Office chairs

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.

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.

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.