizontal axis transverse of said chair, a rotatable shaft connected to said cam and journalled in said frame and accessible by said occupant, said cam member having a first cam surface for selectively engaging and actuating said first pneumatic cylinder means when said shaft is rotated in a first angular direction and a second cam surface for engaging and actuating said second pneumatic cylinder means when said shaft is rotated in a second angular direction counter to said first angular direction.