CA2089694A1 - Unitary spring for biasing a chair seat back support mechanism against a seat tilt mechanism - Google Patents
Unitary spring for biasing a chair seat back support mechanism against a seat tilt mechanismInfo
- Publication number
- CA2089694A1 CA2089694A1 CA 2089694 CA2089694A CA2089694A1 CA 2089694 A1 CA2089694 A1 CA 2089694A1 CA 2089694 CA2089694 CA 2089694 CA 2089694 A CA2089694 A CA 2089694A CA 2089694 A1 CA2089694 A1 CA 2089694A1
- Authority
- CA
- Canada
- Prior art keywords
- seat back
- seat
- back support
- housing
- arms
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 230000007246 mechanism Effects 0.000 title claims abstract description 121
- 239000000463 material Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- 235000004443 Ricinus communis Nutrition 0.000 description 1
- 208000027418 Wounds and injury Diseases 0.000 description 1
- 230000006835 compression Effects 0.000 description 1
- 238000007906 compression Methods 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000006378 damage Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 208000014674 injury Diseases 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
Classifications
-
- A—HUMAN NECESSITIES
- A47—FURNITURE; DOMESTIC ARTICLES OR APPLIANCES; COFFEE MILLS; SPICE MILLS; SUCTION CLEANERS IN GENERAL
- A47C—CHAIRS; SOFAS; BEDS
- A47C7/00—Parts, details, or accessories of chairs or stools
- A47C7/36—Supports for the head or the back
- A47C7/40—Supports for the head or the back for the back
- A47C7/44—Supports for the head or the back for the back with elastically-mounted back-rest or backrest-seat unit in the base frame
- A47C7/443—Supports for the head or the back for the back with elastically-mounted back-rest or backrest-seat unit in the base frame with coil springs
Landscapes
- Chairs Characterized By Structure (AREA)
Abstract
ABSTRACT
An improved mechanism for biasing a seat back with respect to a seat tilt mechanism is disclosed. The improved mechanism includes a unitary spring having two coil springs interconnected by a loop. Each coil has an arm extending therefrom and the two arms are parallel. The arms and loop are integrally formed with the coils to form the unitary spring. The seat tilt mechanism is attachable to the underside of a chair seat and a seat back support bracket is pivotally attached to the seat tilt mechanism at the back of the chair seat. A seat back support arm is attached at one end to the seat back and the other end is attached to the seat back support mechanism. The unitary spring is disposed between the seat tilt mechanism and the seat back support mechanism to bias the latter with respect to the former. The unitary spring is positioned so that if the loop bears against the edge of the seat tilt mechanism housing then the arms bear against a portion of the seat back support bracket and vice versa. With no force applied against the seat back the unitary spring biases the seat back to the upright position. When a user leans back against the seat back the latter pivots about the pivotal connection against the spring thereby a restoring force in the spring which returns the seat back to the upright position. The improved biasing mechanism exhibits a significantly longer lifetime than the prior art device which uses two spaced and independent jack springs.
An improved mechanism for biasing a seat back with respect to a seat tilt mechanism is disclosed. The improved mechanism includes a unitary spring having two coil springs interconnected by a loop. Each coil has an arm extending therefrom and the two arms are parallel. The arms and loop are integrally formed with the coils to form the unitary spring. The seat tilt mechanism is attachable to the underside of a chair seat and a seat back support bracket is pivotally attached to the seat tilt mechanism at the back of the chair seat. A seat back support arm is attached at one end to the seat back and the other end is attached to the seat back support mechanism. The unitary spring is disposed between the seat tilt mechanism and the seat back support mechanism to bias the latter with respect to the former. The unitary spring is positioned so that if the loop bears against the edge of the seat tilt mechanism housing then the arms bear against a portion of the seat back support bracket and vice versa. With no force applied against the seat back the unitary spring biases the seat back to the upright position. When a user leans back against the seat back the latter pivots about the pivotal connection against the spring thereby a restoring force in the spring which returns the seat back to the upright position. The improved biasing mechanism exhibits a significantly longer lifetime than the prior art device which uses two spaced and independent jack springs.
Description
6 ~
FIELD OF T~E INVENTION
The present invention relates to a mechanism for biasing a seat back with respect to a seat tilt mechanism.
BACKGROUND OF THE IN~IENTION
Comfortable and user friendly office equipment which can be readily adapted to a user's individual needs is a prerequisite for creating an office work environment conducive to maximum productivity. Office chairs are an integral part of any office environment and chalrs having features which can be adjusted -to meet a user's posture requirements clearly play a pivotal role in contributing to a user's comfort level. In particular, chairs having tiltable backrests or seat backs are important Eor adapting the chair to the user's posture requirements. The chair seat back is attached to the seat by a support arm which is attached at one end to the seat back while the other end is attached to a seat back support mechanism which in turn is attached to the chair.
Prior art seat back support mechanisms are pivotally attached to a seat tilt mechanism which is attached to the underside of the chair seat. The pivotal connection is formed by a rod extending between and through the side walls of the support mechanism and the housing of the tilt mechanism. The seat back support mechanism is biased with respect to the seat tilt mechanism by a pair of independent, spaced jack springs. The jack springs each include a spring coil and a pair of arms, one attached to 2 a ~
each end of the coil and extending away from the coil. The springs are mounted on the rod which passes through the coils. One arm of each spring bears against a portion of the seat tilt mechanism and the other arm of each spring bears against a portion of the seat back support mechanism.
The seat tilt mechanism is fixed with respect to the chair seat so that when user leans back against the seat back, the seat back pivots backwards against the force of the jack springs. When the user leans forward, the jack springs act to return the height adjustment mechanism and hence the seat back, back to the upright position.
A major drawback to this arrangement is that over time one of the springs is prone to weaken much more rapidly than the other which produces a noticeable effect on the balance of the seat back. Further, it has been observed that after about 1x105 cycles of the seat back oscillating back and forth, one of the jack springs breaks leading to an unbalanced seat back. This is a potentially dangerous situation since if the other spring breaks a user could fall backwards in the chair which could lead to injury.
Accordingly, it would be advantageous to provide an improved mechanism for biasing a seat back with respect to a chair seat which exhibits a longer lifetime and is less prone to becoming unbalanced.
SUMMARY OF T~E INVENTION
The present invention provides a seat back .
:~ . . :-.
-~, ~. ,; `
20~9~
support mechanism biased with respect to a chair seat tilt mechanism. The seat back support mechanism includes a mounting bracket and the chair seat tilt mechanism is provided with a housing which is attachable to the underside of a chair. The mounting bracket is pivotally attached to the housing adjacent to an end portion thereof.
The seat back support mechanism biased with respect to the seat tilt mechanism comprises a unitary spring having at least two axially aligned spaced coil spring portions with each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop. The unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of a portion of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said seat tilt mechanism housing.
In another aspect of the invention there is provided an impoved chair. The chair is of the type having a seat tilt mechanism attached to the underside of a chair seat. The seat tilt mechanism is provided with a housing and the chair has a seat back with a seat back support arm attached thereto. The chair inlcudes a seat back support mechanism comprising a mounting bracket pivotally attached to an end portion of the housing. The seat back support arm is attached to the mounting bracket. The chair ~$~
includes spring means for biasing the mounting bracket with respect to the housing. The improvement comprises the spring means having at least two axially aligned spaced coil spring portions with each coil spring portion S terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop and unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of the portion of the seat back support bracket or the edge of the seat tilt mechanism housing.
In another aspect of the invention a chair having a tiltable seat back is provided. The chair includes a chair base and a seat attached to the chair base. The chair has a seat back having a seat back support arm connected at one end to the seat back. A seat tilt mechanism is provided with a housing and is attachable to an underside of the seat. The chair is provided with a seat back support mechanism comprising a mounting bracket pivotally attached to the housing. The seat back support arm is attached to the mounting bracket. The chair includes a unitary spring for biasing the mounting bracket with respect to the seat tilt mechanism so that the seat back is biased forward in a substantially vertical position. The unitary spring means comprises at least two ,, . ~ :
:
, ~:
2 ~
axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop. Ihe unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or the edge of the seat tilt mechanism housing.
BRIEF DESCRIPTION OF T~E DRAWINGS
The following is a description, by way of example only, of an improved mechanism for biasing a seat back with respect to a chair seat using a unitary spring in accordance with the subject invention, reference being had to the accompanying drawings, in which;
Figure 1 is a perspective view of a chair provided with a seat back biased with respect to the seat using the unitary spring embodying the subject invention;
Figures 2 to 4 illustrate different seat back support mechanisms which may be used with the unitary spring of the present invention;
Figure 5 is a disassembled perspective view of a prior art spring mechanism for biasing a seat back support mechanism with respect to a seat tilt mechanism;
Figure 6 is a disassembled perspective view - .;
:: : : . :
, :: `'., ' '~ :
2 ~
similar to Figure 5 showing a unitary spring of the present invention for biasing a seat back support mechanism with respect to a seat tilt mechanism;
Figure 7 is a perspective view of the apparatus of Figure 6 assembled;
Figure 8 is a perspective view similar to Figure 6 showing another embodiment of the unitary spring;
Figure 9 is a perspective view of the apparatus of Figure 8 assembled; and Figure 10 is a perspective view similar to Figure 9 showing another embodiment of the unitary spring.
DETAILED DE~CRIPTION OF THE INVENTION
In the ensuing description of the structure and operation of the prior art and the new, inventive mechanism for biasing a chair seat back with respect to a seat tilt mechanism, reference will be made to the Figures wherein like numerals refer to like parts. Referring first to Figure l, there is shown a chair 10 of the type generally found in an office environment. Chair 10 includes supporting legs 12 each having a castor 14 attached at a lower end thereof. Legs 12 extend radially from a spindle support 16 which supports a spindle 18 which in turn is attached to a chair seat support 20. A seat cushion, not shown, is attachable to the top surface of seat support 20.
Chair 10 is provided with a seat back 22 attached to one end of a seat back support arm 24. The other end of support arm 24 is attached to a seat back support mechanism 2 ~ 2 ~
indicated generally by numeral 26.
Chair 10 is provided with a seat tilt mechanism 30 secured to the bottom surface of seat support 20. Seat tilt mechanism 30 comprises a housing 32 having side walls 34. A seat bias spring, not shown, is enclosed in housing 32. Seat tilt mechanism 30 includes a locking arm 36 for locking and unlocking the seat bias spring. Locking arm 36 is movable between a first position in which the chair seat is locked in the horizontal position and a second position in which the chair seat is unlocked and may be tilted against the seat bias spring with respect to spindle 18.
Further details of the structure and operation of the seat spring and locking arm 36 will be known to those skilled in the art and will not be further discussed.
Seat back support mechanism 26 used in the present invention may have several embodiments. Figures 2, 3, and 4 show three embodiments 26a, 26b and 26c respectively of seat back support mechanism 26 which may be used. Seat support mechanisms 26a and 26b each comprise a different height adjustment mechanism for adjusting the height of the seat back attached to support arm 24. Seat back support mechanism 26c of Figure 4 comprises seat back support arm 24 rigidly secured to the support mechanism, such as by welding or using bolts, not shown. Support mechanisms 26a, 26b and 26c each includes a mounting bracket 50 having an end wall 52 and opposing side walls 54 attached thereto with each side wall provided with a hole 56 extending therethrough. A rod 58 extends between and :: : .,. , :
' ' '' ' '-' '' ' : ' ~9~
through side walls 54 of the bracket spaced above the bottom edge of the bracket.
Seat back support mechanism 26a is provided with a height adjustment mechanism comprising a cam 70 rotatably mounted in side walls 54 and extending therebetween. Cam 70 includes a handle 72 for rotating the cam. A plastic insert 74 is dimensioned to snap fit into mounting bracket 50 against the interior face of end wall 52. Insert 74 includes a connector member 75 extending between the sides of the insert spaced from the interior face of end wall 50 and below the upper edge of the insert to form a gap 77.
Connector member 75 is provided with a raised portion 76 dimensioned and positioned to be moved inwardly toward end wall 52 by cam 70 when the latter is rotated to the locking position. Seat back support arm 24 is inserted through gap 77 with cam 70 disengaged from raised portion 76 and arm 24 is locked at the desired height by rotating cam 70 into engagement with raised portion 76 thereby compressing arm 24 between the cam and back wall 52.
Seat back support mechanism 26b differs from support mechanism 26a in that the former utilizes an improved cam 80. Cam 80 is rotatably mounted in side walls 54 and extends therebetween and includes a handle 82. Cam 80 comprises a plurality of planar faces 84 extending therealong parallel to the cam axis of rotation. The length of the radial line extending perpendicularly from -the rotational axis of the cam to each planar face increases steadily around the circumference of the cam so , ..
:::
- . : . - :::: . :
: . :: - :. :: :.: :
2 ~
that rotation of cam 80 causes the gap between the cam and back wall 52 to change. Support arm 24 is inserted through this gap in bracket 50 and when seat back 22 has been adjusted to the desired height, cam 80 is rotated until it lockingly engages support arm 24. In the locked position one of the planar faces 84 will be contiguous with the surface of arm 24. Further structural and operational details of this height adjustment mechanism are disclosed in copending United States Patent Application Serial No.
Details of the prior art method of biasing the seat support mechanism with respect to seat tilt mechanism 30 will now be discussed with reference to Figures 4 and 5.
Seat back support mechanism 26 is pivotally attached to housing 32 of seat tilt mechanism 30 by a rod 90 extending through holes 56 in side walls 54 and holes 92 located in side walls 34 of housing 32.
Seat back support mechanism 26 is spring biased with respect to tilt mechanism 30 by a pair of spaced jack springs 92 disposed between the seat support mechanism and seat tilt mechanism 30. Each spring 92 comprises a coil spring portion 94 and spring arms 96 and 98 extending divergently from coil portion. Springs 92 are mounted spaced apart with rod 90 extending through coil portions 94. Arms 96 bear against rod 58 in bracket 50 while arms 98 bear against an edge lO0 of housing 32 and are located each in a recess 102 disposed along edge lO0 which has a pair of recesses 102 separated by a lip 104. Springs 92 .~
-- :
.
2~9~
bear on rod 58 in such a way that end wall 52 of bracket 50 is biased upwardly, best seen in Figure 4, thereby maintaining seat back 22 (Figure 1) in the vertical position. A user leaning back against seat back 22 forces bracket 50 to pivot about rod 90 thereby compressing arms 96 and 98 together. Compression of arms 96 and 98 together generates a restoring force which pivots bracket 50 in the opposite direction when the user leans forward thereby returning the seat back 22 to the upright position.
Referring now to Figures 6 to 9, various embodiments of a unitary spring comprising the subject invention are shown for biasing seat back support mechanism 26 with respect to seat tilt mechanism 30.
Figure 6 shows a unitary spring 110 comprising two spaced coil spring portions 112 and 114 mounted on rod 90. Coil portions 112 and 114 are interconnected by a U-shaped loop 116 formed by two arms 117 extending tangentially from the coil portions and a connecting cross member 119. Each coil spring portion 112 and 114 has an integrally formed arm 118 extending tangentially therefrom.
Arms 118 are substantially parallel and extend from coils 112 and 114 at an angle A less than 180 with respect to the plane defined by loop 116. The precise angle A will be determined by the spacing between rod 58 and edge 100.
Rectangular loop 116 acts to maintain coil portions 112 and 114 in fixed spaced relationship. Loop 116 is dimensioned so that the upper portions of arms 117 are located in recesses 102 in edge 100 of housing 32 and lip 104 fits ., ~
2~3~
snugly between arms 117. When assembled, arms 11~ bear against rod 58, best seen in Figure 7. The coil portions 112 and 114 are not movable independent of each other because spring 110 is a unitary spring (one piece construction) and is dimensioned to fit squarely between housing 32 and bracket 50.
Figures 8 and 9 illustrate another embodiment of a unitary spring 130 forming the subject invention. Spring 130 is similar to spring 110 except that the spring is mounted on rod 90 with a looped portion 132 interconnecting coil portions 112 and 114 which bears against rod 58.
Also, individual arms 118 bear against edge 100 in recesses 102 of housing 32 when bracket 50 is pivotally attached to housing 32. Loop 132 is shaped to provide the desired angle of tilt of bracket 50 with respect to housing 32 when seat back 22 (Figure 1) is in the upright position. Coil spring portions 112 and 114 are not independently movable since they are interconnected by loop 132 so that during use spring 130 remains square on rod 90.
It will be appreciated that a unitary spring having two sets of loops formed with the coil portions could also be used as shown in Figure 10. The second loop could be made by welding the ends of arms 118 together. In this embodiment one of the loops bears against edge 100 of housing 32 and the other bears against rod 58 located in bracket 50.
Those skilled in the art will readily appreciate .-the various kinds of stock material having different .
., ~,." :' 2 ~ J ~.-'L
compositions and gauge which may be used in the fabrication of the unitary spring disclosed herein.
The use of the unitary spring forming the subject invention has resulted in a dramatic and surprising lifetime increase of the seat back tilt function. As described earlier, liEetime testing using the separate, independent prior art springs showed that one of the springs consistently failed after about lx105 tilt cycles of the seat back. Lifetime studies using the unitary spring disclosed herein indicated a minimum lifetime of 2X106 tilt cycles was obtainable. The actual mean lifetime of the unitary spring is unknown since no failures were recorded after 2x1G6 tilt cycles and the tests were stopped after this point.
The dramatic improvement in lifetime achieved by using the unitary spring is attributable in part to the fact that there is no independent movement of the two coil spring portions in the unitary spring since the coils are coupled together. In the prior art mechanism the two springs 92 can shift around on rod 90 independent of each other. This tends to lead to uneven stresses on the arms in the two coil springs thereby resulting in the most stressed spring failing first. By comparison, the unitary spring of the present invention is mounted in such a way that the spring arms remain fixed with respect to the coil portions, thereby reducing the opportunity for uneven stresses to develop in the arms.
Another factor which may be contributing to the 2~9~4 failure of the individual springs is that the two independent springs may be fabricated from completely different stock material. Therefore, there is a significant probability that one of the springs may have a higher concentration of internal flaws which would result in that spring being much weaker than the other spring of the pair. This spring would therefore degrade much quicker than if both springs were vf the same quality. The unitary spring, being fabricated from the same stock material, should therefore be expected to exhibit a longer lifetime.
The unitary spring for use with the chair seat back support mechanism and the seat tilt mechanism may be assembled with tha rest of the chair at the time of assembly of the chair. Alternatively, chairs provided with the prior art separate seat back bias springs may be retrofitted with the unitary spring disclosed herein.
While the unitary spring of the present invention used to bias the chair seat back support mechanism with respect to the seat tilt mechanism has been described and illustrated with respect to various embodiments, it will be appreciated that numerous variations of thees embodiments may be made without departing from the scope of the invention.
:
, ~ .
FIELD OF T~E INVENTION
The present invention relates to a mechanism for biasing a seat back with respect to a seat tilt mechanism.
BACKGROUND OF THE IN~IENTION
Comfortable and user friendly office equipment which can be readily adapted to a user's individual needs is a prerequisite for creating an office work environment conducive to maximum productivity. Office chairs are an integral part of any office environment and chalrs having features which can be adjusted -to meet a user's posture requirements clearly play a pivotal role in contributing to a user's comfort level. In particular, chairs having tiltable backrests or seat backs are important Eor adapting the chair to the user's posture requirements. The chair seat back is attached to the seat by a support arm which is attached at one end to the seat back while the other end is attached to a seat back support mechanism which in turn is attached to the chair.
Prior art seat back support mechanisms are pivotally attached to a seat tilt mechanism which is attached to the underside of the chair seat. The pivotal connection is formed by a rod extending between and through the side walls of the support mechanism and the housing of the tilt mechanism. The seat back support mechanism is biased with respect to the seat tilt mechanism by a pair of independent, spaced jack springs. The jack springs each include a spring coil and a pair of arms, one attached to 2 a ~
each end of the coil and extending away from the coil. The springs are mounted on the rod which passes through the coils. One arm of each spring bears against a portion of the seat tilt mechanism and the other arm of each spring bears against a portion of the seat back support mechanism.
The seat tilt mechanism is fixed with respect to the chair seat so that when user leans back against the seat back, the seat back pivots backwards against the force of the jack springs. When the user leans forward, the jack springs act to return the height adjustment mechanism and hence the seat back, back to the upright position.
A major drawback to this arrangement is that over time one of the springs is prone to weaken much more rapidly than the other which produces a noticeable effect on the balance of the seat back. Further, it has been observed that after about 1x105 cycles of the seat back oscillating back and forth, one of the jack springs breaks leading to an unbalanced seat back. This is a potentially dangerous situation since if the other spring breaks a user could fall backwards in the chair which could lead to injury.
Accordingly, it would be advantageous to provide an improved mechanism for biasing a seat back with respect to a chair seat which exhibits a longer lifetime and is less prone to becoming unbalanced.
SUMMARY OF T~E INVENTION
The present invention provides a seat back .
:~ . . :-.
-~, ~. ,; `
20~9~
support mechanism biased with respect to a chair seat tilt mechanism. The seat back support mechanism includes a mounting bracket and the chair seat tilt mechanism is provided with a housing which is attachable to the underside of a chair. The mounting bracket is pivotally attached to the housing adjacent to an end portion thereof.
The seat back support mechanism biased with respect to the seat tilt mechanism comprises a unitary spring having at least two axially aligned spaced coil spring portions with each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop. The unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of a portion of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said seat tilt mechanism housing.
In another aspect of the invention there is provided an impoved chair. The chair is of the type having a seat tilt mechanism attached to the underside of a chair seat. The seat tilt mechanism is provided with a housing and the chair has a seat back with a seat back support arm attached thereto. The chair inlcudes a seat back support mechanism comprising a mounting bracket pivotally attached to an end portion of the housing. The seat back support arm is attached to the mounting bracket. The chair ~$~
includes spring means for biasing the mounting bracket with respect to the housing. The improvement comprises the spring means having at least two axially aligned spaced coil spring portions with each coil spring portion S terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop and unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of the portion of the seat back support bracket or the edge of the seat tilt mechanism housing.
In another aspect of the invention a chair having a tiltable seat back is provided. The chair includes a chair base and a seat attached to the chair base. The chair has a seat back having a seat back support arm connected at one end to the seat back. A seat tilt mechanism is provided with a housing and is attachable to an underside of the seat. The chair is provided with a seat back support mechanism comprising a mounting bracket pivotally attached to the housing. The seat back support arm is attached to the mounting bracket. The chair includes a unitary spring for biasing the mounting bracket with respect to the seat tilt mechanism so that the seat back is biased forward in a substantially vertical position. The unitary spring means comprises at least two ,, . ~ :
:
, ~:
2 ~
axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof. The first arms are integrally connected to form a loop. Ihe unitary spring is disposed between the mounting bracket and the seat tilt mechanism with the loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or the edge of the seat tilt mechanism housing.
BRIEF DESCRIPTION OF T~E DRAWINGS
The following is a description, by way of example only, of an improved mechanism for biasing a seat back with respect to a chair seat using a unitary spring in accordance with the subject invention, reference being had to the accompanying drawings, in which;
Figure 1 is a perspective view of a chair provided with a seat back biased with respect to the seat using the unitary spring embodying the subject invention;
Figures 2 to 4 illustrate different seat back support mechanisms which may be used with the unitary spring of the present invention;
Figure 5 is a disassembled perspective view of a prior art spring mechanism for biasing a seat back support mechanism with respect to a seat tilt mechanism;
Figure 6 is a disassembled perspective view - .;
:: : : . :
, :: `'., ' '~ :
2 ~
similar to Figure 5 showing a unitary spring of the present invention for biasing a seat back support mechanism with respect to a seat tilt mechanism;
Figure 7 is a perspective view of the apparatus of Figure 6 assembled;
Figure 8 is a perspective view similar to Figure 6 showing another embodiment of the unitary spring;
Figure 9 is a perspective view of the apparatus of Figure 8 assembled; and Figure 10 is a perspective view similar to Figure 9 showing another embodiment of the unitary spring.
DETAILED DE~CRIPTION OF THE INVENTION
In the ensuing description of the structure and operation of the prior art and the new, inventive mechanism for biasing a chair seat back with respect to a seat tilt mechanism, reference will be made to the Figures wherein like numerals refer to like parts. Referring first to Figure l, there is shown a chair 10 of the type generally found in an office environment. Chair 10 includes supporting legs 12 each having a castor 14 attached at a lower end thereof. Legs 12 extend radially from a spindle support 16 which supports a spindle 18 which in turn is attached to a chair seat support 20. A seat cushion, not shown, is attachable to the top surface of seat support 20.
Chair 10 is provided with a seat back 22 attached to one end of a seat back support arm 24. The other end of support arm 24 is attached to a seat back support mechanism 2 ~ 2 ~
indicated generally by numeral 26.
Chair 10 is provided with a seat tilt mechanism 30 secured to the bottom surface of seat support 20. Seat tilt mechanism 30 comprises a housing 32 having side walls 34. A seat bias spring, not shown, is enclosed in housing 32. Seat tilt mechanism 30 includes a locking arm 36 for locking and unlocking the seat bias spring. Locking arm 36 is movable between a first position in which the chair seat is locked in the horizontal position and a second position in which the chair seat is unlocked and may be tilted against the seat bias spring with respect to spindle 18.
Further details of the structure and operation of the seat spring and locking arm 36 will be known to those skilled in the art and will not be further discussed.
Seat back support mechanism 26 used in the present invention may have several embodiments. Figures 2, 3, and 4 show three embodiments 26a, 26b and 26c respectively of seat back support mechanism 26 which may be used. Seat support mechanisms 26a and 26b each comprise a different height adjustment mechanism for adjusting the height of the seat back attached to support arm 24. Seat back support mechanism 26c of Figure 4 comprises seat back support arm 24 rigidly secured to the support mechanism, such as by welding or using bolts, not shown. Support mechanisms 26a, 26b and 26c each includes a mounting bracket 50 having an end wall 52 and opposing side walls 54 attached thereto with each side wall provided with a hole 56 extending therethrough. A rod 58 extends between and :: : .,. , :
' ' '' ' '-' '' ' : ' ~9~
through side walls 54 of the bracket spaced above the bottom edge of the bracket.
Seat back support mechanism 26a is provided with a height adjustment mechanism comprising a cam 70 rotatably mounted in side walls 54 and extending therebetween. Cam 70 includes a handle 72 for rotating the cam. A plastic insert 74 is dimensioned to snap fit into mounting bracket 50 against the interior face of end wall 52. Insert 74 includes a connector member 75 extending between the sides of the insert spaced from the interior face of end wall 50 and below the upper edge of the insert to form a gap 77.
Connector member 75 is provided with a raised portion 76 dimensioned and positioned to be moved inwardly toward end wall 52 by cam 70 when the latter is rotated to the locking position. Seat back support arm 24 is inserted through gap 77 with cam 70 disengaged from raised portion 76 and arm 24 is locked at the desired height by rotating cam 70 into engagement with raised portion 76 thereby compressing arm 24 between the cam and back wall 52.
Seat back support mechanism 26b differs from support mechanism 26a in that the former utilizes an improved cam 80. Cam 80 is rotatably mounted in side walls 54 and extends therebetween and includes a handle 82. Cam 80 comprises a plurality of planar faces 84 extending therealong parallel to the cam axis of rotation. The length of the radial line extending perpendicularly from -the rotational axis of the cam to each planar face increases steadily around the circumference of the cam so , ..
:::
- . : . - :::: . :
: . :: - :. :: :.: :
2 ~
that rotation of cam 80 causes the gap between the cam and back wall 52 to change. Support arm 24 is inserted through this gap in bracket 50 and when seat back 22 has been adjusted to the desired height, cam 80 is rotated until it lockingly engages support arm 24. In the locked position one of the planar faces 84 will be contiguous with the surface of arm 24. Further structural and operational details of this height adjustment mechanism are disclosed in copending United States Patent Application Serial No.
Details of the prior art method of biasing the seat support mechanism with respect to seat tilt mechanism 30 will now be discussed with reference to Figures 4 and 5.
Seat back support mechanism 26 is pivotally attached to housing 32 of seat tilt mechanism 30 by a rod 90 extending through holes 56 in side walls 54 and holes 92 located in side walls 34 of housing 32.
Seat back support mechanism 26 is spring biased with respect to tilt mechanism 30 by a pair of spaced jack springs 92 disposed between the seat support mechanism and seat tilt mechanism 30. Each spring 92 comprises a coil spring portion 94 and spring arms 96 and 98 extending divergently from coil portion. Springs 92 are mounted spaced apart with rod 90 extending through coil portions 94. Arms 96 bear against rod 58 in bracket 50 while arms 98 bear against an edge lO0 of housing 32 and are located each in a recess 102 disposed along edge lO0 which has a pair of recesses 102 separated by a lip 104. Springs 92 .~
-- :
.
2~9~
bear on rod 58 in such a way that end wall 52 of bracket 50 is biased upwardly, best seen in Figure 4, thereby maintaining seat back 22 (Figure 1) in the vertical position. A user leaning back against seat back 22 forces bracket 50 to pivot about rod 90 thereby compressing arms 96 and 98 together. Compression of arms 96 and 98 together generates a restoring force which pivots bracket 50 in the opposite direction when the user leans forward thereby returning the seat back 22 to the upright position.
Referring now to Figures 6 to 9, various embodiments of a unitary spring comprising the subject invention are shown for biasing seat back support mechanism 26 with respect to seat tilt mechanism 30.
Figure 6 shows a unitary spring 110 comprising two spaced coil spring portions 112 and 114 mounted on rod 90. Coil portions 112 and 114 are interconnected by a U-shaped loop 116 formed by two arms 117 extending tangentially from the coil portions and a connecting cross member 119. Each coil spring portion 112 and 114 has an integrally formed arm 118 extending tangentially therefrom.
Arms 118 are substantially parallel and extend from coils 112 and 114 at an angle A less than 180 with respect to the plane defined by loop 116. The precise angle A will be determined by the spacing between rod 58 and edge 100.
Rectangular loop 116 acts to maintain coil portions 112 and 114 in fixed spaced relationship. Loop 116 is dimensioned so that the upper portions of arms 117 are located in recesses 102 in edge 100 of housing 32 and lip 104 fits ., ~
2~3~
snugly between arms 117. When assembled, arms 11~ bear against rod 58, best seen in Figure 7. The coil portions 112 and 114 are not movable independent of each other because spring 110 is a unitary spring (one piece construction) and is dimensioned to fit squarely between housing 32 and bracket 50.
Figures 8 and 9 illustrate another embodiment of a unitary spring 130 forming the subject invention. Spring 130 is similar to spring 110 except that the spring is mounted on rod 90 with a looped portion 132 interconnecting coil portions 112 and 114 which bears against rod 58.
Also, individual arms 118 bear against edge 100 in recesses 102 of housing 32 when bracket 50 is pivotally attached to housing 32. Loop 132 is shaped to provide the desired angle of tilt of bracket 50 with respect to housing 32 when seat back 22 (Figure 1) is in the upright position. Coil spring portions 112 and 114 are not independently movable since they are interconnected by loop 132 so that during use spring 130 remains square on rod 90.
It will be appreciated that a unitary spring having two sets of loops formed with the coil portions could also be used as shown in Figure 10. The second loop could be made by welding the ends of arms 118 together. In this embodiment one of the loops bears against edge 100 of housing 32 and the other bears against rod 58 located in bracket 50.
Those skilled in the art will readily appreciate .-the various kinds of stock material having different .
., ~,." :' 2 ~ J ~.-'L
compositions and gauge which may be used in the fabrication of the unitary spring disclosed herein.
The use of the unitary spring forming the subject invention has resulted in a dramatic and surprising lifetime increase of the seat back tilt function. As described earlier, liEetime testing using the separate, independent prior art springs showed that one of the springs consistently failed after about lx105 tilt cycles of the seat back. Lifetime studies using the unitary spring disclosed herein indicated a minimum lifetime of 2X106 tilt cycles was obtainable. The actual mean lifetime of the unitary spring is unknown since no failures were recorded after 2x1G6 tilt cycles and the tests were stopped after this point.
The dramatic improvement in lifetime achieved by using the unitary spring is attributable in part to the fact that there is no independent movement of the two coil spring portions in the unitary spring since the coils are coupled together. In the prior art mechanism the two springs 92 can shift around on rod 90 independent of each other. This tends to lead to uneven stresses on the arms in the two coil springs thereby resulting in the most stressed spring failing first. By comparison, the unitary spring of the present invention is mounted in such a way that the spring arms remain fixed with respect to the coil portions, thereby reducing the opportunity for uneven stresses to develop in the arms.
Another factor which may be contributing to the 2~9~4 failure of the individual springs is that the two independent springs may be fabricated from completely different stock material. Therefore, there is a significant probability that one of the springs may have a higher concentration of internal flaws which would result in that spring being much weaker than the other spring of the pair. This spring would therefore degrade much quicker than if both springs were vf the same quality. The unitary spring, being fabricated from the same stock material, should therefore be expected to exhibit a longer lifetime.
The unitary spring for use with the chair seat back support mechanism and the seat tilt mechanism may be assembled with tha rest of the chair at the time of assembly of the chair. Alternatively, chairs provided with the prior art separate seat back bias springs may be retrofitted with the unitary spring disclosed herein.
While the unitary spring of the present invention used to bias the chair seat back support mechanism with respect to the seat tilt mechanism has been described and illustrated with respect to various embodiments, it will be appreciated that numerous variations of thees embodiments may be made without departing from the scope of the invention.
:
, ~ .
Claims (21)
1. A seat back support mechanism biased with respect to a chair seat tilt mechanism, the seat back support mechanism including a mounting bracket and the chair seat tilt mechanism including a housing and being attachable to the underside of a chair, the mounting bracket being pivotally attached to the housing adjacent to an end portion thereof, comprising;
a unitary spring having at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of a portion of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said seat tilt mechanism housing.
a unitary spring having at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of a portion of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said seat tilt mechanism housing.
2. The biased seat back support mechanism according to claim 1 wherein said first arms are substantially parallel and said loop defines a plane, and wherein said second arms are disposed at an angle of less than 180 with respect to said plane.
3. The biased seat back support mechanism according to claim 2 wherein said mounting bracket is a rectangular U-shaped bracket having two spaced side walls attached to a back wall, said housing also having side walls, a rod extending between said bracket side walls and said housing side walls and through said coil spring portions.
4. The biased seat seat back support mechanism according to claim 3 including a plurality of spaced recesses located along said edge of said housing end portion for receiving therein the spaced arms of said loop or the arms of said unitary spring bearing thereagainst for maintaining said unitary spring in fixed relationship with said housing and said mounting bracket.
5. The biased seat back support mechanism according to claim 1 wherein said second arms are integrally connected at the ends thereof to form a further loop.
6. The biased seat back support mechanism according to claim 4 including a seat back support arm rigidly secured to said mounting bracket, a chair seat back being attachable to said seat back support arm.
7. The biased seat back support mechanism according to claim 4 wherein said seat back support mechanism includes a seat back support arm and a height adjustment mechanism therefor, said height adjustment mechanism comprising a cam rotatably mounted between said bracket side walls and spaced from said bracket back wall, said seat back support arm being receivable between said cam and said back wall and lockable therebetween by rotating said cam.
8. In a chair of the type provided with a seat tilt mechanism attached to the underside of a chair seat, the seat tilt mechanism provided with a housing, the chair having a seat back with a seat back support arm attached thereto and also having a seat back support mechanism comprising a mounting bracket pivotally attached to an end portion of said housing, said seat back support arm being attached to said mounting bracket, the chair including spring means for biasing said mounting bracket with respect to said housing, the improvement wherein;
said spring means comprises at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said edge of the seat tilt mechanism housing.
said spring means comprises at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said edge of the seat tilt mechanism housing.
9. The chair according to claim 8 wherein said first arms are substantially parallel and said loop defines a plane, and wherein said second arms are disposed at an angle of less than 180 with respect to said plane.
10. The chair according to claim 9 wherein said mounting bracket is a rectangular U-shaped bracket having two spaced side walls attached to a back wall, said housing also having side walls, a rod extending between said bracket side walls and said housing side walls and through said coil spring portions.
11. The chair according to claim 10 including a plurality of spaced recesses located along said edge of said housing end portion for receiving therein the spaced arms of said loop or the arms of said unitary spring bearing thereagainst for maintaining said unitary spring in fixed relationship with said housing and said mounting bracket.
12. The chair according to claim 8 wherein said second arms are integrally connected at the ends thereof to form a further loop.
13. The chair according to claim 10 wherein said seat back support arm is rigidly secured to said mounting bracket.
14. The chair according to claim 10 wherein said seat back support mechanism comprises a height adjustment mechanism for the seat back, said height adjustment mechanism comprising a cam rotatably mounted between said bracket side walls and spaced from said back wall, the seat back support arm being receivable between said cam and said back wall and lockable therebetween by rotating said cam.
15. A chair having a tiltable seat back, comprising;
a) a chair base and a seat attached to said chair base;
b) a seat back having a seat back support arm connected at one end to said seat back;
c) a seat tilt mechanism provided with a housing and attachable to an underside of said seat; and d) a seat back support mechanism comprising a mounting bracket pivotally attached to said housing adjacent to an end portion of the housing, said seat back support arm being attached to said mounting bracket, a unitary spring for biasing the mounting bracket with respect to the seat tilt mechanism so that said seat back is biased forward into a substantially vertical position, said unitary spring means comprises at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said edge of the seat tilt mechanism housing.
a) a chair base and a seat attached to said chair base;
b) a seat back having a seat back support arm connected at one end to said seat back;
c) a seat tilt mechanism provided with a housing and attachable to an underside of said seat; and d) a seat back support mechanism comprising a mounting bracket pivotally attached to said housing adjacent to an end portion of the housing, said seat back support arm being attached to said mounting bracket, a unitary spring for biasing the mounting bracket with respect to the seat tilt mechanism so that said seat back is biased forward into a substantially vertical position, said unitary spring means comprises at least two axially aligned spaced coil spring portions, each coil spring portion terminating in a first arm extending tangentially from one end thereof and a second arm extending from the other end thereof, said first arms being integrally connected to form a loop, said unitary spring being disposed between said mounting bracket and said seat tilt mechanism with said loop bearing against one of an edge of the seat tilt mechanism housing or a portion of the seat back support bracket and the arms bearing against the other of said portion of the seat back support bracket or said edge of the seat tilt mechanism housing.
16. The chair according to claim 15 wherein said arms are substantially parallel, said loop defines a plane, and said arms are disposed at an angle of less than 180 with respect to said plane.
17. The chair according to claim 16 wherein said mounting bracket is a rectangular U-shaped bracket having two spaced side walls and a back wall, said housing also having spaced side walls, including a rod extending between said bracket side walls and said housing side walls and through said coil spring portions.
18. The chair according to claim 17 including a plurality of spaced recesses located along said edge of said housing end portion for receiving therein the spaced arms of said loop or the arms of said unitary spring bearing thereagainst for maintaining said unitary spring in fixed relationship with said housing and said mounting bracket.
19. The chair according to claim 16 wherein said second arms are integrally connected to form a further loop.
20. The chair according to claim 17 wherein said seat back support arm is rigidly secured to said mounting bracket.
21. The chair according to claim 17 wherein said seat back support mechanism comprises a height adjustment mechanism for the seat back, said height adjustment mechanism comprising a cam rotatably mounted between said mounting bracket side walls and spaced from said back wall, the seat back support arm being receivable between said cam and said back wall and lockable therebetween by rotating said cam.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US91915292A | 1992-07-23 | 1992-07-23 | |
| US07/919,152 | 1992-07-23 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2089694A1 true CA2089694A1 (en) | 1994-01-24 |
Family
ID=25441598
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2089694 Abandoned CA2089694A1 (en) | 1992-07-23 | 1993-02-17 | Unitary spring for biasing a chair seat back support mechanism against a seat tilt mechanism |
Country Status (3)
| Country | Link |
|---|---|
| AU (1) | AU4556193A (en) |
| CA (1) | CA2089694A1 (en) |
| WO (1) | WO1994002052A1 (en) |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB383407A (en) * | 1931-11-10 | 1932-11-17 | Tan Sad Chair Co 1931 Ltd | An improved adjustable backrest or back support for a seat |
| US3093413A (en) * | 1962-02-21 | 1963-06-11 | Jr Charles W Chancellor | Chair with double pivot spring assembly |
| AT282867B (en) * | 1967-10-11 | 1970-07-10 | Stoll Kg Christof | Seating |
| CA869337A (en) * | 1969-09-23 | 1971-04-27 | Doerner Products Co. Limited | Chair control with support for the torsion spring |
| DE2218941A1 (en) * | 1972-04-19 | 1973-10-31 | Drabert Soehne | DEVICE FOR ADJUSTING THE INCLINE OF THE BACKREST OF A CHAIR |
| GB1430576A (en) * | 1972-05-18 | 1976-03-31 | Evertaut Ltd | Adjustable back rests of chairs |
| FR2491310A1 (en) * | 1980-10-03 | 1982-04-09 | Cannone Vincent | Back rest adjustment for seat - controls height and position and consists of rotary element in two parts receiving sliding arm which supports backrest |
-
1993
- 1993-02-17 CA CA 2089694 patent/CA2089694A1/en not_active Abandoned
- 1993-07-21 WO PCT/CA1993/000300 patent/WO1994002052A1/en active Application Filing
- 1993-07-21 AU AU45561/93A patent/AU4556193A/en not_active Abandoned
Also Published As
| Publication number | Publication date |
|---|---|
| WO1994002052A1 (en) | 1994-02-03 |
| AU4556193A (en) | 1994-02-14 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US5599064A (en) | Swivel rocker | |
| US7234775B2 (en) | Dynamically balanced seat assembly having independently and arcuately movable seat and backrest and method | |
| EP0517206B1 (en) | Chair control mechanism | |
| CA2089695C (en) | Unitary brake for a chair tilt mechanism | |
| US7681952B2 (en) | Chair with tiltable backrest | |
| CA2381880A1 (en) | Chair with swinging back and adjustable height chair arms | |
| US4948198A (en) | Knee-tilt chair control | |
| JPH03109009A (en) | Supporting device for chair capable of inclination | |
| US4013257A (en) | Chair control | |
| EP0263535A2 (en) | Chair with movable seat and backrest | |
| US6588844B1 (en) | Chair wit tiltable seat | |
| US20080111414A1 (en) | Casual control tilt lockout | |
| CA2310549C (en) | Combination worksurface and armrest for a seating unit | |
| US5340194A (en) | Device for adjusting seat frame and back rest of chair of swivel type chair | |
| KR100829322B1 (en) | A mobile joint suitable for a sitting device | |
| US7497516B2 (en) | Mobile joint with several stable positions, suitable for use in furniture | |
| US4013258A (en) | Chair control for tiltable chairs | |
| US5382077A (en) | Height adjustment mechanism for a chair seat back | |
| CA2089694A1 (en) | Unitary spring for biasing a chair seat back support mechanism against a seat tilt mechanism | |
| US20050077771A1 (en) | Multi-position headrest and mechanism therefor | |
| US20050194823A1 (en) | Flexible chair with post base | |
| US11122900B2 (en) | Seat module and tilt mechanism | |
| CA1056291A (en) | Chair structure and tilt mechanism therefor | |
| CN115530561B (en) | Self-adaptive seat | |
| JPH0450841Y2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EEER | Examination request | ||
| FZDE | Dead |