Back position control device for chairs

• US 4,062,587 A
• Filed: 01/13/1976
• Issued: 12/13/1977
• Est. Priority Date: 01/13/1976
• Status: Expired due to Term

• Current Assignee: Herman Miller Incorporated
• Original Assignee: Herman Miller Incorporated
• Inventors: Wolters, Richard H.
• Primary Examiner(s): Frazier, Roy D.
• Assistant Examiner(s): Lyddane, William E.
• Application Number:
  US05/648,794
• Time in Patent Office: 700 Days
• Field of Search: 297/300, 297/304-306, 297/326, 297/354, 297/355, 297/373, 297/374, 403/111, 248/293, 16/140, 16/180
• US Class Current: 297/302.3
• CPC Class Codes: A47C 1/027 by means of clamps or friction locking members

Abstract

A pivotally mounted back support for a chair is disclosed incorporating a pivotal mounting utilizing a plurality of interleaved clutch plates. Alternate ones of the clutch plates are stationary and the remainder are connected to the lower end of the back support post to pivot with the post about a common pivot shaft. Locking of the fore and aft pivotal position of the back is effected by squeezing together the clutch plates to provide a surface-to-surface frictional bond. Springs urge the post into erected position. A handle, readily accessible to a person seated on the chair is provided to effect locking and release of the clutch and thus pivotal adjustment of the position of the back.

Claims

1. In a chair having a seat supporting plate and a back supporting post, a manually operable clutch pivotally mounting said post to the rear portion of said plate, said clutch comprising:

a trunnion having a pair of laterally spaced side members, said trunnion rigidly mounted to said plate and projecting rearwardly therefrom;

said arms having a pair of aligned apertures;

said post having a pair of elongated spaced wings rigidly secured to the lower end thereof received between said side members and extending forwardly at an acute angle to said post toward said plate;

a shaft extending through said apertures and said wings adjacent the bottom of said post;

means including annular bushings supporting said shaft in said apertures whereby it serves as the pivotal support for said post;

spring means engaging the forward end of said wings and said plate and the lower end of said post forward of said shaft and pivotally urging said forward end of said wings downwardly and said post into forwardly erected position;

at least one elongated clutch plate slidably mounted on said shaft between each of said wings and the adjacent one of said side members;

means secured against movement with respect to said supporting plate and attached to each of said clutch plates and holding said clutch plates against rotation about said shaft;

a handle mounted on one end and a stop mounted on the other end of said shaft, said handle being rotatable for changing the spacing between said stop and said handle for forcing said clutch plates into tight frictional engagement with said wings locking said post against pivotal movement.

2. The chair described in claim 1 wherein a first plurality of said clutch plates are provided adjacent each of said wings, a second plurality of clutch plates of similar construction adjacent each of said wings, said clutch plates of said second plurality being alternately positioned between the clutch plates of said first plurality;

said spring means engaging the forward ends of said second plurality of clutch plates whereby said second plurality of clutch plates will rotate with said wings.

3. The chair described in claim 2 wherein a pin is provided, said pin engaging said spring means and all of said second plurality of clutch plates.

4. The chair described in claim 3 wherein said holding means is a pin attached to all of said first plurality of clutch plates and a pair of fixed stops, one engaging said pin and the other engaging said plates, said stops acting in opposite directions.

5. The chair described in claim 1 wherein means are provided for holding said shaft against rotation, said handle being threadedly mounted on said shaft.

6. In a chair having a seat supporting plate and a back supporting post, a manually operable clutch pivotally mounting said post to the rear portion of said plate, said clutch comprising:

a trunnion having a pair of laterally spaced side members, said trunnion rigidly mounted to said plate and projecting rearwardly therefrom;

said arms having a pair of aligned apertures;

said post having a pair of elongated spaced wings rigidly secured to the lower end thereof received between said side members and extending at an acute angle to said post toward said plate;

a shaft extending through said apertures and said wings adjacent the bottom of said post;

means including annular bushings supporting said shaft in said apertures whereby it serves as the pivotal support for said post;

spring means engaging the forward end of said wings and pivotally urging said post into forwardly erected position;

a plurality of clutch plates mounted on said shaft between each of said wings and the adjacent one of said side members and axially slidable along said shaft;

said clutch plates being divided into first and second groups with those of the first group being positioned alternately with respect to those of the second group;

means holding the clutch plates of said first group against rotation about said shaft;

means interconnecting said clutch plates of said second group to said wings for rotation therewith about said shaft;

a handle mounted on one end and a stop mounted on the other end of said shaft, said handle being rotatable for changing the spacing between said stop and said handle for forcing said clutch plates into tight frictional engagement with each other and said wings locking said post against pivotal movement.

7. The chair as described in claim 6 wherein said interconnecting means is a pin secured to said forward end of said wings;

said spring being wrapped around said pin and having one end engaging said post and the other end engaging said plate and urging said pin downwardly;

a limit member on said trunnion for restricting the downward movement of said pin.

8. The chair described in claim 7 wherein a wear plate is mounted on the rear surface of said support plate, said wear plate having a central channel for slidably engaging said other end of said spring.

9. The chair described in claim 8 wherein said wear plate is of a plastic material to silence the movement of said spring.

10. The chair described in claim 8 wherein the upper end of said wear plate projects rearwardly and serves as that portion of said holding means resisting downward pivotal movement of said clutch plates of said one group of clutch plates.

11. The chair described in claim 10 wherein a bar is secured to said side members and serves as that portion of said holding means restricting upward pivotal movement of said clutch plates of said one group of clutch plates.

12. In a chair having a seat supporting plate and a back supporting post, means pivotally mounting said post to the rear portion of said plate, said means comprising:

a trunnion having a pair of laterally spaced side members, said trunnion rigidly mounted to said plate and projecting rearwardly therefrom;

the lower end of said post received between said side members and having a foot portion extending forwardly at an acute angle to said post toward said plate;

a shaft pivotally mounting said post at a point adjacent the juncture of said post and foot portion to said side members;

a pin at the forward end of said foot portion;

spring means wrapped around said pin and having one end engaging the bottom of said foot portion and the other end engaging said plate and urging said pin downwardly and said post into erected position;

a limit member on said trunnion for restricting the downward movement of said pins and foot portion, said spring being formed into an inverted V when said post is pivoted rearwardly;

a handle element mounted on one end of said shaft and rotatable for forming a tight frictional lock between said foot portion and said side members.

13. A chair as described in claim 12 wherein a wear plate is mounted on the rear face of said plate;

said wear plate having a rearwardly opening channel slidably receiving said other end of said spring;

said wear plate being of a non-metallic, wear resistant material for silencing the operation of said spring.

14. In a chair having a seat supporting plate and a back supporting post, a manually operable clutch pivotally mounting said post to the rear portion of said plate, said clutch comprising:

a trunnion having a pair of laterally spaced side members, said trunnion rigidly mounted to said plate and projecting rearwardly therefrom;

said arms having a pair of aligned apertures;

said post having a pair of elongated spaced wings rigidly secured to the lower end thereof received between said side members and extending forwardly at an acute angle to said post toward said plate;

a non-rotatable shaft extending through said apertures and said wings adjacent the bottom of said post;

means including annular bushings axially slidable along said shaft supporting said shaft in said apertures whereby said means serves as the pivotal support for said post;

spring means having one end engaging said post and a second end engaging said plate, said spring means, intermediate the ends, engaging the forward end of said wings and pivotally urging said post into forwardly erected position;

at least one clutch plate mounted on said shaft between each of said wings and the adjacent one of said side members;

means holding said clutch plates against rotation about said shaft and axially movable along said shaft;

a handle element threadably mounted on one end of said shaft for shifting said bushings axially of said shaft and forcing said clutch plates into tight frictional engagement with said wings when said handle element is rotated about said shaft.

15. In a chair having a seat frame and a back frame, said back frame having a post and means pivotably mounting said post to said seat frame, said means comprising:

a pair of spaced trunnion plates mounted to said chair frame;

a foot portion at the bottom of said post extending forwardly from said post, a pivot shaft mounted to said trunnion plates and secured to said post substantially at the junction of said post and foot portion;

a first plurality of clutch plates mounted on said shaft and axially movable along the same;

connector means securing said first clutch plates to said foot portion for rotation therewith about said shaft;

spring means urging said foot portion and first clutch plates into forwardly and downwardly rotated position;

a plurality of second clutch plates mounted on said shaft for axial sliding movement therealong interleaved alternately between said first clutch plates and means holding said second clutch plates against rotational movement about said shaft;

clamping means for forcing said first and second clutch plates axially of said shaft into tight side face to side face engagement for locking said foot portion and post against rotation about said shaft.