Abstract: A chair backrest mounting device includes a main body, a middle fixing seat, and two side fixing seats. The main body is made of a flexible material. The middle and side fixing seats are made of a rigid material and embedded in a middle portion and two opposite end portions of the main body, respectively, so that the chair backrest mounting device can maintain sufficient flexibility and deformability to bear forces applied thereto in different angular directions, and sufficient rigidity to avoid easy elastic fatigue and breaking of the main body. Moreover, joint faces between the flexible main body and each of the rigid middle fixing seat and side fixing seats are non-flat faces to provide increased contact area and enhanced joining strength.

Abstract: A chair backrest mounting bracket includes a middle fixing section made of a material with high rigidity and having an axially extended and internally threaded central mounting hole, the middle fixing section being connectable to a backrest support of a chair by threading a middle bolt through the backrest support into the internally threaded central mounting hole; a plurality of side fixing sections made of a material with high rigidity and located outside the middle fixing section for mounting to a rear surface of a backrest of the chair; and an elastically deformable connecting section located between the middle fixing section and each of the side fixing sections. With the elastic connecting sections, the backrest connected to the backrest support via the side and the middle fixing sections is allowed to elastically deflect in multiple directions relative to the backrest support, making the backrest more comfortable for leaning.

Abstract: A chair backrest mounting bracket includes a highly elastic main body for disposing between a chair backrest and a backrest support; a rigid middle fixing seat embedded in a middle section of the main body and having a centered middle mounting hole for a middle bolt to extend therethrough into a threaded hole correspondingly provided on the backrest support; and a plurality of rigid side fixing seats symmetrically embedded in opposite outer ends of the main body and having a centered side mounting hole each for a side bolt to extend therethrough into a threaded hole correspondingly provided on the chair backrest. Since the main body is elastically deformable under an externally applied force, the chair backrest connected to the backrest support via the mounting bracket is allowed to freely elastically deflect relative to the backrest support.