Patent Publication Number: US-9833075-B2

Title: Chair with adjustable backrest and seat

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to adjustable chairs and in particular such chairs having both an adjustable backrest and an adjustable seat. 
     Adjustable chairs are well known in the furniture industry including chairs wherein both the backrest position and the seat position can be adjusted or moved to make the chair more comfortable for the user. It is also known to provide chairs in which the seat and the backrest move synchronously by way of various synchronizing mechanisms. The synchronizing mechanism is able to change the position of the seat at the same time as the backrest is adjusted. 
     For example, U.S. Pat. No. 5,810,440 which issued on Sep. 22, 1998 to the present applicant describes a chair having a base, a seat, a backrest, a back support and a mechanism which interconnects the seat, back and back support and imparts a predetermined synchronous movement to the seat and back, e.g. rearward tilting of the seat and simultaneous rearward tilting of the back. The chair back has a rotation mechanism for rotatably connecting the chair back to the back support. The rotation is about a rotation axis which passes through the upper body of a person when the person is sitting on the seat and resting against the chair back. The bottom portion of the chair back is guided so that the bottom can move along an arc between a first position and a second position which is forward and lower than the first position. 
     More recent U.S. Pat. No. 6,709,057 to Armin Sander describes an adjustable chair having a backrest that is inclinable with regards to a seat carrier via a backrest carrier. The seat surface can be moved synchronously with the backrest and is supported on the seat carrier via at least one seat link. A coupling link linking the seat and the backrest carrier is provided for synchronization between the movement of the backrest and that of the seat surface. 
     Despite the adjustable chairs that are known in the seating industry, there is still a need for an improved chair that can be easily manufactured while at the same time being quite sturdy and durable. There is provided herein an adjustable chair wherein the pivoting movement of the backrest for the chair differs from the amount of pivoting of the seat. In a particular exemplary embodiment of the chair, the overall tilting mechanism for the backrest and the seat causes the rear end of the seat to move backwards and downwards with respect to the backrest when the seat and backrest are tilted backwardly and simultaneously the bottom edge of the backrest to move downwards and slightly rearwards with respect to the rear edge of the seat, thus reducing the horizontal and vertical gap between the rear end of the seat and the backrest. 
     SUMMARY OF THE INVENTION 
     According to one embodiment of the invention described herein, an adjustable chair comprises a chair base support, a backrest, a backrest support mechanism including at least one backrest arm pivotally connected to the base support and joined to the backrest, and a seat having front and rear regions and a top surface providing a seat surface defined by the front and rear regions. The or each backrest arm has a forward arm section and a rearward arm section extending in opposite directions from a respective backrest pivot point. The or each forward arm section has a first part of a first pivot mechanism located adjacent a front end of the backrest arm and spaced from the backrest pivot point. A first seat support mechanism adjustably connects the front region of the seat to the base support so that the seat can both pivot about a first horizontal axis extending in a transverse direction between the side edges and move in a front to rear direction and vice versa relative to the base support. A second seat support mechanism adjustably connects the rear region of the seat to the base support. This second seat support mechanism includes at least one seat arm having front and rear arm extensions and connected to the base support for pivotal movement about a second horizontal axis extending in the transverse direction and located between opposite front and rear ends of the seat arm. The rear arm extension is pivotally connected to the rear region of the seat at its respective rear end. The or each front arm extension has a first part of a second pivot mechanism for the respective seat arm adjacent the front end of the respective arm and spaced from the second horizontal axis. A toggle arrangement is mounted on the chair base support and operably engages both the front end section of the at least one seat arm and front end section of the at least one back rest arm. The toggle arrangement includes a second part of the first pivot mechanism that cooperates with the first part of the first pivot mechanism to form a complete backrest arm pivot mechanism, which includes a first pivot member spaced a distance D from the backrest pivot point and a second part of the second pivot mechanism that cooperates with the first part of the second pivot mechanism to form a complete seat arm pivot mechanism for the at least one seat arm. The second pivot mechanism includes a second pivot member spaced a distance “d” from the second horizontal axis. This toggle arrangement includes at least one additional pivot mechanism providing a third horizontal pivot axis. The distance d is different than the distance D so that the backrest and the at least one backrest arm pivot different degree amounts during use of the chair than the at least one seat arm. 
     An adjustable chair according to another embodiment of the invention includes a chair base support, a backrest, and a backrest support mechanism including a pair of backrest arms pivotally connected at a respective backrest pivot point to the base support and joined to the backrest. Each backrest arm has a forward arm section extending forwardly from its respective backrest pivot point and the rearward arm section extending rearwards from its respective backrest pivot point. Two toggle devices are each pivotally mounted on the chair base support and each operatively engages a respective one of the forward arm sections. There are also two first pivot mechanisms each pivotally connecting a respective one of the forward arm section to a respective one of the toggle devices. The chair includes a seat having a front, a rear, opposite side edges, and a top surface. A first seat support adjustably connects a front region of the seat to the base support so that the seat can both pivot about a horizontal axis extending in a transverse direction of the seat and move in a front to rear direction and vice versa relative to the base support. Also second seat supports adjustably connect a rear region of the seat to the base support. The second seat support includes two seat arms each having front and rear arm extensions and connected to the base support for pivotal movement about a second horizontal axis extending in the transverse direction and located between opposite front and rear ends of the seat arm. The rear arm extensions are pivotally connected to the rear region of the seat at the respective rear ends. The front arm extensions each have a first part of a second pivot mechanism for the respective seat arm adjacent the front end of the respective arm and spaced from the second horizontal axis. Each toggle device operatively engages the front arm extension of a respective one of the seat arms and includes the second part of the second pivot mechanism that cooperates with the first part of the second pivot mechanism to form a complete arm pivot mechanism for the respective seat arm. This complete mechanism includes a second pivot member spaced a distance d from the second horizontal axis. Each first pivot mechanism includes a first part located on its respective forward arm section and spaced from the respective backrest pivot point and a second part that cooperates with the first part to form a respective one of the first pivot mechanisms, which includes a first pivot member spaced a distance D from the respective backrest pivot point. The distance d is different from the distance D so that the backrest and its backrest arms pivot different degree amounts during use of the chair than the two seat arms. 
     In an exemplary embodiment, each toggle device is formed with two spaced-apart branches each formed with a respective elongate slot with one of the slots being the second part of the respective first pivot mechanism and the other slot being the second part of the respective second pivot mechanism. 
     According to yet another embodiment of the invention, an adjustable chair comprises a chair base support, a backrest, and an arm device for supporting the backrest. The arm device includes at least one backrest arm pivotally connected at a backrest pivot point to the base support and joined to the backrest. The or each backrest arm has a forward arm section extending in a forward direction of the chair and a rearward arm section extending in a rearward direction from its respective backrest pivot point. The or each forward arm section has a first pivot member mounted thereon and spaced a distance D from its backrest pivot point. There is also a seat having a front, a front region, a rear, a rear region, opposite side edges and a top surface providing a seating surface defined by the front and rear regions. A first seat support mechanism adjustably connects the front region of the seat to the base support so that the seat can both pivot about a first horizontal axis extending in a traverse direction between the side edges and move in a front to rear direction and vice versa relative to the base support. The chair also includes at least one seat arm adjustably connecting the rear region of the seat to the base support, the or each seat arm having a front arm extension extending in a forward direction and a rear arm extension extending in a rearward direction both from its respective seat pivot point. The seat arm can pivot about a second horizontal axis extending in a transverse direction relative to the seat. The or each rear arm extension is pivotally connected to the rear region of the seat. The or each front arm extension has a second pivot member spaced from the second horizontal axis by a distance d. At least one toggle device is pivotally mounted on the chair base support. The or each device is formed with an elongate slots arrangement for pivotally engaging the first and second pivot members. The distance d is different than the distance D so that the backrest and the at least one backrest arm pivot different degree amounts during use of the chair than the at least one seat arm. 
     The invention is illustrated and described herein as embodied in an office chair. The invention is not intended to be limited to the details shown, since various modifications and structural changes may be made to the chair without departing from the scope of the invention. Further features, advantages and aspects of the chair will be best understood from the following detailed description of specific embodiments in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an office chair constructed in accordance with the invention and shown in an upright position, this view being taken from above and from the front of the chair; 
         FIG. 2  is a detail view in perspective showing the seat support mechanism for a front region of the chair seat and front portions of both seat and backrest support arms, this view being taken in the direction of arrow  2  in  FIG. 1 ; 
         FIG. 3  is another detail view taken from below as indicated by the arrow  3  in  FIG. 2 , this view showing the front portions of the seat and backrest arms; 
         FIG. 4  is a schematic side view of the office chair shown in an upright position, the bottom base of the chair being omitted for ease of illustration; 
         FIG. 5  is another schematic side view of the office chair of  FIG. 4 , this view showing a second, inclined position for the backrest and seat; 
         FIG. 6  is a schematic side view of an alternate version of the chair in the upright position; 
         FIG. 7  is a schematic side view of an alternate chair construction, the chair being shown in an upright position; 
         FIG. 8  is an exploded schematic detail view showing the toggle arrangement used in the chair of  FIGS. 1 to 4 ; 
         FIG. 9  is an exploded schematic detail view of another form of toggle arrangement for the seat and backrest support arms; 
         FIG. 10  is another exploded detail view similar to  FIG. 9  but showing a further toggle arrangement for the seat and backrest support arms; and 
         FIG. 11  is yet another exploded detail view showing another toggle arrangement for the support arms. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
       FIGS. 1 and 4  illustrate an office chair  10  having a standard base  11  which has been omitted from  FIG. 4  for ease of illustration. This standard base can, for example, include a central support cylinder  17  with a vertical axis which receives the illustrated post  12 . Four or five spokes or legs can extend radially outwardly from this cylinder or sleeve and are rigidly connected thereto. The spokes or legs can be supported on well known casters (not shown) so that the chair can be readily moved on a floor surface. The illustrated upper portion of the chair includes a backrest  13  and a seat  14  having a front  16  and a rear  18 . By way of further explanation, the seat also has a front region  20  and a rear region  22  which together form the overall seat. The seat has a top surface  24  that provides a seating surface for a person and that is defined by the front and rear regions. The top surface  24  can be contoured as desired to make it comfortable for the user. 
     Located below the seat is a chair base support indicated generally by reference  26  and this base support can be rigidly connected to the top of the post  12 . Alternatively there can be more than one post or leg supporting the base support. If desired, the base support and the attached operating mechanism to be described can be enclosed in a suitably attractive enclosure or housing (not shown). 
     The backrest  13  is mounted on a backrest support mechanism indicated generally at  30  which can include a pair of backrest arms  32 ,  34  pivotally connected to the base support at A 1 . Each backrest arm has a forward arm section  35 , which is clearly shown in  FIGS. 2 and 3 , and a rearward arm section  36 , these two arm sections extending in opposite directions from the respective backrest pivot point located at A 1 . Each forward arm section  35  has a first pivot member located adjacent a front end of the respective backrest arm and spaced a distance D from the respective backrest pivot point A 1 . An exemplary form of the first pivot member comprises a roller  40  rotatably mounted on a support pin extending from the front section of the backrest arm. Each roller moves in a slot  42  formed in one of two toggle members  44 . The two toggle members form a toggle arrangement that is pivotally mounted on the chair base support  26 . The toggle member  44  shown in  FIG. 2  is able to pivot about a pivot pin  46  located at the forward end of the toggle member. 
     The chair  10  also includes a first seat support mechanism  50  that adjustably connects the front region  20  of the seat to the base support  26  in a manner that permits the seat to pivot about a first horizontal axis provided by a further pivot pin  52 , this axis extending in a transverse direction between side edges  54  and  56  of the seat. The pivot pin  52  is mounted in the base support  26 . Furthermore this first seat support mechanism  50  also allows the seat to pivot about the pin  52  and to move in a front to rear direction and vice versa relative to the base support  26  (as seen from a comparison of  FIGS. 4 and 5 ). In the embodiment of  FIGS. 1 to 4  a slightly curved slot  60  is slidable along the pivot pin  52 . The slot  60  is formed in a downwardly extending connecting plate  62  rigidly attached to the bottom of the seat  14 . In an exemplary version of the chair, the two slotted plates  62  are mounted adjacent opposite side edges of the seat but it is also possible to mount them closer to the transverse center of the seat on opposite sides of this center. 
     The seat  14  is also supported by a second seat support mechanism  64  which adjustably connects the rear region  22  of the seat to the base support  26 . The second seat support mechanism includes two seat arms  66 ,  68  each having a front arm extension  70  and a rear arm extension  72  and connected to the base support  26  for pivotal movement about a second horizontal axis which can be located at A 1  or a suitable pivot axis A 2  offset from the axis A 1 . This second horizontal axis also extends in the transverse direction like the first axis and it is located between opposite front and rear ends of each seat arm. The chair illustrated in  FIG. 7  is constructed so that the pivot axis A 2  is spaced below and slightly rearwards of the axis A 1 . The rear arm extensions are pivotally connected to the rear region of the seat at their respective rear ends such as by means of a pivot pin  74  mounted in the frame of the seat. Each front arm extension has an arm pivot member adjacent the front end of the respective arm and spaced a distance d from the second horizontal axis (see  FIG. 3 ). Again, in an exemplary embodiment, this arm pivot member comprises a roller  75 , such as a hard plastic roller, mounted on a pivot pin. Plastic rollers are preferred on both the backrest arms and the seat arms to allow for quiet operation of the tilting mechanism. It is also possible to construct these rollers from metal. Alternatively, it is possible to omit the use of a roller entirely on each seat arm and each backrest arm and to use a metal pivot pin or similar member to engage the respective toggle member  44 . 
     Either a single wide slot or two adjacent slots  42  can be formed in each toggle member to receive the respective rollers mounted at the front ends of the backrest arm and the seat arm.  FIG. 8  illustrates schematically the use of two slots  42  in the toggle member. The slot or slots have a width which closely corresponds to that of the roller or rollers that are movable in the slot. The present chair  10  can be biased towards the upright position shown in  FIGS. 1, 4, 6 and 7  by any of several different forms of known biasing mechanisms. The biasing mechanism can for example include a metal or elastomeric torsion spring mounted around the pivot pin at A 1  or A 2  and having one end engaging either the adjacent backrest arm  32  or the adjacent seat arm and the other end engaged in the chair base support  26  through known tensioning mechanism. A compression metal or elastomeric band can also be used as a biasing mechanism, if desired. 
     Operation of the Exemplary Chair 
     From the above description of the chair  10 , it will be readily seen that when a user is sitting in the upright position shown in  FIG. 4 , he is able to tilt the chair backwards to the position shown in  FIG. 5  by pressing against the backrest  13  and overcoming the biasing force of the biasing mechanism. At the same time as the backrest is tilted rearwardly the seat  14  pivots downwards at its back edge  18  or, in other words, in the clockwise direction as the chair is shown in  FIGS. 1 and 4 . This tilting motion causes the front arm extension  70  of the seat arm to rotate or pivot upwards (that is in the clockwise direction as the chair is illustrated in  FIGS. 4 and 5 ). This pivotal movement of the two seat arms causes the two toggle members  44  to pivot upwardly from the position shown in  FIG. 4  to that shown in  FIG. 5 , that is, in a counterclockwise direction around the pivot pin  46 . This pivotal movement of the two toggle members moves the forward arm sections  34  of the two backrest arms upwards (in the clockwise direction about the pivot axis for the arms  32 ). Thus in a synchronous manner, the pivoting and moving of the seat  14  causes a backward tilting of the backrest  13 . While this is occurring the slot  60  moves rearwards relative to the pin  52 . In this way, the seat moves rearwards and slightly downwards at its front end and rearwards and downwards at its rear end. 
     In a particular exemplary embodiment of the chair  10 , the lengths of the front arm sections  70  and forward arms section  35  are different, which results in a variation in the pivotal movement between the seat  14  and the backrest  13 . In the exemplary embodiment, for approximately every 10 degrees of rotation of the two seat arms  66 ,  68  the backrest arms  32 ,  34  pivot approximately 9 degrees. It will be understood that the length of the front arm extension  70  and the forward arm sections  35  can be set or adjusted to obtain the desired difference in the pivotal movement of the seat and the backrest. In the exemplary embodiment where the front end of the seat is sliding effectively backwards and very slightly downwards, the resulting motion is that the angle of tilt of the backrest changes at a faster rate than the seat angle. It will be understood that for each tilt angle of the backrest  13  there is a corresponding, specific seat angle. 
     To explain the chair movement further, as the chair is tilted backwards, the rear end  18  of the seat moves downwards and backwards and the bottom end of the backrest moves downwards and also backwards. The result is that as the chair is tilted backwards, the rear edge of the seat moves backwards at a faster rate than the bottom edge of the backrest. Also, the bottom edge of the backrest moves downwards at a faster rate than the rear edge of the seat. The net effect is that when the chair is tilted, it reduces the horizontal and vertical gap between the rear end of the seat and the backrest. 
     Thus the present chair tilting mechanism is set up to provide a differential movement between the pivoting motion of the seat and the pivoting motion of the backrest. The reverse is also true when the chair is allowed to move from the tilted position to the upright position. Although the illustrated exemplary embodiment is constructed so that the front end arm sections  70  are shorter than the forward arm sections  35  of the backrest support mechanism, the reverse arrangement is also possible so that the front arm extensions  70  are longer than the forward arm sections  35  and the latter arrangement will also give differential synchronous movement between the seat and the backrest. 
     Although the pivot pins for the seat arms  66 ,  68  and for the backrest arms  32  are shown at the same A 1  location in  FIGS. 2 to 4 , this is not essential for the present mechanism and in fact the pivot pins for the seat arms can be displaced and not in alignment with the pivot pins for the backrest arms  32 . If desired, the pivot pins for the seat arms can be located above, below, forward, or aft of the horizontal axis for the backrest arms  32 . 
     An alternate construction for the first seat support mechanism is illustrated in  FIG. 6 . This first seat support mechanism is indicated at  82 . The mechanism  82  again adjustably connects the front region  20  of the seat to the base support  26  so that the seat  14  can both pivot about a first horizontal axis extending in the transverse direction and also move in a front to rear direction and vice versa relative to the base support. The seat support mechanism  82  includes two relatively short links  84  which are spaced apart and operate in a similar manner. The links are pivotally connected at both ends with their bottom ends connected by pivot pins  86  to the base support. The top ends of the links are connected by pivot pins  88  to a bracket or angle member  90  attached to the front region of the seat. 
     The chair illustrated in  FIG. 7  employs a different form of toggle arrangement indicated generally at  100 , this arrangement again being mounted on the chair base support and operatively engaging both front end sections of the two seat arms  66 ,  68  and front end sections of the backrest arms  32 ,  34 . The toggle arrangement  100  comprises two toggle members  102  which can be constructed in the manner illustrated schematically in  FIG. 9 . The toggle member  102  has a single forward section  104  with an elongate slot  106  formed therein. The forward section is rigidly connected to a U-shaped rearward section  108  having two spaced-apart branches  110  and  112 . A round hole  114  is centrally located in the branch  110  and is sized to receive and pivotally support the pivot pin  75  provided on the forward end of front arm extension  70 . The pivot pin  75  is located a distance d from the seat arm pivot axis located at  120 . It will be understood that the pivot axis at  120  can correspond to the aforementioned pivot axis A 1  or A 2 . Formed in the branch  112  is an elongate slot  122  extending in the longitudinal direction of the branch. The roller  40  at the front end of the forward arm extension  35  is arranged in the slot  122  and the slot is able to move relative to the roller. The axis of the roller  40  is located the distance D from the horizontal pivot axis located at  126  which may or may not be aligned with the pivot axis at  120 . The pivot pin  46  which is mounted on the base support  26  extends into the slot  106 . It will thus be appreciated that each toggle member  102  is able to pivot about the axis at pivot pin  46  and is also able to move in the longitudinal direction along the pivot pin. The toggle arrangement  100  can synchronize the tilting movement of the backrest support with the movement of the chair seat in a manner similar to the toggle arrangement of  FIG. 8 . Again, by making the distance d different from the distance D, the backrest and its backrest arms will pivot a different amount during use of the chair than the two seat arms. 
     A similar but different toggle arrangement  130  is illustrated in  FIG. 10  which shows schematically a toggle member  130 . Like the toggle member  102  of  FIG. 9 , this toggle member has a forward section  132  with a slot  134  formed therein. This toggle member also has two branches  140  and  142  that are part of a U-shaped rearward section. In this embodiment, the elongate slot  144  is formed in the branch  140  while the circular hole  146  is formed in the branch  142 . The pivot pin  40  or roller is provided on the forward end of each forward arm section  35  and is pivotally connected to the branch  142  by extending into the hole  146 . The roller or pivot pin  75  is provided at the forward end of the front arm extension  70  and extends into the slot  144  for movement relative to the slot. It will be appreciated that the two toggle members  130 , only one of which is shown in  FIG. 10 , together form a toggle arrangement which operates in an analogous manner as the toggle arrangement  100 . Again, by making the distance d different than the distance D, the backrest and its backrest arms pivot a different amount during the use of the chair than the two seat arms providing a desirable synchronous action between the backrest and the seat. 
     Another toggle arrangement is illustrated schematically by  FIG. 11  which shows a toggle member  150 . Again there are two of these toggle members provided on each chair, one on each of the opposite sides of the chair. This toggle member has a forward section  152  which can be provided with a circular hole  154  to accommodate a pivot pin (similar to the pivot pin  46  shown in  FIGS. 2, 3, 4, 5 and 7 ). The rearward section of the toggle again has two branches  156 ,  158  and rotatably mounted on each of these branches is a suitable roller  160 ,  161 . The two illustrated rollers are located on the inner surface of each branch but it is also possible to mount them on the outer surface of each branch. The roller  160  is mounted a distance Z 1  from the center of the hole  154  while the roller  161  is mounted a distance Z 2  from the center of the hole  154 . By making the distances Z 1  and Z 2  different, the amount by which the backrest arms pivot will vary relative to the amount of tilting of the two seat arms. Thus the distances Z 1  and Z 2  have a similar effect on the pivoting motion of the backrest and the seat as the distances d and D of the other embodiments. In the front end section of the front arm extension  70  is an elongate slot  162  while formed in the front end section of the forward arm section  35  is another slot  164 . The roller  160  on the branch  156  is mounted in the slot  162  while the other roller  161  is mounted in the slot  164  and these rollers can move back and forth in their respective slots and there can be relative pivotal movement between the slots and their rollers. This alternative toggle arrangement can also provide a desirable synchronous movement between the tilting of the backrest and the movement of the seat. Various combination of the toggles are also possible such that either a slot or pin is used in the front extension of the seat or back arm, to engage either a pin or slot respectively in the forked rear end of the toggle. 
     It will be appreciated that the present chair can come with optional or additional features that are well known in the chair art. For example the backrest  13  can be flexibly attached to the seat  14 , such as by a flexible cloth or leather strip extending between the rear end  18  of the seat and the bottom edge  80  of the backrest. It is possible to provide a seat  14  with a seat depth adjustment capability using known adjustment mechanisms. It is also possible to provide back height adjustment if required in addition to lumbar adjustment by known adjustment mechanisms. 
     With respect to the biasing mechanism to return the chair to the upright position, it is well known to make these biasing mechanisms adjustable, for example by increasing or decreasing the tension in the mechanism. Various mechanisms are also known in the chair art for adjusting the height of the seat, for example by allowing adjustment of the height of the post  12  relative to the column or sleeve in which the post fits. 
     While the present invention has been illustrated and described as embodied in several different exemplary embodiments, that is embodiments having particularly utility as chairs, it is to be understood that the present invention is not limited to the details shown here, since it will understand that various omissions, modifications, and changes in the forms and details of the disclosed chair and its operation may be made by those skilled in the art without departing in any way from the scope of the present invention.