Patent Publication Number: US-8991924-B2

Title: Chair with tilting backrest

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of Italian patent application serial number TO2011A000204, filed Mar. 8, 2011, which is herein incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a chair with a tilting backrest comprising two flexible supporting sectional elements that can undergo elastic deformation under a thrust backwards applied by the user. 
     2. Description of the Related Art 
     The document No. EP-A-2110051 filed in the name of the present applicant describes a chair with a tilting backrest, comprising two ribbed supporting sectional elements set at a distance from one another in a transverse direction and connected to a base by means of a transverse supporting element, wherein each of the ribbed supporting sectional elements is substantially L-shaped, with a seat portion, a backrest portion, and a rounded portion for radiusing between the seat portion and the backrest portion. A material substantially in the form of a sheet extends between said supporting sectional elements and forms a seat and a backrest. Each of said ribbed supporting sectional elements is provided with a plurality of through notches set at a distance from one another that form respective points of localized deflection that enable a deflection of the supporting sectional element in a vertical plane. The notches have opposite surfaces that come into contact with one another in the position of maximum inclination so as to limit the maximum amount of bending backwards of the sectional element. 
     Another type of chair with tilting backrest is described in the document No. U.S. Pat. No. 4,856,846, which illustrates an elastically compliant backrest that comprises some transverse ribbings that are separated from one another by spaces and that are connected to one another by connectors in such a way that the ribbings can turn with respect to one another about horizontal axes. 
     One of the drawbacks of the chairs of a known type is that the through notches that close during bending backwards of the backrest could pinch the user or his/her garments. Moreover, the open space of the notches is visible in a transverse direction and gives the impression that the notches are dangerous points of failure. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a chair that will enable the drawbacks of the prior art to be overcome and that will have a styling that is more technically valid and solid as compared to chairs of a known type. 
     According to the present invention, the above object is achieved by a chair having the characteristics forming the subject of claim  1 . 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described in detail with reference to the attached drawings, which are provided purely by way of non-limiting example and in which: 
         FIGS. 1 and 2  are, respectively, a perspective view and a side view of a first embodiment and a second embodiment of a chair according to the present invention; 
         FIGS. 3 and 4  are enlarged perspective views of the parts indicated, respectively, by the arrows III and IV in  FIGS. 1 and 2 ; and 
         FIGS. 5 ,  6  and  7  are front and rear views according to the arrow V of  FIG. 3  illustrating various possible shapes of the notches. 
     
    
    
     DETAILED DESCRIPTION 
     With reference to  FIG. 1 , designated by  10  is a chair according to a first embodiment of the present invention. The chair  10  comprises a base structure  12  including a vertical upright  14  that rests on the floor by means of a plurality of radial arms  16 . The central upright  14 , which is possibly height-adjustable, carries at its top end a support  18 , provided, for example, with two pairs of radial arms  20 . 
     The chair  10  comprises two supporting sectional elements  22  forming the lateral edges of the chair  10 , fixed to the outer ends of the radial arms  20 . The two supporting sectional elements  22  are parallel to and set at a distance from one another in a transverse direction. The two supporting sectional elements  22  are preferably specular, and each of them is substantially L-shaped, with a seat portion  22   a , a backrest portion  22   b , and an arched radiusing portion  22   c , which extends between the seat portion  22   a  and the backrest portion  22   b.    
     Each supporting sectional element  22  is preferably constituted by a monolithic element made of injection-moulded plastic material. Each supporting sectional element  22  is provided with a ribbing  24  that extends in a vertical plane, obtained integrally with the respective supporting sectional element  22 . The ribbing  24  extends along the radiusing portion  22   c  and on at least one part of the seat portion  22   a  and of the backrest portion  22   b . The ribbing  24  extends on the underside of the seat portion  22   a  and on the rear side of the backrest portion  22   b.    
     In the embodiment of  FIG. 1 , the chair  10  comprises a flexible sheet  26  of fabric, mesh, or the like, which is stretched between the two lateral supporting sectional elements  22  and forms the seat and the backrest of the chair. The lateral edges of the flexible sheet  26  can be fixed within respective external grooves of the supporting sectional elements  12 , as described in the document EP-A-2110051 filed in the name of the present applicant. 
     With reference to  FIGS. 1 and 3 , the ribbing  24  of each supporting sectional element  22  is provided with a plurality of through notches  28  set at a distance from one another along the longitudinal axis of the ribbing  24 . The notches  28  form respective points of localized bending of the supporting sectional elements  22 . At each notch  28 , the supporting sectional element  22  is able to perform a movement of bending. The notches  28  are set apart in a longitudinal direction by stretches  30  in which the ribbing  24  is continuous. The supporting sectional element  22  in the stretches  30  is basically stiff in regard to movements of bending in a vertical plane. The notches  28  form hinge points between substantially stiff contiguous sections of the supporting sectional element  22 . 
     The supporting sectional elements  22  are elastically deformable backwards under a thrust applied by the back of the user. The backrest oscillates backwards thanks to bending of the supporting sectional elements  22  at the notches  28 . Return from the bent position to the resting position occurs as a result of the elastic return of the material constituting the supporting sectional elements  22 . 
       FIGS. 2 and 4  illustrate a second embodiment of the chair  10  according to the present invention. The elements corresponding to the ones described previously are designated by the same reference numbers. 
     In this case, the seat and the backrest of the chair  10  are formed by a shaped thin plate  32  of injection-moulded plastic material, formed integrally with the lateral supporting sectional elements  22 . Also in this case, the supporting sectional elements  22  are provided with respective ribbings  24  provided with notches  28  that form points of localized bending of the supporting sectional elements  22 . 
     In the variant of  FIGS. 2 and 4  the base structure  12  of the chair  10  can be formed by a metal frame with four legs  34 , having two lateral elements  36 , fixed to which are the respective supporting sectional elements  22 . 
     Shown in  FIG. 4  is a seat  38  formed at the base of the ribbing  24 , in which there can be housed an elastic member, constituted for example by a bar of metal material with high elasticity (for example, spring steel) for enhancing the characteristics of elastic return of the supporting sectional element  22 . 
     The elastic member can of course also be provided in the embodiment of  FIG. 1 . In this case, the elastic member can be housed in a seat made in the same groove as the one in which the edge of the fabric is inserted. 
       FIGS. 5 ,  6  and  7  illustrate some possible shapes of the notches  28 . Each notch  28  has a first contact surface  40  and a second contact surface  42 . In the position of maximum inclination backwards of the backrest the first and second contact surfaces  40 ,  42  come to bear on one another to stop bending backwards of the sectional element  24 . 
     Designated by P in  FIGS. 5-7  is the trace of a vertical plane parallel to the longitudinal axis of the chair. The projections of the contact surfaces  40 ,  42  in the plane P are designated by  40 ′ and  42 ′, respectively. 
     The shape of the notches  28  is such that the projections  40 ′,  42 ′ of the first and second contact surfaces  40 ,  42  in the plane P are at least partially superimposed on one another. In this way, a visual communication through the notches  28  in a direction orthogonal to the plane P is prevented. 
     The shape of the contact surfaces  40 ,  42  may present numerous variants. By way of example, in  FIGS. 5 ,  6  and  7  notches  28  are shown, the contact surfaces  40 ,  42  of which in a plane orthogonal to said plane P are substantially V-shaped, Ω-shaped, and shaped like an inclined bar. The shapes illustrated in  FIGS. 5-7  are to be considered merely as non-exhaustive examples. For the purposes of the present invention, any other shape of the notches that produces an at least partial superposition of the projections  40 ′,  42 ′ can be used. 
     This shape of the notches enables considerable reduction of the risk of squeezing or pinching for the user. At the same time, the aesthetic appearance of the chair is improved in so far as the notches no longer have the appearance of dangerous points of failure. The fact that it is not possible to see through the notches bestows upon the chair an appearance that is more technically valid and sturdy. 
     A chair that uses the notches described in the present application can be provided also in ways alternative to the ones illustrated in  FIGS. 1-7 . 
     The seat, the backrest, and the elastic joints (provided with the notches) may not be moulded integrally. 
     Alternatively, the seat and backrest could be discrete components; the notches could be made in portions of just the seat, just the backrest, or both of them. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.