Lumbar support adjustment mechanism

Information

  • Patent Grant
  • 6189972
  • Patent Number
    6,189,972
  • Date Filed
    Friday, June 5, 1998
    26 years ago
  • Date Issued
    Tuesday, February 20, 2001
    23 years ago
Abstract
A chair back comprises a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; a lumbar support member positioned between the front and rear surfaces and mounted for vertical movement with respect to the chair back and for forward movement with respect to the front surface; a first control member positioned on the rear surface of the chair back for adjusting the forward movement of the lumbar support member; and, a second control member positioned adjacent one of the sides of the chair back for adjusting the vertical height of the lumbar support member.
Description




FIELD OF THE INVENTION




The present invention relates to an adjustable back or lumbar support for a seat. In particular the present invention relates to a back support having means for adjusting both the amount of lumbar support and the vertical position of the lumbar support.




BACKGROUND OF THE INVENTION




Lumbar supports exist in various forms to support the lumbar region of the human spine. Many of these prior art designs include a support which extends outwardly or curves outwardly to produce support against an appropriate position of the back. While prior art designs for adjusting the horizontal position of a lumbar support in this manner are known, these mechanisms typically include a large number of parts and are difficult, time-consuming, and costly to manufacture.




In addition, while a number of designs do provide for the horizontal adjustment of a back support, many of these do not include means for adjusting the vertical position of the support, thus reducing the available range of support positions and the potential for users of different shapes and sizes to use the seat. While prior art designs for adjusting both the horizontal and vertical positions of a lumbar support are known, these mechanisms are again complex and expensive to manufacture. More importantly it is generally desirable to minimize the thickness and size of the seat back, particularly with respect to any horizontal adjustment mechanism; something which complex and intricate lumbar support mechanisms do not generally permit.




For instance, U.S. Pat. No. 4,295,681 to Gregory shows a lumbar support device having two control means; one for adjusting the outward movement of the lumbar support and the other for adjusting the height of the lumbar support. Gregory uses a relatively large and complex mechanism consisting of a pair of link members and trunnions located on a threaded adjustment nut, one of which is on a shaft having a right hand thread, and the other is on a shaft having a left hand thread.




In Barley, U.S. Pat. No. 4,313,637, the lumbar support mechanism is positioned between spaced pairs of support arms. The respective arms of each pair are connected to define levers which adjust the amount of lumbar support which is provided.




Zacharkow, in U.S. Pat. No. 4,981,325, discloses a chair back having an upper back support member and a lower back support member. The lumbar support mechanism uses arms that extend from a threaded rod and are pivotally connected to the cushion which provides the lumbar support. The means for controlling the tilt of the lumbar support cushion is provided between the end of the arm and the cushion.




Sessini, U.S. Pat. Nos. 5,335,965 and 5,567,011, discloses a horizontally and vertically adjustable lumbar support device which utilizes a curved elastic plate and two vertically disposed threaded rods. The distal end of each rod in non-rotatably connected to one end of the curved elastic plate while the inner end of each rod is threadedly received in cylindrical scroll. The control is positioned an the side of the seat back and is connected to the lumbar support by multiple linkages. The support is adjusted vertically on a pair of vertical guides by means of control mechanism which includes a cord.




All of these support mechanisms require relatively large and complex mechanisms to enable adjustment of the amount of lumbar support which is provided by the device. Simplicity, reliability, and durability of design are also especially important since the lumbar adjustment mechanisms are generally located, for the most part, inside the upholstered seat back of the chair, and repairs are often difficult if not impossible to make.




Sheldon, U.S. Pat. No. 4,730,871, discloses a device which includes a vertical track and a guide made of spring steel which is mounted to be movable up and down in the track. The guide has a central portion spaced from the track to which the lumbar support member is attached. A screw member extends through the track to the lumbar support member. Rotation of the screw member allows the lumbar support member to be loosened to move vertically in the track and also causes the lumbar support member to be drawn rearwardly or pushed forwardly. While Sheldon discloses a simpler device, one problem with this mechanism is that a single control is used to adjust the vertical and horizontal adjustment of the lumbar support. Thus, the setting of the position and the amount of lumbar support are not independent. For example, when adjusting the height of the lumbar support, the amount of lumbar support may be affected.




SUMMARY OF THE INVENTION




In accordance with the instant invention, there is provided a chair back comprising a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; a lumbar support member positioned between the front and rear surfaces and mounted for vertical movement with respect to the chair back and for forward movement with respect to the front surface; a first control member positioned on the rear surface of the chair back for adjusting the forward movement of the lumbar support member; and, a second control member positioned adjacent one of the sides of the chair back for adjusting the vertical height of the lumbar support member.




One advantage of the instant invention is that by providing independent controls for the height adjustment and the amount of support provided by the lumbar support member, the controls and their positioning may be simplified. For example, it is difficult to quickly and correctly position the height of the lumbar support member while not seated in a chair. By positioning the height adjustment control on the side of the back rest, the user may easily adjust the height of the lumbar support member to suit their physiology.




Further, by providing a control on each side of the chair back, the control mechanism may be easily actuated by both right handed and left handed individuals.




By positioning the control to adjust the amount of support provided by the lumbar support in the center of the back rest, the control mechanism may be simplified, thus simplifying the manufacture of the device and, by reducing the number of linkages involved, increasing its reliability.




In one embodiment, a second control member may be positioned adjacent each side of the chair back.




In another embodiment, the side has a longitudinally extending opening and the second control member extends through the opening to the lumbar support member and travels along the opening as the height of the lumbar support member is adjusted.




In another embodiment, the lumbar support member is mounted on a track and is longitudinally moveable thereon to adjust the position of the lumbar support member with respect to the chair back. The track has first engagement members and the lumbar support member has a second engagement member which releasably engages the first engagement members as the lumbar support member moves longitudinally along the track.




In another embodiment, the lumbar support member is mounted on a track and is longitudinally moveable thereon to adjust the position of the lumbar support member with respect to the chair back and the lumbar support member has a second engagement member which frictionally engages the track to releasably engage the track as the lumbar support member moves longitudinally along the track.




In another embodiment, the lumbar support member is mounted on a track and is longitudinally moveable thereon to adjust the position of the lumbar support member with respect to the chair back. The lumbar support member has a runner which travels in the track and at least a portion of the track has a thickness less than the thickness of the runner to frictionally engage the runner to hold the lumbar support member in position with respect to the chair back.




In another embodiment, the lumbar support member is mounted on a track and is longitudinally moveable thereon to adjust the position of the lumbar support member with respect to the chair back. The lumbar support member has a runner which travels in the track and the track has alternating portions which vary in thickness. A plurality of the portions of the track have a thickness less than the thickness of the runner to frictionally engage the runner to hold the lumbar support member in position with respect to the chair back and a plurality of the portions of the track have a thickness greater than the thickness of the runner to permit the runner to travel freely therein.




In another embodiment, the lumbar support member includes a a compressible member and an adjustable member for applying a compressive force to the compressible member, the compressible member extending forwardly when compressed by the adjustable member.




In another embodiment, the lumbar support member includes a flexible panel and an adjustable member. The flexible panel has an upper end and a lower end and the adjustable member engages the upper and lower ends of the flexible panel and extends rearwardly of the flexible panel whereby the flexible panel bows forwarding when compressed by the adjustable member.




In another embodiment, the lumbar support member includes a flexible panel, a flexible member and a frame member. The flexible panel has an upper end and a lower end and one of the upper and lower ends is mounted to be vertically fixed in position with respect to the frame member. The flexible member contacts the other of the upper and lower ends of the flexible panel and extends rearwardly of the flexible panel whereby the flexible panel bows forwarding when compressed by the flexible member. In this embodiment, the chair back may further comprise a rigid support member and the lumbar support member may further comprise an arm member pivotally mounted on the rigid support member. A first arm of the arm member is connected to the flexible member and a second arm extends to contact the first control member. The first control member includes a member mounted for transverse movement whereby transverse movement of the member in one direction causes the second arm to move transversely and the first arm to move vertically to compress and bow the flexible panel. The first control member may comprise a threaded member rotatably mounted on the rigid support member and a rotatable control knob rotatably mounted on the threaded member.




In another embodiment, the chair back further comprises a rigid support member and the lumbar adjustment member further comprises a threaded shaft rotatably mounted on the rigid support member for movement in the transverse direction about its longitudinal axis, a rotatable knob operable to move the shaft in the transverse direction, a pivoting member pivotally mounted to the rigid support member and having a first arm having a first end which abuts one end of the threaded shaft and a second arm having a first clamping member for receiving the first end of the flexible member, and a second clamping member attached to one of the lower end of the flexible panel and the rigid support member for receiving the second end of the flexible member.




In another embodiment, the lumbar support member comprises a flexible panel having first engagement members and a rigid member having second engagement members; and the chair back further comprises a rigid support member having a plurality of openings, the first and second engagement members passing through the openings to engage and fix the flexible panel in position with respect to the rigid member. In this embodiment, the chair back may further comprise first and second attachment members for fixedly attaching each transverse side of the flexible panel to the respective side of the rigid member the first and second attachment members passing through the openings in the rigid support member whereby the transverse sides of the flexible panel are fixed in position with respect to the rigid member and the portion of the flexible panel between the transverse sides of the flexible panel being free to bow forwardly.




In another embodiment, a height adjustment mechanism for a lumbar support for a seat back comprises a rigid support member for the seat back, the rigid support member having a longitudinally extending track, the lumbar support member mounted on a track and longitudinally moveable thereon to adjust the position of the lumbar support member with respect to the chair back, the track having first engagement members and the lumbar support member having a second engagement member which releasably engages the first engagement members as the lumbar support member moves longitudinally along the track.




In another embodiment, a lumbar adjustment mechanism for mounting in a seat back and adjusting the amount of support provided by a lumbar support comprises a rigid support member; a flexible panel having an upper end and a lower end; a flexible member mounted on the rigid support member and engaging at least one of the upper and lower ends of the flexible panel and extending rearwardly of the flexible panel; and, a tensioning mechanism mounted on the rigid support member whereby adjustment of the tensioning mechanism increases the tension on the flexible member and, as the tension in the flexible member increases, the flexible panel bows forwardly.











BRIEF DESCRIPTION OF THE DRAWINGS




These and other advantages of the instant invention will be more fully and completely understood in association with the following description of the preferred embodiment of the invention in which:





FIG. 1

shows a seat or chair having the lumbar support adjustment mechanism of the present invention integrated therein;





FIG. 2

shows an exploded view of the lumbar support adjustment mechanism of

FIG. 1

;





FIG. 3

is a back view of the lumbar support adjustment mechanism with the shroud of the back rest of

FIG. 1

removed;





FIG. 4

shows an alternate embodiment of the flexible support member of

FIG. 2

;





FIG. 5

is a sectional view along the lines A—A in

FIG. 3

;





FIG. 6

is a sectional view along the lines B—B in

FIG. 3

;





FIG. 7

shows a detailed view of the tension adjustment mechanism;





FIG. 8

illustrates the vertical adjustment feature of the present invention; and





FIG. 9

illustrates the forward adjustment of the lumbar support member of the present invention.











DETAILED DESCRIPTION OF THE INVENTION





FIG. 1

shows a chair


12


with the adjustable lumbar support mechanism of the present invention integrated therein. The chair


12


comprises a seat portion


14


and a seat back portion


16


, the seat back portion having a back cover


18


. Seat back portion


16


may be of any shape or configuration known in the art.




Chair


12


may be a seating unit of any general type, shape or configuration. As shown in the preferred embodiment, chair


12


is an office chair or a task chair where a person may be seated for an extended period of time while working.




Seat portion


14


may be mounted on a support member


15


for supporting seat portion


14


at an elevated height. Preferably, the support member


15


comprises a longitudinally extending cylinder


15




a


(which, more preferably, is a pneumatic cylinder) having a wheeled base


15




b


as shown in FIG.


1


.




The lumbar support mechanism forms part of the seat back portion


16


and, as explained in detail below, may be independently adjusted in both the horizontal direction (via control


82


) and the vertical direction (via control


67


) as indicated by the double-headed arrows in FIG.


1


. The term vertical is used herein as a general direction reference and not an absolute term and is intended to be understood with reference to the plane passing upwardly through seat back portion


16


. The term horizontal is used herein as a general direction reference and not an absolute term and is intended to be understood with reference to the plane transverse to the plane passing upwardly through seat back portion


16


.




In one preferred embodiment, the lumbar support includes a mechanism to increase or decrease the amount of lumbar support which is provided. To this end, a flexible support


20


which expends outwardly under compression is provided. In another preferred embodiment, the lumbar support alternately includes, or may in addition include, a height adjustment mechanism. To this end, seat back


16


may be provided with a frame


30


having a track for vertical travel of the lumbar support device with respect to seat back


16


.





FIG. 2

shows a detailed exploded view of the adjustable lumbar support mechanism


10


of the invention which includes both adjustment means while

FIG. 3

shows a detailed view of the rear of mechanism


10


. The mechanism


10


comprises a flexible support member


20


mounted on a rigid support frame


22


. If the lumbar support includes a height adjustment mechanism, then, as explained more fully below, the flexible support


20


is attached to the support frame


22


with the rigid seat back frame


30


(not shown in

FIG. 3

) of the seat back disposed therebetween.




The exact shape or form of the seat back frame


30


is not dictated by the invention, and may be on any typically rectangular shape or other shape suitable to accommodate the seat back of a chair. Thus, the lumbar support of this invention may be adapted for use with any conventional chair back.




The frames


22


and


30


are preferably made of metal or some other durable, rigid material. For example, frame


22


may be made from plastic and frame


30


may be made from a composite wood material. The flexible support


20


is of a resilient material which will expand outwardly when compressed and, when the compressive force is removed, will at least substantially resume its original shape. Preferably, flexible support


20


is a planar member which is composed of a suitably resilient material such as sheet metal, a plastic or the like so that it may be repeatedly bent without any significant lose of flexibility and also without cracking or otherwise suffering fatigue damage. Preferably, support


20


also has a number of support fingers


24


which extend transversely from the sides


26


of the support


20


. The support fingers


24


may be shaped to better accommodate the shape of a human back, as is known in the art. As shown in

FIG. 4

, the flexible support


20


may also comprise one or more holes or gaps


25


centered about the vertical median of the support so as to improve the support's flexibility in the longitudinal direction.




With reference to

FIG. 2

, within the seat back frame


30


are a plurality of aligned channels and, preferably, a plurality of pairs of upper and lower vertically extending channels. These channels are openings in seat back frame


30


that are sized and positioned to permit flexible support


20


and rigid frame


22


to move together upwardly or downwardly with respect to seat back frame


30


.




Pursuant to the height adjustment mechanism of the preferred embodiment of the invention, frictional engagement may be used to hold the lumbar support at various heights. Accordingly, the track may have first engagement members and the support frame


22


and/or the flexible member


20


may have a second engagement member which releasably engages the first engagement members as the lumbar support member moves longitudinally along the track. The frictional engagement may be provided by an abutment surface provided on the inside of one or more of the channels and/or by an abutment surface provided on the front or the rear face of seat back frame


30


. The frictional engagement may be continuous, to permit the infinite adjustment of the lumbar support within the channels, or intermittent, to define a series of preset positions.




For example, in the preferred embodiment shown in the drawings, there is provided a pair of upper vertical aligned channels


32


and


34


and a pair of lower vertical aligned channels


36


and


38


. The transverse width of the upper vertical channels


32


and


34


varies between a certain minimum width


64


and a certain maximum width


62


(see

FIG. 3

) so as to define alternating portions which vary in thickness. The lower channels


36


and


38


may be generally rectangular and may have a fixed transverse width. The seat back frame


30


also contains two other gaps or recesses (or channels)


42


and


44


. Gap


42


may be located in the upper median portion of the frame


30


, whereas gap


44


may be located in the lower median portion of the frame


30


and vertically aligned with the lower vertical channels


36


and


38


.




The support frame


22


may be of any particular shape as long as it provides a rigid support on which flexible support


20


may be mounted. Preferably, as shown in

FIGS. 2 and 3

, support frame


22


has a U-shape, with a lower base portion


50


and two side portions


52


.




Flexible support


20


is mounted on frame


22


to be moveable therewith while still being compressible to bow outwardly. It will be appreciated that at least the top or the bottom of flexible support


20


must be vertically compressible with respect to frame


22


for the amount of lumbar support provided by flexible support


20


to be adjustable. It will also be appreciated that both the top and the bottom of flexible support


20


may be compressible with respect to frame


22


.




As shown in

FIG. 2

, support frame


22


may include forward projecting appendages


63


having hooks


65


for receiving and supporting the slotted out portions


23


at the sides of the bottom end of the flexible support member


20


. As hooks


65


are not physically attached to flexible support


20


, the lower portion of flexible support


20


may move upwardly to an extend with respect to hooks


65


. It will be appreciated that, in an alternate embodiment, the lower portion of flexible support


20


may be affixed to frame


22


in a variety of different manners and may be fixedly attached thereto, eg. by means of screws, glue and the like.




Cable


70


engages the upper portion of flexible support


20


and, due to the tension in cable


70


, maintains the upper portion of flexible support


20


in place with respect to frame


30


while leaving flexible support


20


free to bow outwardly when the tension of cable


70


is increased. It will also be appreciated that the upper portion of flexible support may be affixed to frame


22


and that the lower portion may be maintained in place with respect to frame


30


while leaving flexible support free to bow outwardly.




The sides


26


of the flexible support member


20


may be fixed to the top ends


54


of side portions


52


of the support frame


22


means, for example, of anchoring devices


58


(see FIGS.


2


-


6


). The anchoring devices may pass, for example, through the narrow vertical portion


55


which abut the top ends


54


(see FIG.


2


). Alternately, anchoring devices


58


may be positioned at any location whereby they pass through a channel in frame


30


so that they will not hinder the vertical movement of flexible member


20


. Anchoring devices


58


may comprise screws, but other means for fastening the support


20


to the support frame


22


may also be used. It will be appreciated that by affixing sides


26


to support frame


22


, only the central portion of flexible support


20


will bow outwardly to provide lumbar support. If desired, sides


26


may remain unaffixed to support frame


22


thus allowing the sides


26


to bow outwardly with the central portion of flexible support


20


so as to provide a transversely extending lumbar support across the entire width of flexible member


20


. It will also be appreciated that a narrow flexible support


20


may be provided to provide only a narrow flexing lumbar support surface thus avoiding the need for anchoring devices


58


.




Height adjustment bar


56


comprises a transversely extending member having opposed sides


66


and


68


. The sides


66


and


68


extend outwardly from the sides of the seat back portion


16


as illustrated in FIG.


1


and have a handle


67


or other type of manipulation means attached to their ends to facilitate the application of force by a user. Height adjustment bar


56


is affixed to frame


22


. For example, the top ends


54


of the side portions


52


of frame


22


may be thicker than the remainder of the side portions and also include a gap (not shown) through which horizontal height adjustment bar


56


is fitted, as illustrated in FIG.


2


. The top ends


54


may also be somewhat wider in the transverse direction than the remainder of side portions


52


, as best seen in FIG.


3


.




In the preferred embodiment, the frictional engagement is provided by runners positioned in the channels in frame


30


. Engagement members


60


, which may be cylindrical plugs or other suitable devices, are inserted, for example, through the top ends


54


of the support frame


22


and through horizontal height adjustment bar


56


into the vertical channels


32


and


34


respectively to act as runners in the channels. Referring to

FIG. 3

, engagement members


60


are of a size and shape (preferably cylindrical) such that they move freely within portions


62


of the vertical channels


32


and


34


having a relatively larger width and they are statically immoveable within portions


64


of the vertical channels


32


and


34


having a relatively smaller width to define a series of preset positions. The term statically immoveable is intended to indicate that the engagement members


60


will not move until a force at or above a certain threshold has been applied to them. This prevents the lumbar support from being accidentally moved once the user places the lumbar support in a desired position.




It will be appreciated that height adjustment bar need not be horizontal but may be of any particular configuration that can transmit a vertical (i.e. upward or downward) force from a position adjacent the side of seat back


16


to frame


22


.




Thus the height of the flexible support member


20


, which is mounted on support frame


22


, may be adjusted by applying a sufficient amount of force either upwardly or downwardly at one handle


67


on one of the sides


66


and


68


of the horizontal height adjustment bar


56


. The engagement members may thereby be moved from one portion of the channels


32


and


34


in which they are statically immoveable to another portion in which they are also statically immoveable. Referring to

FIG. 2

, as the engagement members


60


travel up and down the vertical channels


32


and


34


, the forward projecting appendages


62


at the sides of the base portion


50


of the support frame


22


simultaneously and correspondingly travel up and down the vertical channels


36


and


38


in the seat back frame


30


.




Channels


32


,


34


,


36


and


38


define a vertical track along which flexible support


20


may travel. Each channel is positioned to provide a track adjacent one of the corners of flexible support


20


thereby preventing, or minimizing, transverse motion of flexible member


20


as it travels upwardly or downwardly. It should be noted that although a preferred embodiment of the present invention uses an upper pair of channels (


32


and


34


) and a lower pair of channels (


36


and


38


), a differing or the same number of channels positioned at differing or the same locations may be used.




It will be appreciated that narrow portions


55


may be provided to act as stops to engage the upper and lower surfaces of the channels. In another embodiment, engagement members


60


may act as the stops.




An advantage of the instant invention is that the height adjustment of the lumbar support may be easily actuated while the user is seated in the chair. By mounting frame


22


so that it rides on a track (eg. The channels), the user need only grasp one handle


67


to apply the requisite force to height adjustment bar


56


to adjust the height of the lumbar support. It will be appreciated that height adjustment bar may only extend transversely outwardly of one side of seat back


16


. However, it is preferred that adjustment bar extends transversely outwardly of both sides of seat back


16


so that the height of the lumbar support may be easily adjusted by both a right handed and a left handed person.




The amount of lumbar support provided by flexible support


20


is adjusted by applying a compressive force to the upper and lower portions of flexible support


20


. In the preferred embodiment, the compressive force is provided by a cable or other tension element


70


having a first end


70




a


and a second end


70




b.


Cable


70


engages the upper and lower ends of the flexible support


20


and extends either along the rear surface


27


of flexible support


20


(eg. when the flexible support is in the relaxed, flat state as shown in

FIG. 6

) or rearwardly of the flexible support (eg. when flexible support is under tension as is shown in

FIG. 9

) whereby the flexible support bows forwarding in the direction of the arrow shown in

FIG. 9

when compressed by cable


70


.




As best illustrated in the cross-sectional view of

FIG. 6

, the median portion of the top edge of the flexible support


20


has a bearing member


74


which has an opening so that cable


70


may pass freely therethrough. Similarly, the median portion of the bottom edge of the flexible support


20


has a bearing member


76


which has an opening so that cable


70


may pass freely therethrough.




The cable


70


and bearing members


74


and


76


respectively, pass through the holes or gaps


42


and


44


in the seat back frame


30


which are vertically elongated as shown in

FIG. 2

to accommodate variations in the height of the flexible support member


20


. By increasing the tension of the cable or tension element


70


, flexible support


20


is compressed and the vertically extending median portion of the flexible support member is arched or bowed forwardly (i.e. convexly) to provide lumbar support at varying horizontal positions and independently of height adjustment. As will be appreciated, cable


70


is preferably affixed to frame


30


so that the ends of cable


70


do not travel when flexible support


20


is adjusted vertically. Since cable


70


is free floating on bearing members


74


and


76


, the forward bowing of flexible support


20


is not affected by the vertical movement of flexible support


20


. It will be appreciated that cable


70


may be affixed to frame


22


.




The amount of lumbar support may be varied by adjusting the length of cable


70


. As the vertical travel of cable


70


is shortened, a compressive force is applied to the upper and lower portions of flexible support


20


thus causing flexible support to bow outwardly. Cable


70


may be shortened by winding cable


70


onto a spindle or the like. However, in order to reduce the force which must be applied to shorten cable


70


, in the preferred embodiment, the vertical travel is shortened by transversely moving one end of cable


70


.





FIG. 7

best illustrates a preferred embodiment of a means for adjusting the tension of the cable


70


to compress flexible support


20


. A pair of attachment members


84


having openings (not shown) extend rearwardly from frame


30


. A horizontal threaded shaft


80


having an abutment face


88


extends through the openings in attachment members


84


. The openings are sufficiently large that threaded shaft


80


is rotatably mounted on attachment members


84


. A rotatable hand-actuated knob


82


is threadedly mounted to the shaft


80


between attachment members


84


. As hand actuated knob


82


is fixed in position between the pair of attachment members


84


, rotation of knob


82


causes threaded shaft to move transversely. As knob


82


rotates in one direction, causing threaded shaft to rotate about its longitudinal axis, it moves transversely to the left when rotated in one direction and transversely to the right when rotated in the other direction.




Lever


86


is pivotally mounted to seat back frame


30


by any means known in the art. As shown in

FIG. 7

, lever


86


comprises first arm


90


, second arm


92


and a base or fulcrum portion


96


. Fulcrum


96


is pivotally attached to the seat back frame


30


by pivot mount


100


. Arms


90


and


92


of the lever


86


are joined to fulcrum portion


96


of the lever, about which the lever (and the arms) pivot and rotate. Arm


90


has an end


91


distal to fulcrum


96


and arm


92


has an end


93


distal to fulcrum


96


.




Abutment face


88


of the shaft


80


abuts face


91




a


and


91


of first arm


90


. Second arm


92


includes at or near end


93


means


94


for receiving and retaining therein end


70




a


of the cable


70


. End


70




a


may be secured therein by any means known in the art such as by using a set screw or by providing an opening in end


93


through which cable


70


extends and providing end


70




a


with an enlarged stop (not shown).




End


70




b


of the cable


70


is fixedly attached to seat back frame


30


. Therefore, as the position of end


70




a


of cable


70


is adjusted, the effective (or vertical) length of cable


70


is adjusted. End


70




b


may be affixed to seat back frame


30


by any means known in the art. For example, bracket


97


may be mounted to the rear face of seat back frame


30


with a rod


98


extending therebetween. End


70




b


may be provided with a loop through which rod


98


extends.




As shown in

FIGS. 1 and 6

, the back cover


18


of the seat back portion


16


contains a gap or hole through which the hand-actuated knob


82


protrudes for ease of manipulation by a user. In operation, as the knob


82


is rotated, the shaft


80


moves horizontally in a transverse direction. As shown for example in

FIG. 3

, as the shaft moves to the right, this forces the arms


90


and


92


of the lever


86


to rotate in a counter-clockwise direction. Since cable


70


is effectively inelastic, as arm


90


moves to the right, the vertical distance travelled by cable


70


from end


70




b


to end


70




a


decreases. Thus cable


70


applies a compressive force to flexible support


20


. Conversely, as the shaft


80


moves to the left, the arms


90


and


92


rotate about the fulcrum


96


in a clockwise direction and thereby allow the vertical distance travelled by cable


70


to increase. In this manner, the convex curvature of the vertical median of the flexible support member


20


can be adjusted to accommodate the lumbar support requirements of a particular seat user. The greater the rightward displacement of arm


90


, the more bowed or curved is the vertical median of the flexible support member


20


.




The present invention thereby independently provides both vertical adjustment of the support member


20


as illustrated in FIG.


8


and bowing adjustment of the vertical median of the support member as illustrated in FIG.


9


.

FIGS. 3 and 6

respectively illustrate the position of the tension adjustment mechanism and the bowing of the flexible support member


20


and when the cable is under low tension.

FIG. 9

, on the other hand, illustrates the bowing of the vertical median of the flexible support member under a greater amount of tension.




Because the tension adjustment mechanism for cable


70


is fixed with respect to the seat back frame


30


, the tension adjustment mechanism does not change position when the height of the flexible support member


20


is adjusted. This is illustrated in FIG.


8


. Thus, as the height of flexible support


20


is adjusted, cable


70


slides around bearing members


74


and


76


. As a result, it is unnecessary to create and elongated vertical gap in the back cover


18


of the seat back portion of the seat to accommodate for the protrusion of the hand-actuated knob


82


.




Due to the independent nature of the two adjustment mechanisms, it will be appreciated that if the lumbar support in seat back


16


is not height adjustable, frame


30


need not be sandwiched between flexible support


20


and support frame


22


. In fact, in such an embodiment, frame


30


may function as support frame


22


. It will also be appreciated that, in another embodiment, a non-adjustable lumbar support member, or an alternate means of adjusting the amount of lumbar support which is provided by the lumbar support member, may be used in conjunction with the height adjustment member disclosed herein.




While preferred embodiments of the present invention have been described, the embodiments disclosed are illustrative and not restrictive, and the scope of the invention is intended to be defined only by the appended claims.



Claims
  • 1. A chair back for mounting to an office chair having a seat, the chair back comprising:(a) a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; (b) a lumbar support member movably mounted between the front and rear surfaces on a track for vertical movement of said lumbar support member with respect to the chair back and for forward longitudinal movement with respect to the chair back, the lumbar support member has a runner which travels in the track, the track being provided on a frame and having alternating portions which vary in width, a plurality of the portions of the track having a width less than the thickness of the runner to frictionally engage the runner to hold the lumbar support member in position with respect to the chair back and a plurality of the portions of the track having a width greater than the thickness of the runner to permit the runner to travel freely therein; (c) a first control member operatively connected to the lumbar support member for adjusting the forward movement of the lumbar support member; and (d) a second control member operatively connected to the lumbar support member for adjusting the vertical height of the lumbar support member relative to the front surface, the first control member remaining at a fixed position with respect to the rear surface when the vertical height of the lumbar support member is adjusted.
  • 2. A chair back for mounting to an office chair having a seat, the chair back comprising:(a) a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; (b) a lumbar support member movably mounted between the front and rear surfaces of a rigid frame for vertical movement of said lumbar support member with respect to the chair back and for forward movement with respect to the front surface, the lumbar support member comprising a flexible panel, a flexible member, a frame member and an arm member, the flexible panel having an upper end and a lower end, one of the upper and lower ends mounted to be vertically fixed in position with respect to the frame member, the flexible member contacting the other of the upper and lower ends of the flexible panel and extending rearwardly of the flexible panel whereby the flexible bows forwardly when compressed by the flexible member, the arm member having first and second arms, the arm member pivotally mounted on the rigid frame; (c) a first control member drivingly engaging the first arm and the second arm being drivingly connected to the flexible member, the first control member including a lumbar adjustment member mounted for transverse movement whereby transverse movement of the lumbar adjustment member in one direction causes the first arm to move transversely and the second arm to move vertically to compress and bow the flexible panel; and (d) a second control member operatively connected to the lumbar support member for adjusting the vertical height of the lumbar support member.
  • 3. The chair back as claimed in claim 2 wherein the first control member comprises a threaded member rotatably mounted on the rigid support member and a rotatable control knob rotatably mounted on the threaded member.
  • 4. A chair back for mounting to an office chair having a seat, the chair back comprising:(a) a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; (b) a rigid support member; (c) a lumbar support member movably mounted between the front and rear surfaces to a frame for vertical movement of said lumbar support member with respect to the chair back and for forward movement with respect to the front surface, the lumbar support member comprising a flexible panel, a flexible member connected to said flexible panel and a threaded shaft rotatably mounted on the rigid support member for movement in the transverse direction about its longitudinal axis, a rotatable knob operable to move the shaft in the transverse direction, a pivoting member pivotally mounted to the rigid support member and having a first arm having a first end which abuts one end of the threaded shaft and a second arm having a first member for receiving the first end of the flexible member, and the lower end of the flexible panel has a second member for receiving the second end of the flexible member; (d) a first control member operatively connected to the lumbar support member for adjusting the forward movement of the lumbar support member; and, (e) a second control member operatively connected to the lumbar support member for adjusting the vertical height of the lumbar support member.
  • 5. A chair back for mounting to an office chair having a seat, the chair back comprising:(a) a rear surface, a front surface spaced from the rear surface and a side extending between the front and rear surfaces; (b) a lumbar support member movably mounted between the front and rear surfaces to a frame for vertical movement of said lumbar support member with respect to the chair back and for forward movement with respect to the front surface, the lumbar support member comprising a flexible panel having first engagement members and a rigid member having second engagement members, the frame having a plurality of openings, the first and second engagement members passing through the openings to engage and fix the flexible panel in position with respect to the rigid member; (c) a first control member operatively connected to the lumbar support member for adjusting the forward movement of the lumbar support member; and, (d) a second control member operatively connected to the lumbar support member for adjusting the vertical height of the lumbar support member.
  • 6. The chair back as claimed in claim 5 further comprising first and second attachment members for fixedly attaching each transverse side of the flexible panel to the respective side of the rigid member, the first and second attachment members passing through the openings in the frame whereby the transverse sides of the flexible panel are fixed in position with respect to the rigid member and the portion of the flexible panel between the transverse sides of the flexible panel is free to bow forwardly.
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