Patent Publication Number: US-9883746-B2

Title: Chair with seat and backrest movable in a synchronized way

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 14/937,615, filed on Nov. 10, 2015, which claims priority to Italian Patent Application No. TO2014A000936, filed on Nov. 11, 2014, the contents of each application are herein incorporated by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a chair with seat and backrest movable in a synchronized way. 
     More precisely, the invention relates to a chair in which the seat is movable between a lowered position and a raised position and the backrest is movable between an upright position corresponding to the lowered position of the seat and a backward-inclined position corresponding to the raised position of the seat. 
     In seats of this type, the resistance opposed by the backrest against the movement of backward inclination is proportional to the weight of the user. Mechanisms of this type are usually known as “weight-activated”. 
     Description of Prior Art 
     One of the first “weight-activated” mechanisms is described in the document EP-A-0249584 by the same Applicant, which describes a chair in which the seat is connected to the support structure by means of at least one parallelogram mechanism comprising two rods whose ends are articulated to the seat and to the support structure, so as to allow a movement of the seat between a lowered position and a raised position. The backrest has a support structure which oscillates between an upright position, corresponding to the lowered position of the seat, and a backward-inclined position, corresponding to the raised position of the seat. The support structure of the seat is rigidly connected to one of the rods of the parallelogram mechanism. The parallelogram mechanism is equipped with elastic elements to push the backrest towards its upright position. 
     The main drawback of chairs equipped with parallelogram mechanisms with articulated rods is the high complexity due to the high number of components. 
     WO2009/039231 (Herman Miller, Inc.) describes a chair with a deformable seat and backrest, which adapts to the user&#39;s weight. This chair comprises two side profiles between which a flexible material is stretched, forming the support surfaces of the seat and the backrest. Each of the two side profiles is formed of an integral element of plastic material with two beam elements connected together by means of integral connecting elements. 
     This chair structure is specifically dedicated to chairs in which the support surface of the seat and the backrest is formed by a flexible sheet and is not easily adaptable to chairs with different configurations of the seat and backrest. 
     SUMMARY OF THE INVENTION 
     The present invention aims to provide a chair with seat and backrest movable in a synchronized way having a simple structure and easily adaptable to different configurations of the seat and backrest. 
     According to the present invention, this scope is achieved by a chair having the characteristics forming the subject of claim  1 . 
     The claims form an integral part of the disclosure provided here in relation to the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in detail, with reference to the attached drawings, given purely by way of non-limiting example, wherein: 
         FIG. 1  is a perspective view of a chair according to the present invention. 
         FIG. 2  is an exploded perspective view of the chair of  FIG. 1 . 
         FIG. 3  is a side view of the element indicated by the arrow III in  FIG. 2 . 
         FIG. 4  is a side view illustrating the chair of  FIG. 1  in a rest position. 
         FIG. 5  is a side view analogous to  FIG. 4  illustrating the chair in the position of maximum backward inclination of the backrest. 
         FIGS. 6 and 7  are cross-sections according to the line VI-VI of  FIG. 1 , in the rest position and in the position of maximum backward inclination, respectively. 
         FIG. 8  is a perspective view from below according to the arrow VIII of  FIG. 1 . 
         FIGS. 9 and 10  are partial cross-sections according to the line IX-IX of  FIG. 1  illustrating a locking device in an unlocked position and a locked position, respectively. 
         FIG. 11  is a perspective view of a second embodiment of a chair according to the present invention with the seat removed. 
         FIGS. 12 and 13  are cross-section taken along the line XII-XII of  FIG. 11  in the rest position and in the position of maximum backward inclination, respectively. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIGS. 1 and 2 , numeral  10  indicates a chair according to an embodiment of the present invention. The chair  10  comprises a base structure  12 , a seat  14  and a backrest  16 . The chair  10  comprises a synchronization mechanism  18 , which allows a synchronized movement of the seat  14  and the backrest  16  in the manner that will be described below. 
     In the embodiment illustrated by way of example in the figures, the base structure  12  comprises a rotatable and height-adjustable central column  20 , connected to a plurality of radial arms  22  carrying respective pivoting wheels  24 . The present invention is, however, not limited to a chair with a base structure of this type. The solution according to the present invention can also be applied to chairs with four legs or with a cantilever frame. 
     The synchronizing mechanism  18  comprises a support  26  fixed to the base structure  12 . The support  26  can be formed of aluminum or any other rigid material. The support  26  comprises a central base  28  from which two front side arms  30 ′ and two rear side arms  30 ″ extend. The side arms  30 ′,  30 ″ protrude laterally outwards from the central base  28 . The front and rear side arms  30 ′,  30 ″ have respective transverse portions  32 ′,  32 ″ and respective longitudinal portions  34 ′,  34 ″. 
     The synchronization mechanism  18  comprises two loop-shaped elastic elements  36  spaced apart in the transverse direction. With reference to  FIG. 3 , each loop-shaped elastic element  36  comprises a lower portion  38  fixed to the support  26 , an upper portion  40  fixed to the seat  14 , a front elastic portion  42  and a rear elastic portion  44 . Each loop-shaped elastic element  36  is made from a single piece of molded plastic material. The lower portion  38  of each loop-shaped elastic element  36  comprises two fastening elements  46 ′,  46 ″, which are fixed to respective side arms  30 ′,  30 ″. In the illustrated example, each fastening element  46 ′,  46 ′ comprises a transverse portion  48 ′,  48 ″ and a longitudinal portion  50 ′,  50 ″. 
     The transverse portions  48 ′,  48 ″ engage respective transverse portions  32 ′,  32 ″ of the side arms  30 ′,  30 ″ and the longitudinal portions  50 ′,  50 ″ of the fastening elements  46 ′,  46 ″ engage respective longitudinal portions  34 ′,  34 ″ of the side arms  30 ′,  30 ″. Preferably, the fastening elements  46 ′,  46 ″ have a U-shaped cross-section and snap engage the respective side arms  30 ′,  30 ″. 
     The upper portion  40  of each loop-shaped elastic element  36  has the shape of a longitudinal rectilinear bar, parallel to the longitudinal portions  50 ′,  50 ″ of the respective fastening elements  46 ′,  46 ″. 
     The front elastic portion  42  has an upper end integrally connected to a front end of the upper portion  40  and a lower end integrally connected to a front end of the longitudinal portion  50 ′. The rear elastic portion  44  has an upper end integrally connected to a rear end of the upper portion  40  and a lower end integrally connected to a rear end of the longitudinal portion  50 ″. 
     The rear elastic portion  44  of each loop-shaped elastic element  36  has a rear projection  52  integrally connected with the curved part of the rear elastic portion  44 . The rear projection  52  extends in the longitudinal direction and protrudes rearward from the respective loop-shaped elastic element  36 . 
     The rear projections  52  of the loop-shaped elastic elements  36  are fixed to respective L-shaped lower arms  54  of the backrest  16 . In the illustrated example, the L-shaped lower arms  54  protrude downwards from a lower edge of the backrest  16  and have respective hollow horizontal portions  56  in which respective rear projections  52  are inserted. The rear projections  52  are fixed to respective arms  54  by transverse screws  58 . In the example illustrated in the figures, the backrest  16  has a perimeter frame  60  of plastic material and the L-shaped lower arms  54  are integrally connected at their upper ends with the lower side of the frame  60 . A sheet of flexible material  62 , stretched over the frame  60 , forms the support surface of the backrest  16 . Alternatively, the backrest  16  could be formed of a shaped panel of plastic material. In an alternative embodiment, the backrest  16  (or the frame  60  of the backrest  16 ) could be integrally connected with the loop-shaped elastic elements  36 . 
     The seat  14  comprises a seat support panel  64  and a padding  66  fixed on the upper surface of the seat support panel  64 . The seat support panel  64  has two longitudinal rectilinear ribs  68  integrally formed on the lower surface of the seat support panel  64  and spaced apart in the transverse direction. The longitudinal rectilinear ribs  68  rest on the respective upper portions  40  of the loop-shaped elastic elements  36 . The seat support panel  64  is fixed to the two upper portions  40  of the loop-shaped elastic elements  36 , for example by means of screws (not illustrated). 
     With reference to  FIGS. 6 and 7 , the chair  10  comprises a limit stop device  70  operatively arranged between the seat  14  and the support  26 . The limit stop device  70  comprises an upright  72 , which extends upwards from the central base  28  of the support  26 . The central upright  72  has an upper head with a support surface  74  facing the lower surface of the seat support panel  64 . The upright  72  has a slot  76  elongated in an essentially vertical direction. The slot  76  is engaged by a transverse pin  78  movable along the slot  76 . The transverse pin  78  is fixed to two walls  80  projecting downwards, integrally formed with the seat support panel  64 . The two walls  80  are arranged laterally on opposite sides of the upright  72 . The ends of the transverse pin  78  engage two aligned holes of the walls  80 . 
     With reference to  FIGS. 8-10 , the chair  10  comprises a locking device  82  operable by the user to lock or unlock the movement of the seat and backrest. The locking device  82  comprises a housing  84  fixed to the lower surface of the seat support panel  64 . A locking pin  86  is movable within the housing  84  in a longitudinal direction, between an unlocked position, illustrated in  FIG. 9  and a locked position, illustrated in  FIG. 10 . The locking pin  86  is connected via a flexible cable  90  to a control device  92 , equipped with a button  94  operable by the user. The control device  92  selects the operative position of the locking pin  86  via the flexible cable  90 . In the locked position, the locking pin  86  engages a locking seat  88  formed in the lower part of the head of the upright  72 . In the unlocked position, the locking pin  86  is disengaged from the locking seat  88 . 
     The operation of the chair according to the present invention is as follows. 
     Each of the two loop-shaped elastic elements  36 , from a kinematic point of view, is equivalent to an articulated parallelogram. The front and rear elastic portions  42 ,  44  maintain the loop-shaped elastic element  36  in a rest position. In the rest position, the backrest  16  is in an upright position and the seat  14  is in a lowered position. In the rest position, the seat  14  rests on the upper support surface  74  of the upright  72 . 
       FIG. 4  shows a side view of the resting position of the chair  10 . In this condition, the elastic portions  42 ,  44  of the loop-shaped elastic elements  36  are undeformed. A backward thrust applied by the user against the backrest  16  causes inclination of the backrest  16 , as shown in  FIG. 5 . The backward movement of the backrest  16  elastically deforms the elastic portions  44  of the loop-shaped elastic elements  36 . Due to the elastic deformation of the rear elastic portions  44 , the upper portions  40  of the loop-shaped elastic elements  36  move upwards and elastically deform the elastic portions  42 . Comparing  FIGS. 4 and 5 , it can be noted that, during the movement from the undeformed position of  FIG. 4  to the deformed position of  FIG. 5 , the upper portion  40  of each loop-shaped elastic element moves upwards, while remaining essentially parallel to itself, as in an articulated parallelogram equipped with two rigid rods hinged to the seat and to the base. The two elastic portions  40 ,  42  are kinematically equivalent to the two rods of an articulated parallelogram. The upper portion  40  and the lower portion  38  of each loop-shaped elastic element  36  remain undeformed. The only parts of the loop-shaped elastic elements  36  which deform are the elastic portions  42 ,  44 . 
     As can be seen from  FIGS. 4 and 5 , the movement of backward inclination of the backrest  16  is synchronized with an upward movement of the seat  14 . When the backrest  16  is in the position of maximum backward inclination, the seat  14  is in the highest position, and when the backrest  16  is in the upright position, the seat  14  is in the lowest position. To backwardly-incline the backrest  16 , the user must apply a reverse thrust proportional to the weight applied on the seat  14 . Therefore, the reaction that the backrest  16  applies to the user&#39;s back is proportional to the weight of the user. 
     As is visible in  FIGS. 6 and 7 , the limit stop device  70  limits the stroke of the seat  14 . In the absence of a reverse thrust on the backrest, the seat  14  rests on the surface  74  of the upright  72 . In this position, the seat  14  is in the lowest position. In this position, the transverse pin  78  is at the lower end of the slot  76 . In the position of maximum backward inclination of the backrest, the transverse pin  78  comes into abutment against the upper end of the slot  76 , as shown in  FIG. 7 . The limit stop device  70  limits the further upward movement of the seat  14  and, consequently, prevents further backward inclination of the backrest  16 . 
     When the user gets up from the chair  10 , the elastic portions  42 ,  44  return to their undeformed position and return the seat  14  to the lowered position and the backrest  16  to the upright position. The elasticity of the mechanism is provided by the intrinsic elastic properties of the material forming the loop-shaped elastic elements  36 . Elastic components are not necessary to provide the return action of the seat and the backrest into the rest position. 
     The locking device  82  allows locking of the backward movement of the backrest  16  and the upward movement of the seat  14 . Indeed, as shown in  FIG. 10 , when the locking pin  86  engages the seat  88  of the upright  72 , the seat  14  is locked with respect to the rigid support  26 . Consequently, the upward movement of the seat  14  and the backward-inclined movement of the backrest  16  are prevented. 
     A second embodiment of the limit stop device  70  is shown in  FIGS. 11, 12 and 13 . In these figures the elements corresponding to those previously described are indicated by the same reference numbers. In the embodiment of  FIGS. 11-13  each of the loop-shaped elastic elements  36  of the synchronization mechanism  18  comprises a respective limit stop device  70 . Each limit stop device  70  comprises a stop element  96  fixed to or integrally formed with one of the lower portion  38  or upper portion  40  of the respective loop-shaped elastic element  36  and engaging a longitudinal slot  98  formed in the other of the upper portion  40  or lower portion  38 . The stop elements  96  extend vertically and engage with longitudinal play the respective slots  98 . 
     In the embodiment shown in the drawings, the stop elements  96  are fixed to or integrally formed with the respective lower portions  38  of the loop-shaped elastic elements  36  and engage respective longitudinal slots  98  formed in the respective upper portions  40 . However, the arrangement could be reversed, that is the stop elements  96  could be fixed to or integrally formed with the respective upper portions  40  and engage respective longitudinal slots  98  formed in the lower portions  38 . 
     As described above with reference to the first embodiment, the movements of the backrest  16  and seat  14  are synchronized with each other. When the backrest  16  is in the position of maximum backward inclination the seat  14  is in the highest position and when the backrest  16  is in the upright position the seat  14  is in the lowest position.  FIG. 12  shows the rest configuration in which the seat  14  is in the lowest position and the backrest is in the position of maximum forward inclination. In this position the lower surface of the seat  14  rests on the upper surfaces  100  of the stop elements  96 , thereby defining a first stop position for the seat/backrest assembly. 
     As shown in  FIG. 13 , in the position of maximum backward inclination of the backrest  16 , front surfaces  102  of the stop elements  96  abut against front ends of the respective longitudinal slots  98 . In this position the stop elements  96  prevent a further backward inclination of the backrest  16  and define a second stop position for the seat/backrest assembly. In the second stop position the seat is in most raised position and it is raised from the upper surfaces  100  of the stop elements  96 . 
     The embodiment of  FIGS. 11-13  is advantageous in particular because the loop-shaped elastic elements  38  with the respective stop elements can be integrally formed by injection molding and do not require assembly steps. 
     Of course, without prejudice to the principle of the invention, the details of construction and the embodiments can be widely varied with respect to those described and illustrated, without thereby departing from the scope of the invention as defined by the claims that follow.